C#'s 101 LINQ Samples translated to Clojure
Clojure
Latest commit f5561d9 Jan 14, 2016 @mythz Update README.md

README.md

101 LINQ Samples in Clojure

Port of C#'s' 101 LINQ Samples translated into Clojure.

Compare Clojure to other LINQ examples written in:

Running the examples

You can choose to run specific examples by commenting the sections you're not interested in core.clj -main.

Execute and display the results of all the examples with:

lein run

Contents

The samples below mirrors the C# LINQ samples layout with the names of the top-level Clojure methods matching their corresponding C# examples.

LINQ - Restriction Operators / MSDN C#

LINQ - Projection Operators / MSDN C#

LINQ - Partitioning Operators / MSDN C#

LINQ - Ordering Operators / MSDN C#

LINQ - Grouping Operators / MSDN C#

LINQ - Set Operators / MSDN C#

LINQ - Conversion Operators / MSDN C#

LINQ - Element Operators / MSDN C#

LINQ - Generation Operators / MSDN C#

LINQ - Quantifiers / MSDN C#

LINQ - Aggregate Operators / MSDN C#

LINQ - Miscellaneous Operators / MSDN C#

LINQ - Query Execution / MSDN C#

LINQ - Join Operators / MSDN C#

Side-by-side - C# LINQ vs Clojure

For a side-by-side comparison, the original C# source code is displayed above the equivalent Clojure translation.

  • The Output shows the console output of running the Clojure sample.
  • Outputs ending with ... illustrates only a partial response is displayed.
  • The source-code for C# and Clojure utils used are included once under the first section they're used in.
  • The C# ObjectDumper util used is downloadable from MSDN - ObjectDumper.zip

LINQ - Restriction Operators

linq1: Where - Simple 1

//c#
public void Linq1()
{
    int[] numbers = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };

    var lowNums =
        from n in numbers
        where n < 5
        select n;

    Console.WriteLine("Numbers < 5:");
    foreach (var x in lowNums)
    {
        Console.WriteLine(x);
    }
}
;;clojure
(defn linq1 []
  (let [numbers [5 4 1 3 9 8 6 7 2 0]
        low-numbers (filter #(< % 5) numbers)]
    (println "Numbers < 5:")
    (doseq [n low-numbers]
      (println n))))

Output

Numbers < 5:
4
1
3
2
0

linq2: Where - Simple 2

//c#
public void Linq2()
{
    List<Product> products = GetProductList();

    var soldOutProducts =
        from p in products
        where p.UnitsInStock == 0
        select p;

    Console.WriteLine("Sold out products:");
    foreach (var product in soldOutProducts)
    {
        Console.WriteLine("{0} is sold out!", product.ProductName);
    }
}
;;clojure
(defn linq2 []
  (let [products products-list
        sold-out-products (for [p products
                                :when (= 0 (:units-in-stock p))]
                            p)]
    (println "Sold out products:")
    (doseq [p sold-out-products]
      (println (:product-name p) " is sold out"))))

Output

Sold out products:
Chef Anton's Gumbo Mix  is sold out
Alice Mutton  is sold out
Thüringer Rostbratwurst  is sold out
Gorgonzola Telino  is sold out
Perth Pasties  is sold out

linq3: Where - Simple 3

//c#
public void Linq3()
{
    List<Product> products = GetProductList();

    var expensiveInStockProducts =
        from p in products
        where p.UnitsInStock > 0 && p.UnitPrice > 3.00M
        select p;

    Console.WriteLine("In-stock products that cost more than 3.00:");
    foreach (var product in expensiveInStockProducts)
    {
        Console.WriteLine("{0} is in stock and costs more than 3.00.", product.ProductName);
    }
}
;;clojure
(defn linq3 []
  (let [products products-list
        expensive-in-stock-products
        (for [p products-list
              :when (and
                     (> (:units-in-stock p) 0)
                     (> (:unit-price p) 3))]
          p)]
    (println "In-stock products that cost more than 3.00:")
    (doseq [p expensive-in-stock-products]
      (println (:product-name p) "is in stock and costs more than 3.00"))))

Output

In-stock products that cost more than 3.00:
Chai is in stock and costs more than 3.00
Chang is in stock and costs more than 3.00
Aniseed Syrup is in stock and costs more than 3.00
Chef Anton's Cajun Seasoning is in stock and costs more than 3.00
Grandma's Boysenberry Spread is in stock and costs more than 3.00

linq4: Where - Drilldown

//c#
public void Linq4()
{
    List<Customer> customers = GetCustomerList();

    var waCustomers =
        from c in customers
        where c.Region == "WA"
        select c;

    Console.WriteLine("Customers from Washington and their orders:");
    foreach (var customer in waCustomers)
    {
        Console.WriteLine("Customer {0}: {1}", customer.CustomerID, customer.CompanyName);
        foreach (var order in customer.Orders)
        {
            Console.WriteLine("  Order {0}: {1}", order.OrderID, order.OrderDate);
        }
    }
}
;;clojure
(defn linq4 []
  (let [customers customers-list
        wa-customers (filter #(= (:region %) "WA") customers)]
    (println "Customers from Washington and their orders:")
    (doseq [c wa-customers]
      (println "Customer" (:customer-id c) ": " (:company-name c) ":")
      (doseq [o (:orders c)]
        (println "    Order" (:order-id o) ":" (:order-date o))))))

Output

Customers from Washington and their orders:
Customer LAZYK :  Lazy K Kountry Store :
    Order 10482 : #<DateTime 1997-03-21T00:00:00.000-05:00>
    Order 10545 : #<DateTime 1997-05-22T00:00:00.000-04:00>
Customer TRAIH :  Trail's Head Gourmet Provisioners :
    Order 10574 : #<DateTime 1997-06-19T00:00:00.000-04:00>
    Order 10577 : #<DateTime 1997-06-23T00:00:00.000-04:00>
    Order 10822 : #<DateTime 1998-01-08T00:00:00.000-05:00>
...

linq5: Where - Indexed

//c#
public void Linq5()
{
    string[] digits = { "zero", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine" };

    var shortDigits = digits.Where((digit, index) => digit.Length < index);

    Console.WriteLine("Short digits:");
    foreach (var d in shortDigits)
    {
        Console.WriteLine("The word {0} is shorter than its value.", d);
    }
}
;;clojure
(defn linq5 []
  (let [digits ["zero" "one" "two" "three" "four" "five" "six" "seven" "eight" "nine"]
        short-digits
        (for [[i digit] (map-indexed vector digits)
              :when (> i (count digit))]
          digit)]
    (println "Short digits:")
    (doseq [d short-digits]
      (println "The word" d "is shorter than its value"))))

Output

Short digits:
The word five is shorter than its value
The word six is shorter than its value
The word seven is shorter than its value
The word eight is shorter than its value
The word nine is shorter than its value

LINQ - Projection Operators

linq6: Select - Simple 1

//c#
public void Linq6()
{
    int[] numbers = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };

    var numsPlusOne =
        from n in numbers
        select n + 1;

    Console.WriteLine("Numbers + 1:");
    foreach (var i in numsPlusOne)
    {
        Console.WriteLine(i);
    }
}
;;clojure
(defn linq6 []
  (let [numbers [5 4 1 3 9 8 6 7 2 0]
        nums-plus-one (map inc numbers)]
    (println "Numbers + 1:")
    (doseq [n nums-plus-one] (println n))))

Output

Numbers + 1:
6
5
2
4
10
9
7
8
3
1

linq7: Select - Simple 2

//c#
public void Linq7()
{
    List<Product> products = GetProductList();

    var productNames =
        from p in products
        select p.ProductName;

    Console.WriteLine("Product Names:");
    foreach (var productName in productNames)
    {
        Console.WriteLine(productName);
    }
}
;;clojure
(defn linq7 []
  (let [products products-list
        product-names (map #(:product-name %) products)]
    (println "Product Names:")
    (doseq [x product-names] (println x))))

Output

Product Names:
Chai
Chang
Aniseed Syrup
Chef Anton's Cajun Seasoning
Chef Anton's Gumbo Mix
...

linq8: Select - Transformation

//c#
public void Linq8()
{
    int[] numbers = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };
    string[] strings = { "zero", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine" };

    var textNums =
        from n in numbers
        select strings[n];

    Console.WriteLine("Number strings:");
    foreach (var s in textNums)
    {
        Console.WriteLine(s);
    }
}
;;clojure
(defn linq8 []
  (let [numbers [5 4 1 3 9 8 6 7 2 0]
        strings ["zero" "one" "two" "three" "four" "five" "six" "seven" "eight" "nine"]
        text-nums (map strings numbers)]
    (println "Number strings:")
    (doseq [n text-nums] (println n))))

Output

Number strings:
five
four
one
three
nine
eight
six
seven
two
zero

linq9: Select - Anonymous Types 1

//c#
public void Linq9()
{
    string[] words = { "aPPLE", "BlUeBeRrY", "cHeRry" };

    var upperLowerWords =
        from w in words
        select new { Upper = w.ToUpper(), Lower = w.ToLower() };

    foreach (var ul in upperLowerWords)
    {
        Console.WriteLine("Uppercase: {0}, Lowercase: {1}", ul.Upper, ul.Lower);
    }
}
;;clojure
(defn linq9 []
  (let [words ["aPPLE", "BlUeBeRrY", "cHeRry"]
        upper-lower-words
        (for [w words] { :lower (str/lower-case w), :upper (str/upper-case w)})]    
    (doseq [ul upper-lower-words]
      (println "Uppercase:" (:upper ul) ", Lowercase:" (:lower ul)))))

Output

Uppercase: APPLE , Lowercase: apple
Uppercase: BLUEBERRY , Lowercase: blueberry
Uppercase: CHERRY , Lowercase: cherry

linq10: Select - Anonymous Types 2

//c#
public void Linq10()
{
    int[] numbers = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };
    string[] strings = { "zero", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine" };

    var digitOddEvens =
        from n in numbers
        select new { Digit = strings[n], Even = (n % 2 == 0) };

    foreach (var d in digitOddEvens)
    {
        Console.WriteLine("The digit {0} is {1}.", d.Digit, d.Even ? "even" : "odd");
    }
}
;;clojure
(defn linq10 []
  (let [numbers [5 4 1 3 9 8 6 7 2 0]
        strings ["zero" "one" "two" "three" "four" "five" "six" "seven" "eight" "nine"]
        digit-odd-evens
        (for [n numbers] {:digit (strings n), :even (= (mod n 2) 0)})]
    (doseq [d digit-odd-evens]
      (println "The digit" (:digit d) "is" (if (:even d) "even" "odd")))))

Output

The digit five is odd
The digit four is even
The digit one is odd
The digit three is odd
The digit nine is odd
The digit eight is even
The digit six is even
The digit seven is odd
The digit two is even
The digit zero is even

linq11: Select - Anonymous Types 3

//c#
public void Linq11()
{
    List<Product> products = GetProductList();

    var productInfos =
        from p in products
        select new { p.ProductName, p.Category, Price = p.UnitPrice };

    Console.WriteLine("Product Info:");
    foreach (var productInfo in productInfos)
    {
        Console.WriteLine("{0} is in the category {1} and costs {2} per unit.", productInfo.ProductName, productInfo.Category, productInfo.Price);
    }
}
;;clojure
(defn linq11 []
  (let [products products-list
        product-infos
        (for [p products]
          {:product-name (:product-name p), 
           :category (:category p), 
           :price (:unit-price p)})]
    (println "Product Info:")
    (doseq [p product-infos]
      (println (:product-name p) "is in the category" (:category p) 
               "and costs" (:price p)))))

Output

Product Info:
Chai is in the category Beverages and costs 18.0
Chang is in the category Beverages and costs 19.0
Aniseed Syrup is in the category Condiments and costs 10.0
...

linq12: Select - Indexed

//c#
public void Linq12()
{
    int[] numbers = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };

    var numsInPlace = numbers.Select((num, index) => new { Num = num, InPlace = (num == index) });

    Console.WriteLine("Number: In-place?");
    foreach (var n in numsInPlace)
    {
        Console.WriteLine("{0}: {1}", n.Num, n.InPlace);
    }
}
;;clojure
(defn linq12 []
  (let [numbers [5 4 1 3 9 8 6 7 2 0]
        nums-in-place
        (map-indexed (fn [i num] {:num num, :in-place (= num i)}) numbers)]
    (println "Number: In-place?")
    (doseq [n nums-in-place]
      (println (:num n) ":" (:in-place n)))))

Output

Number: In-place?
5 : false
4 : false
1 : false
3 : true
9 : false
8 : false
6 : true
7 : true
2 : false
0 : false

linq13: Select - Filtered

//c#
public void Linq13()
{
    int[] numbers = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };
    string[] digits = { "zero", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine" };

    var lowNums =
        from n in numbers
        where n < 5
        select digits[n];

    Console.WriteLine("Numbers < 5:");
    foreach (var num in lowNums)
    {
        Console.WriteLine(num);
    }
}
;;clojure
(defn linq13 []
  (let [numbers [5 4 1 3 9 8 6 7 2 0]
        digits ["zero" "one" "two" "three" "four" "five" "six" "seven" "eight" "nine"]
        low-nums (for [n numbers 
                       :when (< n 5)] 
                   (digits n))]
    (println "Numbers < 5:")
    (doseq [n low-nums] (println n))))

Output

Numbers < 5:
four
one
three
two
zero

linq14: SelectMany - Compound from 1

//c#
public void Linq14()
{
    int[] numbersA = { 0, 2, 4, 5, 6, 8, 9 };
    int[] numbersB = { 1, 3, 5, 7, 8 };

    var pairs =
        from a in numbersA
        from b in numbersB
        where a < b
        select new { a, b };

    Console.WriteLine("Pairs where a < b:");
    foreach (var pair in pairs)
    {
        Console.WriteLine("{0} is less than {1}", pair.a, pair.b);
    }
}
;;clojure
(defn linq14 []
  (let [numbers-a [0 2 4 5 6 8 9]
        numbers-b [1 3 5 7 8]
        pairs (for [a numbers-a
                    b numbers-b
                    :when (< a b)]
                {:a a, :b b})]
    (println "Pairs where a < b:")
    (doseq [pair pairs]
      (println (:a pair) "is less than" (:b pair)))))

Output

Pairs where a < b:
0 is less than 1
0 is less than 3
0 is less than 5
0 is less than 7
0 is less than 8
2 is less than 3
2 is less than 5
2 is less than 7
2 is less than 8
4 is less than 5
4 is less than 7
4 is less than 8
5 is less than 7
5 is less than 8
6 is less than 7
6 is less than 8

linq15: SelectMany - Compound from 2

//c#
public void Linq15()
{
    List<Customer> customers = GetCustomerList();

    var orders =
        from c in customers
        from o in c.Orders
        where o.Total < 500.00M
        select new { c.CustomerID, o.OrderID, o.Total };

    ObjectDumper.Write(orders);
}
;;clojure
(defn linq15 []
  (let [customers customers-list
        orders
        (for [c customers
              o (:orders c)
              :when (< (:total o) 500)]
          {:customer-id (:customer-id c), 
           :order-id (:order-id o), 
           :total (:total o)})]
    (doseq [o orders] (println o))))

Output

{:customer-id ALFKI, :order-id 10702, :total 330.00M}
{:customer-id ALFKI, :order-id 10952, :total 471.20M}
{:customer-id ANATR, :order-id 10308, :total 88.80M}
{:customer-id ANATR, :order-id 10625, :total 479.75M}
...

linq16: SelectMany - Compound from 3

//c#
public void Linq16()
{
    List<Customer> customers = GetCustomerList();

    var orders =
        from c in customers
        from o in c.Orders
        where o.OrderDate >= new DateTime(1998, 1, 1)
        select new { c.CustomerID, o.OrderID, o.OrderDate };

    ObjectDumper.Write(orders);
}
;;clojure
(defn linq16 []
  (let [customers customers-list
        orders
        (for [c customers
              o (:orders c)
              :when (time/after? (:order-date o) (time/date-time 1998 1 1))]
          {:customer-id (:customer-id c), 
           :order-id (:order-id o), 
           :order-date (:order-date o)})]
    (doseq [o orders] (println o))))

Output

{:customer-id ALFKI, :order-id 10835, :order-date #<DateTime 1998-01-15T00:00:00.000-05:00>}
{:customer-id ALFKI, :order-id 10952, :order-date #<DateTime 1998-03-16T00:00:00.000-05:00>}
{:customer-id ALFKI, :order-id 11011, :order-date #<DateTime 1998-04-09T00:00:00.000-04:00>}
{:customer-id ANATR, :order-id 10926, :order-date #<DateTime 1998-03-04T00:00:00.000-05:00>}
{:customer-id ANTON, :order-id 10856, :order-date #<DateTime 1998-01-28T00:00:00.000-05:00>}
...

linq17: SelectMany - from Assignment

//c#
public void Linq17()
{
    List<Customer> customers = GetCustomerList();

    var orders =
        from c in customers
        from o in c.Orders
        where o.Total >= 2000.0M
        select new { c.CustomerID, o.OrderID, o.Total };

    ObjectDumper.Write(orders);
}
;;clojure
(defn linq17 []
  (let [customers customers-list
        orders
        (for [c customers
              o (:orders c)
              :when (>= (:total o) 2000)]
          {:customer-id (:customer-id c), :order-id (:order-id o), :total (:total o)})]
    (doseq [o orders] (println o))))

Output

{:customer-id ANTON, :order-id 10573, :total 2082.00M}
{:customer-id AROUT, :order-id 10558, :total 2142.90M}
{:customer-id AROUT, :order-id 10953, :total 4441.25M}
{:customer-id BERGS, :order-id 10384, :total 2222.40M}
{:customer-id BERGS, :order-id 10524, :total 3192.65M}
...

linq18: SelectMany - Multiple from

//c#
public void Linq18()
{
    List<Customer> customers = GetCustomerList();

    DateTime cutoffDate = new DateTime(1997, 1, 1);

    var orders =
        from c in customers
        where c.Region == "WA"
        from o in c.Orders
        where o.OrderDate >= cutoffDate
        select new { c.CustomerID, o.OrderID };

    ObjectDumper.Write(orders);
}
;;clojure
(defn linq18 []
  (let [customers customers-list
        cutoff-date (time/date-time 1997 1 1)
        orders
        (for [c customers 
              :when (= (:region c) "WA")
              o (:orders c)
              :when (time/after? (:order-date o) cutoff-date)]
          {:customer-id (:customer-id c), :order-id (:order-id o)})]
    (doseq [o orders] (println o))))

Output

{:customer-id LAZYK, :order-id 10482}
{:customer-id LAZYK, :order-id 10545}
{:customer-id TRAIH, :order-id 10574}
{:customer-id TRAIH, :order-id 10577}
{:customer-id TRAIH, :order-id 10822}
{:customer-id WHITC, :order-id 10469}
{:customer-id WHITC, :order-id 10483}
{:customer-id WHITC, :order-id 10504}
{:customer-id WHITC, :order-id 10596}
{:customer-id WHITC, :order-id 10693}
{:customer-id WHITC, :order-id 10696}
{:customer-id WHITC, :order-id 10723}
{:customer-id WHITC, :order-id 10740}
{:customer-id WHITC, :order-id 10861}
{:customer-id WHITC, :order-id 10904}
{:customer-id WHITC, :order-id 11032}
{:customer-id WHITC, :order-id 11066}

linq19: SelectMany - Indexed

//c#
public void Linq19()
{
    List<Customer> customers = GetCustomerList();

    var customerOrders =
        customers.SelectMany(
            (cust, custIndex) =>
            cust.Orders.Select(o => "Customer #" + (custIndex + 1) +
                                    " has an order with OrderID " + o.OrderID));

    ObjectDumper.Write(customerOrders);
}
;;clojure
(defn linq19 []
  (let [customers customers-list
        customer-orders
        (for [[i c] (map-indexed vector customers)
              o (:orders c)]
          (str "Customer #" (inc i) " has an order with OrderID " (:order-id o)))]
    (doseq [x customer-orders] (println x))))

Output

Customer #1 has an order with OrderID 10643
Customer #1 has an order with OrderID 10692
Customer #1 has an order with OrderID 10702
Customer #1 has an order with OrderID 10835
Customer #1 has an order with OrderID 10952
Customer #1 has an order with OrderID 11011
Customer #2 has an order with OrderID 10308
Customer #2 has an order with OrderID 10625
Customer #2 has an order with OrderID 10759
Customer #2 has an order with OrderID 10926
...

LINQ - Partitioning Operators

linq20: Take - Simple

//c#
public void Linq20()
{
    int[] numbers = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };

    var first3Numbers = numbers.Take(3);

    Console.WriteLine("First 3 numbers:");

    foreach (var n in first3Numbers)
    {
        Console.WriteLine(n);
    }
}
;;clojure
(defn linq20 []
  (let [numbers [5 4 1 3 9 8 6 7 2 0]
        first-3-numbers (take 3 numbers)]
    (println "First 3 numbers:")
    (doseq [n first-3-numbers] (println n))))

Output

First 3 numbers:
5
4
1

linq21: Take - Nested

//c#
public void Linq21()
{
    List<Customer> customers = GetCustomerList();

    var first3WAOrders = (
        from c in customers
        from o in c.Orders
        where c.Region == "WA"
        select new { c.CustomerID, o.OrderID, o.OrderDate })
        .Take(3);

    Console.WriteLine("First 3 orders in WA:");
    foreach (var order in first3WAOrders)
    {
        ObjectDumper.Write(order);
    }
}
;;clojure
(defn linq21 []
  (let [customers customers-list
        first-3-wa-orders
        (take 3 
              (for [c customers
                    :when (= (:region c) "WA")
                    o (:orders c)]
                {:customer-id (:customer-id c),
                 :order-id (:order-id o),
                 :order-date (:order-date o)}))]
    (println "First 3 orders in WA:")
    (doseq [x first-3-wa-orders] (println x))))

Output

First 3 orders in WA:
{:customer-id LAZYK, :order-id 10482, :order-date #<DateTime 1997-03-21T00:00:00.000-05:00>}
{:customer-id LAZYK, :order-id 10545, :order-date #<DateTime 1997-05-22T00:00:00.000-04:00>}
{:customer-id TRAIH, :order-id 10574, :order-date #<DateTime 1997-06-19T00:00:00.000-04:00>}

linq22: Skip - Simple

//c#
public void Linq22()
{
    int[] numbers = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };

    var allButFirst4Numbers = numbers.Skip(4);

    Console.WriteLine("All but first 4 numbers:");
    foreach (var n in allButFirst4Numbers)
    {
        Console.WriteLine(n);
    }
}
;;clojure
(defn linq22 []
  (let [numbers [5 4 1 3 9 8 6 7 2 0]
        all-but-first-4-numbers (drop 4 numbers)]
    (println "All but first 4 numbers:")
    (doseq [n all-but-first-4-numbers] (println n))))

Output

All but first 4 numbers:
9
8
6
7
2
0

linq23: Skip - Nested

//c#
public void Linq23()
{
    List<Customer> customers = GetCustomerList();

    var waOrders =
        from c in customers
        from o in c.Orders
        where c.Region == "WA"
        select new { c.CustomerID, o.OrderID, o.OrderDate };

    var allButFirst2Orders = waOrders.Skip(2);

    Console.WriteLine("All but first 2 orders in WA:");
    foreach (var order in allButFirst2Orders)
    {
        ObjectDumper.Write(order);
    }
}
;;clojure
(defn linq23 []
  (let [customers customers-list
        all-but-first-2-orders
        (drop 2 
              (for [c customers
                       :when (= (:region c) "WA")
                      o (:orders c)]
                   {:customer-id (:customer-id c),
                      :order-id (:order-id o),
                      :order-date (:order-date o)}))]
    (println "All but first 2 orders in WA:")
    (doseq [o all-but-first-2-orders] (println o))))

Output

All but first 2 orders in WA:
{:customer-id TRAIH, :order-id 10574, :order-date #<DateTime 1997-06-19T00:00:00.000-04:00>}
{:customer-id TRAIH, :order-id 10577, :order-date #<DateTime 1997-06-23T00:00:00.000-04:00>}
{:customer-id TRAIH, :order-id 10822, :order-date #<DateTime 1998-01-08T00:00:00.000-05:00>}
{:customer-id WHITC, :order-id 10269, :order-date #<DateTime 1996-07-31T00:00:00.000-04:00>}
{:customer-id WHITC, :order-id 10344, :order-date #<DateTime 1996-11-01T00:00:00.000-05:00>}
{:customer-id WHITC, :order-id 10469, :order-date #<DateTime 1997-03-10T00:00:00.000-05:00>}
{:customer-id WHITC, :order-id 10483, :order-date #<DateTime 1997-03-24T00:00:00.000-05:00>}
{:customer-id WHITC, :order-id 10504, :order-date #<DateTime 1997-04-11T00:00:00.000-04:00>}
{:customer-id WHITC, :order-id 10596, :order-date #<DateTime 1997-07-11T00:00:00.000-04:00>}
{:customer-id WHITC, :order-id 10693, :order-date #<DateTime 1997-10-06T00:00:00.000-04:00>}
{:customer-id WHITC, :order-id 10696, :order-date #<DateTime 1997-10-08T00:00:00.000-04:00>}
{:customer-id WHITC, :order-id 10723, :order-date #<DateTime 1997-10-30T00:00:00.000-05:00>}
{:customer-id WHITC, :order-id 10740, :order-date #<DateTime 1997-11-13T00:00:00.000-05:00>}
{:customer-id WHITC, :order-id 10861, :order-date #<DateTime 1998-01-30T00:00:00.000-05:00>}
{:customer-id WHITC, :order-id 10904, :order-date #<DateTime 1998-02-24T00:00:00.000-05:00>}
{:customer-id WHITC, :order-id 11032, :order-date #<DateTime 1998-04-17T00:00:00.000-04:00>}
{:customer-id WHITC, :order-id 11066, :order-date #<DateTime 1998-05-01T00:00:00.000-04:00>}

linq24: TakeWhile - Simple

//c#
public void Linq24()
{
    int[] numbers = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };

    var firstNumbersLessThan6 = numbers.TakeWhile(n => n < 6);

    Console.WriteLine("First numbers less than 6:");
    foreach (var n in firstNumbersLessThan6)
    {
        Console.WriteLine(n);
    }
}
;;clojure
(defn linq24 []
  (let [numbers [5 4 1 3 9 8 6 7 2 0]
        first-numbers-less-than-6 (take-while #(< % 6) numbers)]
    (println "First numbers less than 6:")
    (doseq [n first-numbers-less-than-6] (println n))))

Output

First numbers less than 6:
5
4
1
3

linq25: TakeWhile - Indexed

//c#
public void Linq25()
{
    int[] numbers = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };

    var firstSmallNumbers = numbers.TakeWhile((n, index) => n >= index);

    Console.WriteLine("First numbers not less than their position:");
    foreach (var n in firstSmallNumbers)
    {
        Console.WriteLine(n);
    }
}
;;clojure
(defn linq25 []
  (let [numbers [5 4 1 3 9 8 6 7 2 0]
        first-small-numbers
        (for [[i num] (map-indexed vector numbers)
              :while (>= num i)]
          num)]
    (println "First numbers not less than their position:")
  (doseq [n first-small-numbers] (println n))))

Output

First numbers not less than their position:
5
4

linq26: SkipWhile - Simple

//c#
public void Linq26()
{
    int[] numbers = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };

    var allButFirst3Numbers = numbers.SkipWhile(n => n % 3 != 0);

    Console.WriteLine("All elements starting from first element divisible by 3:");
    foreach (var n in allButFirst3Numbers)
    {
        Console.WriteLine(n);
    }
}
;;clojure
(defn linq26 []
  (let [numbers [5 4 1 3 9 8 6 7 2 0]
        all-but-first-3-numbers (drop-while #(not= (mod % 3) 0) numbers)]
    (println "All elements starting from first element divisible by 3:")
    (doseq [n all-but-first-3-numbers] (println n))))

Output

All elements starting from first element divisible by 3:
3
9
8
6
7
2
0

linq27: SkipWhile - Indexed

//c#
public void Linq27()
{
    int[] numbers = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };

    var laterNumbers = numbers.SkipWhile((n, index) => n >= index);

    Console.WriteLine("All elements starting from first element less than its position:");
    foreach (var n in laterNumbers)
    {
        Console.WriteLine(n);
    }
}
;;clojure
(defn linq27 []
  (let [numbers [5 4 1 3 9 8 6 7 2 0]
        later-numbers
        (map (fn [[i num]] num)
             (drop-while (fn [[i num]] (>= num i)) (map-indexed vector numbers)))]
    (println "All elements starting from first element less than its position:")
    (doseq [n later-numbers] (println n))))

Output

All elements starting from first element less than its position:
1
3
9
8
6
7
2
0

LINQ - Ordering Operators

C# utils added

public class CaseInsensitiveComparer : IComparer<string>
{
    public int Compare(string x, string y)
    {
        return string.Compare(x, y, StringComparison.OrdinalIgnoreCase);
    }
}

Clojure utils added

(defn case-insensitive-compare [s1 s2]
  (compare (.toLowerCase s1) (.toLowerCase s2)))

(defn order-by-comparers [comparers xs]
  (sort-by
   pass-thru
   (fn [a1 a2]
     (nth (for [x (map #(% a1 a2) comparers)
                :when (not= x 0)] x)
          0 0))
   xs))

(defn order-by [fns xs]
  (sort-by (apply juxt fns) xs))

linq28: OrderBy - Simple 1

//c#
public void Linq28()
{
    string[] words = { "cherry", "apple", "blueberry" };

    var sortedWords =
        from w in words
        orderby w
        select w;

    Console.WriteLine("The sorted list of words:");
    foreach (var w in sortedWords)
    {
        Console.WriteLine(w);
    }
}
;;clojure
(defn linq28 []
  (let [words ["cherry" "apple" "blueberry"]
        sorted-words (sort words)]
    (println "The sorted list of words:")
    (doseq [w sorted-words] (println w))))

Output

The sorted list of words:
apple
blueberry
cherry

linq29: OrderBy - Simple 2

//c#
public void Linq29()
{
    string[] words = { "cherry", "apple", "blueberry" };

    var sortedWords =
        from w in words
        orderby w.Length
        select w;

    Console.WriteLine("The sorted list of words (by length):");
    foreach (var w in sortedWords)
    {
        Console.WriteLine(w);
    }
}
;;clojure
(defn linq29 []
  (let [words ["cherry" "apple" "blueberry"]
        sorted-words (sort-by count words)]
    (println "The sorted list of words (by length):")
    (doseq [w sorted-words] (println w))))

Output

The sorted list of words (by length):
apple
cherry
blueberry

linq30: OrderBy - Simple 3

//c#
public void Linq30()
{
    List<Product> products = GetProductList();

    var sortedProducts =
        from p in products
        orderby p.ProductName
        select p;

    ObjectDumper.Write(sortedProducts);
}
;;clojure
(defn linq30 []
  (let [products products-list
        sorted-products (sort-by :product-name products)]
    (doseq [p sorted-products] (println p))))

Output

#clj_linq.data.Product{:product-id 17, :product-name Alice Mutton, :category Meat/Poultry, :unit-price 39.0, :units-in-stock 0}
#clj_linq.data.Product{:product-id 3, :product-name Aniseed Syrup, :category Condiments, :unit-price 10.0, :units-in-stock 13}
#clj_linq.data.Product{:product-id 40, :product-name Boston Crab Meat, :category Seafood, :unit-price 18.4, :units-in-stock 123}
#clj_linq.data.Product{:product-id 60, :product-name Camembert Pierrot, :category Dairy Products, :unit-price 34.0, :units-in-stock 19}
#clj_linq.data.Product{:product-id 18, :product-name Carnarvon Tigers, :category Seafood, :unit-price 62.5, :units-in-stock 42}
...

linq31: OrderBy - Comparer

//c#
public void Linq31()
{
    string[] words = { "aPPLE", "AbAcUs", "bRaNcH", "BlUeBeRrY", "ClOvEr", "cHeRry" };

    var sortedWords = words.OrderBy(a => a, new CaseInsensitiveComparer());

    ObjectDumper.Write(sortedWords);
}
;;clojure
(defn linq31 []
  (let [words ["aPPLE" "AbAcUs" "bRaNcH" "BlUeBeRrY" "ClOvEr" "cHeRry"]
        sorted-words (sort-by identity case-insensitive-compare words)]
    (doseq [w sorted-words] (println w))))

Output

AbAcUs
aPPLE
BlUeBeRrY
bRaNcH
cHeRry
ClOvEr

linq32: OrderByDescending - Simple 1

//c#
public void Linq32()
{
    double[] doubles = { 1.7, 2.3, 1.9, 4.1, 2.9 };

    var sortedDoubles =
        from d in doubles
        orderby d descending
        select d;

    Console.WriteLine("The doubles from highest to lowest:");
    foreach (var d in sortedDoubles)
    {
        Console.WriteLine(d);
    }
}
;;clojure
(defn linq32 []
  (let [dbls [1.7 2.3 1.9 4.1 2.9]
        sorted-doubles (reverse (sort dbls))]
    (println "The doubles from highest to lowest:")
    (doseq [d sorted-doubles] (println d))))

Output

The doubles from highest to lowest:
4.1
2.9
2.3
1.9
1.7

linq33: OrderByDescending - Simple 2

//c#
public void Linq33()
{
    List<Product> products = GetProductList();

    var sortedProducts =
        from p in products
        orderby p.UnitsInStock descending
        select p;

    ObjectDumper.Write(sortedProducts);
}
;;clojure
(defn linq33 []
  (let [products products-list
        sorted-products (reverse (sort-by :units-in-stock products))]
    (doseq [p sorted-products] (println p))))

Output

#clj_linq.data.Product{:product-id 75, :product-name Rhönbräu Klosterbier, :category Beverages, :unit-price 7.75, :units-in-stock 125}
#clj_linq.data.Product{:product-id 40, :product-name Boston Crab Meat, :category Seafood, :unit-price 18.4, :units-in-stock 123}
#clj_linq.data.Product{:product-id 6, :product-name Grandma's Boysenberry Spread, :category Condiments, :unit-price 25.0, :units-in-stock 120}
#clj_linq.data.Product{:product-id 55, :product-name Pâté chinois, :category Meat/Poultry, :unit-price 24.0, :units-in-stock 115}
#clj_linq.data.Product{:product-id 61, :product-name Sirop d'érable, :category Condiments, :unit-price 28.5, :units-in-stock 113}
...

linq34: OrderByDescending - Comparer

//c#
public void Linq34()
{
    string[] words = { "aPPLE", "AbAcUs", "bRaNcH", "BlUeBeRrY", "ClOvEr", "cHeRry" };

    var sortedWords = words.OrderByDescending(a => a, new CaseInsensitiveComparer());

    ObjectDumper.Write(sortedWords);
}
;;clojure
(defn linq34 []
  (let [words ["aPPLE" "AbAcUs" "bRaNcH" "BlUeBeRrY" "ClOvEr" "cHeRry"]
        sorted-words (->> words
                          (sort-by identity case-insensitive-compare)
                          reverse)]
    (doseq [w sorted-words] (println w))))

Output

ClOvEr
cHeRry
bRaNcH
BlUeBeRrY
aPPLE
AbAcUs

linq35: ThenBy - Simple

//c#
public void Linq35()
{
    string[] digits = { "zero", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine" };

    var sortedDigits =
        from d in digits
        orderby d.Length, d
        select d;

    Console.WriteLine("Sorted digits:");
    foreach (var d in sortedDigits)
    {
        Console.WriteLine(d);
    }
}
;;clojure
(defn linq35 []
  (let [digits ["zero" "one" "two" "three" "four" "five" "six" "seven" "eight" "nine"]
        sorted-digits (order-by [count identity] digits)]
    (println "Sorted digits:")
    (doseq [d sorted-digits] (println d))))

Output

Sorted digits:
one
six
two
five
four
nine
zero
eight
seven
three

linq36: ThenBy - Comparer

//c#
public void Linq36()
{
    string[] words = { "aPPLE", "AbAcUs", "bRaNcH", "BlUeBeRrY", "ClOvEr", "cHeRry" };

    var sortedWords =
        words.OrderBy(a => a.Length)
             .ThenBy(a => a, new CaseInsensitiveComparer());

    ObjectDumper.Write(sortedWords);
}
;;clojure
(defn linq36 []
  (let [words ["aPPLE" "AbAcUs" "bRaNcH" "BlUeBeRrY" "ClOvEr" "cHeRry"]
        sorted-words (order-by [count (fn [x] (.toLowerCase x))] words)]
    (doseq [w sorted-words] (println w))))

Output

aPPLE
AbAcUs
bRaNcH
cHeRry
ClOvEr
BlUeBeRrY

linq37: ThenByDescending - Simple

//c#
public void Linq37()
{
    List<Product> products = GetProductList();

    var sortedProducts =
        from p in products
        orderby p.Category, p.UnitPrice descending
        select p;

    ObjectDumper.Write(sortedProducts);
}
;;clojure
(defn linq37 []
  (let [products products-list
        sorted-products (order-by [:category #(* -1 (:unit-price  %))] products)]
    (doseq [p sorted-products] (println p))))

Output

#clj_linq.data.Product{:product-id 38, :product-name Côte de Blaye, :category Beverages, :unit-price 263.5, :units-in-stock 17}
#clj_linq.data.Product{:product-id 43, :product-name Ipoh Coffee, :category Beverages, :unit-price 46.0, :units-in-stock 17}
#clj_linq.data.Product{:product-id 2, :product-name Chang, :category Beverages, :unit-price 19.0, :units-in-stock 17}
#clj_linq.data.Product{:product-id 1, :product-name Chai, :category Beverages, :unit-price 18.0, :units-in-stock 39}
#clj_linq.data.Product{:product-id 35, :product-name Steeleye Stout, :category Beverages, :unit-price 18.0, :units-in-stock 20}
#clj_linq.data.Product{:product-id 39, :product-name Chartreuse verte, :category Beverages, :unit-price 18.0, :units-in-stock 69}
#clj_linq.data.Product{:product-id 76, :product-name Lakkalikööri, :category Beverages, :unit-price 18.0, :units-in-stock 57}
#clj_linq.data.Product{:product-id 70, :product-name Outback Lager, :category Beverages, :unit-price 15.0, :units-in-stock 15}
#clj_linq.data.Product{:product-id 34, :product-name Sasquatch Ale, :category Beverages, :unit-price 14.0, :units-in-stock 111}
...

linq38: ThenByDescending - Comparer

//c#
public void Linq38()
{
    string[] words = { "aPPLE", "AbAcUs", "bRaNcH", "BlUeBeRrY", "ClOvEr", "cHeRry" };

    var sortedWords =
        words.OrderBy(a => a.Length)
             .ThenByDescending(a => a, new CaseInsensitiveComparer());

    ObjectDumper.Write(sortedWords);
}
;;clojure
(defn linq38 []
  (let [words ["aPPLE" "AbAcUs" "bRaNcH" "BlUeBeRrY" "ClOvEr" "cHeRry"]
        sorted-words (order-by-comparers
                      [#(compare (count %1) (count %2))
                       #(case-insensitive-compare %2 %1)]
                      words)]
    (doseq [w sorted-words] (println w))))

Output

aPPLE
ClOvEr
cHeRry
bRaNcH
AbAcUs
BlUeBeRrY

linq39: Reverse

//c#
public void Linq39()
{
    string[] digits = { "zero", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine" };

    var reversedIDigits = (
        from d in digits
        where d[1] == 'i'
        select d)
        .Reverse();

    Console.WriteLine("A backwards list of the digits with a second character of 'i':");
    foreach (var d in reversedIDigits)
    {
        Console.WriteLine(d);
    }
}
;;clojure
(defn linq39 []
  (let [digits ["zero" "one" "two" "three" "four" "five" "six" "seven" "eight" "nine"]
        sorted-digits (->> digits
                           (filter #(= (get % 1) \i))
                           reverse)]
    (println "A backwards list of the digits with a second character of 'i':")
    (doseq [d sorted-digits] (println d))))

Output

A backwards list of the digits with a second character of 'i':
nine
eight
six
five

LINQ - Grouping Operators

C# utils added

public class AnagramEqualityComparer : IEqualityComparer<string>
{
    public bool Equals(string x, string y)
    {
        return getCanonicalString(x) == getCanonicalString(y);
    }

    public int GetHashCode(string obj)
    {
        return getCanonicalString(obj).GetHashCode();
    }

    private string getCanonicalString(string word)
    {
        char[] wordChars = word.ToCharArray();
        Array.Sort<char>(wordChars);
        return new string(wordChars);
    }
}

Clojure utils added

(defn anagram-comparer [a b] (compare (sort (.toCharArray a)) (sort (.toCharArray b))))

linq40: GroupBy - Simple 1

//c#
public void Linq40()
{
    int[] numbers = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };

    var numberGroups =
        from n in numbers
        group n by n % 5 into g
        select new { Remainder = g.Key, Numbers = g };

    foreach (var g in numberGroups)
    {
        Console.WriteLine("Numbers with a remainder of {0} when divided by 5:", g.Remainder);
        foreach (var n in g.Numbers)
        {
            Console.WriteLine(n);
        }
    }
}
;;clojure
(defn linq40 []
  (let [numbers [5 4 1 3 9 8 6 7 2 0]
        number-groups (for [g (group-by #(mod % 5) numbers)] 
                        {:remainder (first g), :numbers (second g)})]
    (doseq [g number-groups]
      (println "Numbers with a remainder of" (:remainder g) "when divided by 5:")
      (doall (map println (:numbers g))))))

Output

Numbers with a remainder of 0 when divided by 5:
5
0
Numbers with a remainder of 4 when divided by 5:
4
9
Numbers with a remainder of 1 when divided by 5:
1
6
Numbers with a remainder of 3 when divided by 5:
3
8
Numbers with a remainder of 2 when divided by 5:
7
2

linq41: GroupBy - Simple 2

//c#
public void Linq41()
{
    string[] words = { "blueberry", "chimpanzee", "abacus", "banana", "apple", "cheese" };

    var wordGroups =
        from w in words
        group w by w[0] into g
        select new { FirstLetter = g.Key, Words = g };

    foreach (var g in wordGroups)
    {
        Console.WriteLine("Words that start with the letter '{0}':", g.FirstLetter);
        foreach (var w in g.Words)
        {
            Console.WriteLine(w);
        }
    }
}
;;clojure
(defn linq41 []
  (let [words ["blueberry" "chimpanzee" "abacus" "banana" "apple" "cheese"]
        word-groups (for [g (group-by #(first %) words)]
                      {:first-letter (first g), :words (second g)})]
    (doseq [g word-groups]
      (println "Words that start with the letter: " (:first-letter g))
      (doall (map println (:words g))))))

Output

Words that start with the letter:  b
blueberry
banana
Words that start with the letter:  c
chimpanzee
cheese
Words that start with the letter:  a
abacus
apple

linq42: GroupBy - Simple 3

//c#
public void Linq42()
{
    List<Product> products = GetProductList();

    var orderGroups =
        from p in products
        group p by p.Category into g
        select new { Category = g.Key, Products = g };

    ObjectDumper.Write(orderGroups, 1);
}
;;clojure
(defn linq42 []
  (let [products products-list
        order-groups (for [g (group-by #(:category %) products)] 
                       {:category (first g), :products (second g)})]
    (doseq [x order-groups] (println x))))

Output

{:products [#clj_linq.data.Product{:product-id 1, :product-name Chai, :category Beverages, :unit-price 18.0, :units-in-stock 39} #clj_linq.data.Product{:product-id 2, :product-name Chang, :category Beverages, :unit-price 19.0, :units-in-stock 17} #clj_linq.data.Product{:product-id 24, :product-name Guaraná Fantástica, :category Beverages, :unit-price 4.5, :units-in-stock 20} #clj_linq.data.Product{:product-id 34, :product-name Sasquatch Ale, :category Beverages, :unit-price 14.0, :units-in-stock 111} #clj_linq.data.Product{:product-id 35, :product-name Steeleye Stout, :category Beverages, :unit-price 18.0, :units-in-stock 20} #clj_linq.data.Product{:product-id 38, :product-name Côte de Blaye, :category Beverages, :unit-price 263.5, :units-in-stock 17} #clj_linq.data.Product{:product-id 39, :product-name Chartreuse verte, :category Beverages, :unit-price 18.0, :units-in-stock 69} #clj_linq.data.Product{:product-id 43, :product-name Ipoh Coffee, :category Beverages, :unit-price 46.0, :units-in-stock 17} #clj_linq.data.Product{:product-id 67, :product-name Laughing Lumberjack Lager, :category Beverages, :unit-price 14.0, :units-in-stock 52} #clj_linq.data.Product{:product-id 70, :product-name Outback Lager, :category Beverages, :unit-price 15.0, :units-in-stock 15} #clj_linq.data.Product{:product-id 75, :product-name Rhönbräu Klosterbier, :category Beverages, :unit-price 7.75, :units-in-stock 125} #clj_linq.data.Product{:product-id 76, :product-name Lakkalikööri, :category Beverages, :unit-price 18.0, :units-in-stock 57}], :category Beverages}
{:products [#clj_linq.data.Product{:product-id 3, :product-name Aniseed Syrup, :category Condiments, :unit-price 10.0, :units-in-stock 13} #clj_linq.data.Product{:product-id 4, :product-name Chef Anton's Cajun Seasoning, :category Condiments, :unit-price 22.0, :units-in-stock 53} #clj_linq.data.Product{:product-id 5, :product-name Chef Anton's Gumbo Mix, :category Condiments, :unit-price 21.35, :units-in-stock 0} #clj_linq.data.Product{:product-id 6, :product-name Grandma's Boysenberry Spread, :category Condiments, :unit-price 25.0, :units-in-stock 120} #clj_linq.data.Product{:product-id 8, :product-name Northwoods Cranberry Sauce, :category Condiments, :unit-price 40.0, :units-in-stock 6} #clj_linq.data.Product{:product-id 15, :product-name Genen Shouyu, :category Condiments, :unit-price 15.5, :units-in-stock 39} #clj_linq.data.Product{:product-id 44, :product-name Gula Malacca, :category Condiments, :unit-price 19.45, :units-in-stock 27} #clj_linq.data.Product{:product-id 61, :product-name Sirop d'érable, :category Condiments, :unit-price 28.5, :units-in-stock 113} #clj_linq.data.Product{:product-id 63, :product-name Vegie-spread, :category Condiments, :unit-price 43.9, :units-in-stock 24} #clj_linq.data.Product{:product-id 65, :product-name Louisiana Fiery Hot Pepper Sauce, :category Condiments, :unit-price 21.05, :units-in-stock 76} #clj_linq.data.Product{:product-id 66, :product-name Louisiana Hot Spiced Okra, :category Condiments, :unit-price 17.0, :units-in-stock 4} #clj_linq.data.Product{:product-id 77, :product-name Original Frankfurter grüne Soße, :category Condiments, :unit-price 13.0, :units-in-stock 32}], :category Condiments}

linq43: GroupBy - Nested

//c#
public void Linq43()
{
    List<Customer> customers = GetCustomerList();

    var customerOrderGroups =
        from c in customers
        select
            new
            {
                c.CompanyName,
                YearGroups =
                    from o in c.Orders
                    group o by o.OrderDate.Year into yg
                    select
                        new
                        {
                            Year = yg.Key,
                            MonthGroups =
                                from o in yg
                                group o by o.OrderDate.Month into mg
                                select new { Month = mg.Key, Orders = mg }
                        }
            };

    ObjectDumper.Write(customerOrderGroups, 3);
}
;;clojure
(defn linq43 []
  (let [customers customers-list
        customer-order-groups
        (for [c customers] 
          {:company-name (:company-name c),
           :year-groups
           (for [yg (group-by #(time/year (:order-date %)) (:orders c))]
             {:year (first yg)
              :month-groups
              (for [mg (group-by #(:order-date %) (second yg))]                 
                {:month (time/month (first mg)), :orders (second mg)})})})]
    (doseq [x customer-order-groups] (println x))))

Output

{:company-name Alfreds Futterkiste, :year-groups ({:month-groups ({:month 8, :orders [#clj_linq.data.Order{:order-id 10643, :order-date #<DateTime 1997-08-25T00:00:00.000-04:00>, :total 814.50M}]} {:month 10, :orders [#clj_linq.data.Order{:order-id 10692, :order-date #<DateTime 1997-10-03T00:00:00.000-04:00>, :total 878.00M}]} {:month 10, :orders [#clj_linq.data.Order{:order-id 10702, :order-date #<DateTime 1997-10-13T00:00:00.000-04:00>, :total 330.00M}]} {:month 1, :orders [#clj_linq.data.Order{:order-id 10835, :order-date #<DateTime 1998-01-15T00:00:00.000-05:00>, :total 845.80M}]} {:month 3, :orders [#clj_linq.data.Order{:order-id 10952, :order-date #<DateTime 1998-03-16T00:00:00.000-05:00>, :total 471.20M}]} {:month 4, :orders [#clj_linq.data.Order{:order-id 11011, :order-date #<DateTime 1998-04-09T00:00:00.000-04:00>, :total 933.50M}]}), :year nil})}

linq44: GroupBy - Comparer

//c#
public void Linq44()
{
    string[] anagrams = { "from   ", " salt", " earn ", "  last   ", " near ", " form  " };

    var orderGroups = anagrams.GroupBy(w => w.Trim(), new AnagramEqualityComparer());

    ObjectDumper.Write(orderGroups, 1);
}
;;clojure
(defn linq44 []
  (let [anagrams ["from   " " salt" " earn " "  last   " " near " " form  "]
        order-groups (group-by #(sort (.toCharArray (.trim %))) anagrams)]
    (doseq [x order-groups] (println (second x)))))

Output

[from     form  ]
[ salt   last   ]
[ earn   near ]

linq45: GroupBy - Comparer, Mapped

//c#
public void Linq45()
{
    string[] anagrams = { "from   ", " salt", " earn ", "  last   ", " near ", " form  " };

    var orderGroups = anagrams.GroupBy(
                w => w.Trim(),
                a => a.ToUpper(),
                new AnagramEqualityComparer()
                );

    ObjectDumper.Write(orderGroups, 1);
}
;;clojure
(defn linq45 []
  (let [anagrams ["from   " " salt" " earn " "  last   " " near " " form  "]
        order-groups (group-by #(sort (.toCharArray (.trim %))) 
                               (map #(.toUpperCase %) anagrams))]
    (doseq [x order-groups] (println (second x)))))

Output

[FROM     FORM  ]
[ SALT   LAST   ]
[ EARN   NEAR ]

LINQ - Set Operators

linq46: Distinct - 1

//c#
public void Linq46()
{
    int[] factorsOf300 = { 2, 2, 3, 5, 5 };

    var uniqueFactors = factorsOf300.Distinct();

    Console.WriteLine("Prime factors of 300:");
    foreach (var f in uniqueFactors)
    {
        Console.WriteLine(f);
    }
}
;;clojure
(defn linq46 []
  (let [factors-of-300 [2, 2, 3, 5, 5]
        unique-factors (distinct factors-of-300)]
    (println "Prime factors of 300:")
    (doseq [n unique-factors] (println n))))

Output

Prime factors of 300:
2
3
5

linq47: Distinct - 2

//c#
public void Linq47()
{
    List<Product> products = GetProductList();

    var categoryNames = (
        from p in products
        select p.Category)
        .Distinct();

    Console.WriteLine("Category names:");
    foreach (var n in categoryNames)
    {
        Console.WriteLine(n);
    }
}
;;clojure
(defn linq47 []
  (let [products products-list
        category-names (->> products
                            (map :category)
                            distinct)]
    (println "Category names:")
    (doseq [c category-names] (println c))))

Output

Category names:
Beverages
Condiments
Produce
Meat/Poultry
Seafood
Dairy Products
Confections
Grains/Cereals

linq48: Union - 1

//c#
public void Linq48()
{
    int[] numbersA = { 0, 2, 4, 5, 6, 8, 9 };
    int[] numbersB = { 1, 3, 5, 7, 8 };

    var uniqueNumbers = numbersA.Union(numbersB);

    Console.WriteLine("Unique numbers from both arrays:");
    foreach (var n in uniqueNumbers)
    {
        Console.WriteLine(n);
    }
}
;;clojure
(defn linq48 []
  (let [numbers-a [0 2 4 5 6 8 9]
        numbers-b [1 3 5 7 8]
        unique-numbers (union (set numbers-a) (set numbers-b))]
    (println "Unique numbers from both arrays:")
    (doseq [n unique-numbers] (println n))))

Output

Unique numbers from both arrays:
0
1
2
3
4
5
6
7
8
9

linq49: Union - 2

//c#
public void Linq49()
{
    List<Product> products = GetProductList();
    List<Customer> customers = GetCustomerList();

    var productFirstChars =
        from p in products
        select p.ProductName[0];
    var customerFirstChars =
        from c in customers
        select c.CompanyName[0];

    var uniqueFirstChars = productFirstChars.Union(customerFirstChars);

    Console.WriteLine("Unique first letters from Product names and Customer names:");
    foreach (var ch in uniqueFirstChars)
    {
        Console.WriteLine(ch);
    }
}
;;clojure
(defn linq49 []
  (let [products products-list
        customers customers-list
        product-first-chars (map #(first (:product-name %)) products)
        customer-first-chars (map #(first (:company-name %)) customers)
        unique-first-chars (union (set product-first-chars) (set customer-first-chars))]
    (println "Unique first letters from Product names and Customer names:")
    (doseq [x unique-first-chars] (println x))))

Output

Unique first letters from Product names and Customer names:
A
B
C
D
E
F
G
H
I
J
K
L
M
N
O
P
Q
R
S
T
U
V
W
Z

linq50: Intersect - 1

//c#
public void Linq50()
{
    int[] numbersA = { 0, 2, 4, 5, 6, 8, 9 };
    int[] numbersB = { 1, 3, 5, 7, 8 };

    var commonNumbers = numbersA.Intersect(numbersB);

    Console.WriteLine("Common numbers shared by both arrays:");
    foreach (var n in commonNumbers)
    {
        Console.WriteLine(n);
    }
}
;;clojure
(defn linq50 []
  (let [numbers-a [0 2 4 5 6 8 9]
        numbers-b [1 3 5 7 8]
        common-numbers (intersection (set numbers-a) (set numbers-b))]
    (println "Common numbers shared by both arrays:")
    (doseq [n common-numbers] (println n))))

Output

Common numbers shared by both arrays:
5
8

linq51: Intersect - 2

//c#
public void Linq51()
{
    List<Product> products = GetProductList();
    List<Customer> customers = GetCustomerList();

    var productFirstChars =
        from p in products
        select p.ProductName[0];
    var customerFirstChars =
        from c in customers
        select c.CompanyName[0];

    var commonFirstChars = productFirstChars.Intersect(customerFirstChars);

    Console.WriteLine("Common first letters from Product names and Customer names:");
    foreach (var ch in commonFirstChars)
    {
        Console.WriteLine(ch);
    }
}
;;clojure
(defn linq51 []
  (let [products products-list
        customers customers-list
        product-first-chars (map #(first (:product-name %)) products)
        customer-first-chars (map #(first (:company-name %)) customers)
        common-first-chars (intersection (set product-first-chars) (set customer-first-chars))]
    (println "Common first letters from Product names and Customer names:")
    (doseq [x common-first-chars] (println x))))

Output

Common first letters from Product names and Customer names:
A
B
C
E
F
G
I
K
L
M
N
O
P
Q
R
S
T
V
W

linq52: Except - 1

//c#
public void Linq52()
{
    int[] numbersA = { 0, 2, 4, 5, 6, 8, 9 };
    int[] numbersB = { 1, 3, 5, 7, 8 };

    IEnumerable<int> aOnlyNumbers = numbersA.Except(numbersB);

    Console.WriteLine("Numbers in first array but not second array:");
    foreach (var n in aOnlyNumbers)
    {
        Console.WriteLine(n);
    }
}
;;clojure
(defn linq52 []
  (let [numbers-a [0 2 4 5 6 8 9]
        numbers-b [1 3 5 7 8]
        a-only-numbers (difference (set numbers-a) (set numbers-b))]
  (println "Numbers in first array but not second array:")
  (doseq [n a-only-numbers] (println n))))

Output

Numbers in first array but not second array:
0
2
4
6
9

linq53: Except - 2

//c#
public void Linq53()
{
    List<Product> products = GetProductList();
    List<Customer> customers = GetCustomerList();

    var productFirstChars =
        from p in products
        select p.ProductName[0];
    var customerFirstChars =
        from c in customers
        select c.CompanyName[0];

    var productOnlyFirstChars = productFirstChars.Except(customerFirstChars);

    Console.WriteLine("First letters from Product names, but not from Customer names:");
    foreach (var ch in productOnlyFirstChars)
    {
        Console.WriteLine(ch);
    }
}
;;clojure
(defn linq53 []
  (let [products products-list
        customers customers-list
        product-first-chars (map #(first (:product-name %)) products)
        customer-first-chars (map #(first (:company-name %)) customers)
        product-only-first-chars (difference (set product-first-chars) 
                                             (set customer-first-chars))]
    (println "First letters from Product names, but not from Customer names:")
    (doseq [x  product-only-first-chars] (println x))))

Output

First letters from Product names, but not from Customer names:
J
U
Z

LINQ - Conversion Operators

linq54: ToArray

//c#
public void Linq54()
{
    double[] doubles = { 1.7, 2.3, 1.9, 4.1, 2.9 };

    var sortedDoubles =
        from d in doubles
        orderby d descending
        select d;
    var doublesArray = sortedDoubles.ToArray();

    Console.WriteLine("Every other double from highest to lowest:");
    for (int d = 0; d < doublesArray.Length; d += 2)
    {
        Console.WriteLine(doublesArray[d]);
    }
}
;;clojure
(defn linq54 []
  (let [dbls [1.7 2.3 1.9 4.1 2.9]
        sorted-doubles (->> dbls sort reverse)]
    (println "Every other double from highest to lowest:")
    (doseq [d (take-nth 2 sorted-doubles)] (println d))))

Output

Every other double from highest to lowest:
4.1
2.3
1.7

linq55: ToList

//c#
public void Linq55()
{
    string[] words = { "cherry", "apple", "blueberry" };

    var sortedWords =
        from w in words
        orderby w
        select w;
    var wordList = sortedWords.ToList();

    Console.WriteLine("The sorted word list:");
    foreach (var w in wordList)
    {
        Console.WriteLine(w);
    }
}
;;clojure
(defn linq55 []
  (let [words ["cherry", "apple", "blueberry"]
        sorted-words (->> words
                          sort
                          (apply list))]
    (println "The sorted word list:")
    (doseq [w sorted-words] (println w))))

Output

The sorted word list:
apple
blueberry
cherry

linq56: ToDictionary

//c#
public void Linq56()
{
    var scoreRecords = new[] { new {Name = "Alice", Score = 50},
                                new {Name = "Bob"  , Score = 40},
                                new {Name = "Cathy", Score = 45}
                            };

    var scoreRecordsDict = scoreRecords.ToDictionary(sr => sr.Name);

    Console.WriteLine("Bob's score: {0}", scoreRecordsDict["Bob"]);
}
;;clojure
(defn linq56 []
  (let [sorted-records [{:name "Alice", :score 50}
                        {:name "Bob", :score 40}
                        {:name "Cathy", :score 45}]
        sorted-records-dict (->> sorted-records
                                 (map #(hash-map (:name %) (:score %)))
                                 (into {}))]
    (println "Bob's score:" (sorted-records-dict "Bob"))))

Output

Bob's score: 40

linq57: OfType

//c#
public void Linq57()
{
    object[] numbers = { null, 1.0, "two", 3, "four", 5, "six", 7.0 };

    var doubles = numbers.OfType<double>();

    Console.WriteLine("Numbers stored as doubles:");
    foreach (var d in doubles)
    {
        Console.WriteLine(d);
    }
}
;;clojure
(defn linq57 []
  (let [numbers [nil 1.0 "two" 3 "four" 5 "six" 7.0]
        dbls (filter #(= (type %) java.lang.Double) numbers)]
    (println "Numbers stored as doubles:")
    (doseq [d dbls] (println d))))

Output

Numbers stored as doubles:
1.0
7.0

LINQ - Element Operators

linq58: First - Simple

//c#
public void Linq58()
{
    List<Product> products = GetProductList();

    Product product12 = (
        from p in products
        where p.ProductID == 12
        select p)
        .First();

    ObjectDumper.Write(product12);
}
;;clojure
(defn linq58 []
  (let [products products-list
        product-12 (->> products
                        (filter #(= (:product-id %) 12))
                        first)]
    (println product-12)))

Output

#clj_linq.data.Product{:product-id 12, :product-name Queso Manchego La Pastora, :category Dairy Products, :unit-price 38.0, :units-in-stock 86}

linq59: First - Condition

//c#
public void Linq59()
{
    string[] strings = { "zero", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine" };

    string startsWithO = strings.First(s => s[0] == 'o');

    Console.WriteLine("A string starting with 'o': {0}", startsWithO);
}
;;clojure
(defn linq59 []
  (let [strings ["zero", "one", "two", "three", "four", 
                 "five", "six", "seven", "eight", "nine"]
        starts-with-o (first (filter #(= (first %) \o) strings))]
    (println "A string starting with 'o':" starts-with-o)))

Output

A string starting with 'o': one

linq61: FirstOrDefault - Simple

//c#
public void Linq61()
{
    int[] numbers = { };

    int firstNumOrDefault = numbers.FirstOrDefault();

    Console.WriteLine(firstNumOrDefault);
}
;;clojure
(defn linq61 []
  (let [numbers []
        first-num-or-default (get numbers 0 0)]
    (println first-num-or-default)))

Output

0

linq62: FirstOrDefault - Condition

//c#
public void Linq62()
{
    List<Product> products = GetProductList();

    Product product789 = products.FirstOrDefault(p => p.ProductID == 789);

    Console.WriteLine("Product 789 exists: {0}", product789 != null);
}
;;clojure
(defn linq62 []
  (let [products products-list
        product-789 (->> products
                         (filter #(= (:product-id %) 789))
                         first)]
    (println "Product 789 exists:" (not= product-789 nil))))

Output

Product 789 exists: false

linq64: ElementAt

//c#
public void Linq64()
{
    int[] numbers = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };

    int fourthLowNum = (
        from n in numbers
        where n > 5
        select n)
        .ElementAt(1);  // second number is index 1 because sequences use 0-based indexing

    Console.WriteLine("Second number > 5: {0}", fourthLowNum);
}
;;clojure
(defn linq64 []
  (let [numbers [5 4 1 3 9 8 6 7 2 0]
        fourth-low-num (->> numbers
                            (filter #(> % 5))
                            second)]
    (println "Second number > 5:" fourth-low-num)))

Output

Second number > 5: 8

LINQ - Generation Operators

linq65: Range

//c#
public void Linq65()
{
    var numbers =
        from n in Enumerable.Range(100, 50)

        select new { Number = n, OddEven = n % 2 == 1 ? "odd" : "even" };

    foreach (var n in numbers)
    {
        Console.WriteLine("The number {0} is {1}.", n.Number, n.OddEven);
    }
}
;;clojure
(defn linq65 []
  (let [numbers (for [n (range 100 151)] 
                  {:number n,
                   :odd-even (if (= (mod n 2) 1) "odd" "even")})]
    (doseq [n numbers] (println "The number" (:number n) "is" (:odd-even n)))))

Output

The number 100 is even
The number 101 is odd
The number 102 is even
The number 103 is odd
The number 104 is even
The number 105 is odd
The number 106 is even
The number 107 is odd
The number 108 is even
The number 109 is odd
The number 110 is even
...

linq66: Repeat

//c#
public void Linq66()
{
    var numbers = Enumerable.Repeat(7, 10);

    foreach (var n in numbers)
    {
        Console.WriteLine(n);
    }
}
;;clojure
(defn linq66 []
  (let [numbers (repeat 10 7)]
    (doseq [n numbers] (println n))))

Output

7
7
7
7
7
7
7
7
7
7

LINQ - Quantifiers

linq67: Any - Simple

//c#
public void Linq67()
{
    string[] words = { "believe", "relief", "receipt", "field" };

    bool iAfterE = words.Any(w => w.Contains("ei"));

    Console.WriteLine("There is a word that contains in the list that contains 'ei': {0}", iAfterE);
}
;;clojure
(defn linq67 []
  (let [words ["believe" "relief" "receipt" "field"]
        i-after-e (some #(.contains % "ie") words)]
    (println "There is a word that contains in the list that contains 'ei':" i-after-e)))

Output

There is a word that contains in the list that contains 'ei': true

linq69: Any - Grouped

//c#
public void Linq69()
{
    List<Product> products = GetProductList();
    var productGroups =
        from p in products
        group p by p.Category into g
        where g.Any(p => p.UnitsInStock == 0)
        select new { Category = g.Key, Products = g };

    ObjectDumper.Write(productGroups, 1);
}
;;clojure
(defn linq69 []
  (let [products products-list
        product-groups
        (->> products
             (group-by :category)
             (filter #(some (fn [p] (= (:units-in-stock p) 0)) (get % 1)))
             (map #(identity {:category (first %), :products (second %)})))]
    (doseq [x product-groups] (println x))))

Output

{:category Condiments, :products [#clj_linq.data.Product{:product-id 3, :product-name Aniseed Syrup, :category Condiments, :unit-price 10.0, :units-in-stock 13} #clj_linq.data.Product{:product-id 4, :product-name Chef Anton's Cajun Seasoning, :category Condiments, :unit-price 22.0, :units-in-stock 53} #clj_linq.data.Product{:product-id 5, :product-name Chef Anton's Gumbo Mix, :category Condiments, :unit-price 21.35, :units-in-stock 0} #clj_linq.data.Product{:product-id 6, :product-name Grandma's Boysenberry Spread, :category Condiments, :unit-price 25.0, :units-in-stock 120} #clj_linq.data.Product{:product-id 8, :product-name Northwoods Cranberry Sauce, :category Condiments, :unit-price 40.0, :units-in-stock 6} #clj_linq.data.Product{:product-id 15, :product-name Genen Shouyu, :category Condiments, :unit-price 15.5, :units-in-stock 39} #clj_linq.data.Product{:product-id 44, :product-name Gula Malacca, :category Condiments, :unit-price 19.45, :units-in-stock 27} #clj_linq.data.Product{:product-id 61, :product-name Sirop d'érable, :category Condiments, :unit-price 28.5, :units-in-stock 113} #clj_linq.data.Product{:product-id 63, :product-name Vegie-spread, :category Condiments, :unit-price 43.9, :units-in-stock 24} #clj_linq.data.Product{:product-id 65, :product-name Louisiana Fiery Hot Pepper Sauce, :category Condiments, :unit-price 21.05, :units-in-stock 76} #clj_linq.data.Product{:product-id 66, :product-name Louisiana Hot Spiced Okra, :category Condiments, :unit-price 17.0, :units-in-stock 4} #clj_linq.data.Product{:product-id 77, :product-name Original Frankfurter grüne Soße, :category Condiments, :unit-price 13.0, :units-in-stock 32}]}
...

linq70: All - Simple

//c#
public void Linq70()
{
    int[] numbers = { 1, 11, 3, 19, 41, 65, 19 };

    bool onlyOdd = numbers.All(n => n % 2 == 1);

    Console.WriteLine("The list contains only odd numbers: {0}", onlyOdd);
}
;;clojure
(defn linq70 []
  (let [numbers [1 11 3 19 41 65 19]
        only-odd (every? #(= (mod % 2) 1) numbers)]
    (println "The list contains only odd numbers:" only-odd)))

Output

The list contains only odd numbers: true

linq72: All - Grouped

//c#
public void Linq72()
{
    List<Product> products = GetProductList();

    var productGroups =
        from p in products
        group p by p.Category into g
        where g.All(p => p.UnitsInStock > 0)
        select new { Category = g.Key, Products = g };

    ObjectDumper.Write(productGroups, 1);
}
;;clojure
(defn linq72 []
  (let [products products-list
        product-groups
        (->> products
             (group-by :category)
             (filter #(every? (fn [p] (> (:units-in-stock p) 0)) (second %)))
             (map #(identity {:category (first %), :products (second %)})))]
    (doseq [x product-groups] (println x))))

Output

{:category Beverages, :products [#clj_linq.data.Product{:product-id 1, :product-name Chai, :category Beverages, :unit-price 18.0, :units-in-stock 39} #clj_linq.data.Product{:product-id 2, :product-name Chang, :category Beverages, :unit-price 19.0, :units-in-stock 17} #clj_linq.data.Product{:product-id 24, :product-name Guaraná Fantástica, :category Beverages, :unit-price 4.5, :units-in-stock 20} #clj_linq.data.Product{:product-id 34, :product-name Sasquatch Ale, :category Beverages, :unit-price 14.0, :units-in-stock 111} #clj_linq.data.Product{:product-id 35, :product-name Steeleye Stout, :category Beverages, :unit-price 18.0, :units-in-stock 20} #clj_linq.data.Product{:product-id 38, :product-name Côte de Blaye, :category Beverages, :unit-price 263.5, :units-in-stock 17} #clj_linq.data.Product{:product-id 39, :product-name Chartreuse verte, :category Beverages, :unit-price 18.0, :units-in-stock 69} #clj_linq.data.Product{:product-id 43, :product-name Ipoh Coffee, :category Beverages, :unit-price 46.0, :units-in-stock 17} #clj_linq.data.Product{:product-id 67, :product-name Laughing Lumberjack Lager, :category Beverages, :unit-price 14.0, :units-in-stock 52} #clj_linq.data.Product{:product-id 70, :product-name Outback Lager, :category Beverages, :unit-price 15.0, :units-in-stock 15} #clj_linq.data.Product{:product-id 75, :product-name Rhönbräu Klosterbier, :category Beverages, :unit-price 7.75, :units-in-stock 125} #clj_linq.data.Product{:product-id 76, :product-name Lakkalikööri, :category Beverages, :unit-price 18.0, :units-in-stock 57}]}
...

LINQ - Aggregate Operators

Clojure utils added

(defn average [coll] (/ (reduce + coll) (count coll)))

linq73: Count - Simple

//c#
public void Linq73()
{
    int[] factorsOf300 = { 2, 2, 3, 5, 5 };

    int uniqueFactors = factorsOf300.Distinct().Count();

    Console.WriteLine("There are {0} unique factors of 300.", uniqueFactors);
}
;;clojure
(defn linq73 []
  (let [factors-of-300 [2 2 3 5 5]
        unique-factors (count (distinct factors-of-300))]    
    (println "There are" unique-factors "unique factors of 300.")))

Output

There are 3 unique factors of 300.

linq74: Count - Conditional

//c#
public void Linq74()
{
    int[] numbers = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };

    int oddNumbers = numbers.Count(n => n % 2 == 1);

    Console.WriteLine("There are {0} odd numbers in the list.", oddNumbers);
}
;;clojure
(defn linq74 []
  (let [numbers [4 5 1 3 9 0 6 7 2 0]
        odd-numbers (count (for [n numbers :when (= 1 (mod n 2))] n))]
    (println "There are" odd-numbers "odd numbers in the list.")))

Output

There are 5 odd numbers in the list.

linq76: Count - Nested

//c#
public void Linq76()
{
    List<Customer> customers = GetCustomerList();

    var orderCounts =
        from c in customers
        select new { c.CustomerID, OrderCount = c.Orders.Count() };

    ObjectDumper.Write(orderCounts);
}
;;clojure
(defn linq76 []
  (let [customers customers-list
        order-counts 
        (for [c customers]
          {:customer-id (:customer-id c) :order-count (count (:orders c))})]
  (doseq [x order-counts] (println x))))

Output

{:customer-id ALFKI, :order-count 6}
{:customer-id ANATR, :order-count 4}
{:customer-id ANTON, :order-count 7}
{:customer-id AROUT, :order-count 13}
{:customer-id BERGS, :order-count 18}
{:customer-id BLAUS, :order-count 7}
{:customer-id BLONP, :order-count 11}
...

linq77: Count - Grouped

//c#
public void Linq77()
{
    List<Product> products = GetProductList();

    var categoryCounts =
        from p in products
        group p by p.Category into g
        select new { Category = g.Key, ProductCount = g.Count() };

    ObjectDumper.Write(categoryCounts
}
;;clojure
(defn linq77 []
  (let [products products-list
        category-counts
        (->> products
             (group-by :category)
             (map #(identity {:category (first %),
                              :product-count (count (second %))})))]
    (doseq [x category-counts] (println x))))

Output

{:category Beverages, :product-count 12}
{:category Condiments, :product-count 12}
{:category Produce, :product-count 5}
{:category Meat/Poultry, :product-count 6}
{:category Seafood, :product-count 12}
{:category Dairy Products, :product-count 10}
{:category Confections, :product-count 13}
{:category Grains/Cereals, :product-count 7}

linq78: Sum - Simple

//c#
public void Linq78()
{
    int[] numbers = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };

    double numSum = numbers.Sum();

    Console.WriteLine("The sum of the numbers is {0}.", numSum);
}
;;clojure
(defn linq78 []
  (let [numbers [5 4 1 3 9 8 6 7 2 0]
        num-sum (reduce + numbers)]
    (println "The sum of the numbers is " num-sum)))

Output

The sum of the numbers is  45

linq79: Sum - Projection

//c#
public void Linq79()
{
    string[] words = { "cherry", "apple", "blueberry" };

    double totalChars = words.Sum(w => w.Length);

    Console.WriteLine("There are a total of {0} characters in these words.", totalChars);
}
;;clojure
(defn linq79 []
  (let [words ["cherry", "apple", "blueberry"]
        total-chars (reduce + (map count words))]
    (println "There are a total of" total-chars "characters in these words.")))

Output

There are a total of 20 characters in these words.

linq80: Sum - Grouped

//c#
public void Linq80()
{
    List<Product> products = GetProductList();

    var categories =
        from p in products
        group p by p.Category into g
        select new { Category = g.Key, TotalUnitsInStock = g.Sum(p => p.UnitsInStock) };

    ObjectDumper.Write(categories);
}
;;clojure
(defn linq80 []
  (let [products products-list
        categories
        (->> products
             (group-by :category)
             (map #(identity 
                    {:category (get % 0),
                     :total-units-in-stock (reduce + (map :units-in-stock (get % 1)))})))]
    (doseq [x categories] (println x))))

Output

{:category Beverages, :total-units-in-stock 559}
{:category Condiments, :total-units-in-stock 507}
{:category Produce, :total-units-in-stock 100}
{:category Meat/Poultry, :total-units-in-stock 165}
{:category Seafood, :total-units-in-stock 701}
{:category Dairy Products, :total-units-in-stock 393}
{:category Confections, :total-units-in-stock 386}
{:category Grains/Cereals, :total-units-in-stock 308}

linq81: Min - Simple

//c#
public void Linq81()
{
    int[] numbers = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };

    int minNum = numbers.Min();

    Console.WriteLine("The minimum number is {0}.", minNum);
}
;;clojure
(defn linq81 []
  (let [numbers [5 4 1 3 9 8 6 7 2 0]
        min-num (apply min numbers)]
    (println "The minimum number is" min-num)))

Output

The minimum number is 0

linq82: Min - Projection

//c#
public void Linq82()
{
    string[] words = { "cherry", "apple", "blueberry" };

    int shortestWord = words.Min(w => w.Length);

    Console.WriteLine("The shortest word is {0} characters long.", shortestWord);
}
;;clojure
(defn linq82 []
  (let [words ["cherry", "apple", "blueberry"]
        shortest-word (apply min (map count words))]
    (println "The shortest word is" shortest-word "characters long.")))

Output

The shortest word is 5 characters long.

linq83: Min - Grouped

//c#
public void Linq83()
{
    List<Product> products = GetProductList();

    var categories =
        from p in products
        group p by p.Category into g
        select new { Category = g.Key, CheapestPrice = g.Min(p => p.UnitPrice) };

    ObjectDumper.Write(categories);
}
;;clojure
(defn linq83 []
  (let [products products-list
        categories
        (->> products
             (group-by :category)
             (map #(identity {:category (first %),
                             :cheapest-price (apply min (map :unit-price (second %)))})))]
    (doseq [c categories] (println c))))

Output

{:category Beverages, :cheapest-price 4.5}
{:category Condiments, :cheapest-price 10.0}
{:category Produce, :cheapest-price 10.0}
{:category Meat/Poultry, :cheapest-price 7.45}
{:category Seafood, :cheapest-price 6.0}
{:category Dairy Products, :cheapest-price 2.5}
{:category Confections, :cheapest-price 9.2}
{:category Grains/Cereals, :cheapest-price 7.0}

linq84: Min - Elements

//c#
public void Linq84()
{
    List<Product> products = GetProductList();

    var categories =
        from p in products
        group p by p.Category into g
        let minPrice = g.Min(p => p.UnitPrice)
        select new { Category = g.Key, CheapestProducts = g.Where(p => p.UnitPrice == minPrice) };

    ObjectDumper.Write(categories, 1);
}
;;clojure
(defn linq84 []
  (let [products products-list
        categories
        (for [g (group-by :category products)
              :let [min-price (apply min (map :unit-price (second g)))]]
          {:category (first g)
           :cheapest-products (for [p (second g) 
                                    :when (= (:unit-price p) min-price)] p)})]
    (doseq [c categories] (println c))))

Output

{:category Beverages, :cheapest-products (#clj_linq.data.Product{:product-id 24, :product-name Guaraná Fantástica, :category Beverages, :unit-price 4.5, :units-in-stock 20})}
{:category Condiments, :cheapest-products (#clj_linq.data.Product{:product-id 3, :product-name Aniseed Syrup, :category Condiments, :unit-price 10.0, :units-in-stock 13})}
{:category Produce, :cheapest-products (#clj_linq.data.Product{:product-id 74, :product-name Longlife Tofu, :category Produce, :unit-price 10.0, :units-in-stock 4})}
{:category Meat/Poultry, :cheapest-products (#clj_linq.data.Product{:product-id 54, :product-name Tourtière, :category Meat/Poultry, :unit-price 7.45, :units-in-stock 21})}
{:category Seafood, :cheapest-products (#clj_linq.data.Product{:product-id 13, :product-name Konbu, :category Seafood, :unit-price 6.0, :units-in-stock 24})}
{:category Dairy Products, :cheapest-products (#clj_linq.data.Product{:product-id 33, :product-name Geitost, :category Dairy Products, :unit-price 2.5, :units-in-stock 112})}
{:category Confections, :cheapest-products (#clj_linq.data.Product{:product-id 19, :product-name Teatime Chocolate Biscuits, :category Confections, :unit-price 9.2, :units-in-stock 25})}
{:category Grains/Cereals, :cheapest-products (#clj_linq.data.Product{:product-id 52, :product-name Filo Mix, :category Grains/Cereals, :unit-price 7.0, :units-in-stock 38})}

linq85: Max - Simple

//c#
public void Linq85()
{
    int[] numbers = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };

    int maxNum = numbers.Max();

    Console.WriteLine("The maximum number is {0}.", maxNum);
}
;;clojure
(defn linq85 []
  (let [numbers [5 4 1 3 9 8 6 7 2 0]
        max-num (apply max numbers)]
    (println "The maximum number is" max-num)))

Output

The maximum number is 9

linq86: Max - Projection

//c#
public void Linq86()
{
    string[] words = { "cherry", "apple", "blueberry" };

    int longestLength = words.Max(w => w.Length);

    Console.WriteLine("The longest word is {0} characters long.", longestLength);
}
;;clojure
(defn linq86 []
  (let [words ["cherry", "apple", "blueberry"]
        longest-word (apply max (map count words))]
    (println "The longest word is" longest-word "characters long.")))

Output

The longest word is 9 characters long.

linq87: Max - Grouped

//c#
public void Linq87()
{
    List<Product> products = GetProductList();

    var categories =
        from p in products
        group p by p.Category into g
        select new { Category = g.Key, MostExpensivePrice = g.Max(p => p.UnitPrice) };

    ObjectDumper.Write(categories);
}
;;clojure
(defn linq87 []
  (let [products products-list
        categories
        (->> products
             (group-by :category)
             (map #(identity 
                    {:category (get % 0),
                     :most-expensive-price (apply max (map :unit-price (get % 1)))})))]
    (doseq [c categories] (println c))))

Output

{:category Beverages, :most-expensive-price 263.5}
{:category Condiments, :most-expensive-price 43.9}
{:category Produce, :most-expensive-price 53.0}
{:category Meat/Poultry, :most-expensive-price 123.79}
{:category Seafood, :most-expensive-price 62.5}
{:category Dairy Products, :most-expensive-price 55.0}
{:category Confections, :most-expensive-price 81.0}
{:category Grains/Cereals, :most-expensive-price 38.0}

linq88: Max - Elements

//c#
public void Linq88()
{
    List<Product> products = GetProductList();

    var categories =
        from p in products
        group p by p.Category into g
        let maxPrice = g.Max(p => p.UnitPrice)
        select new { Category = g.Key, MostExpensiveProducts = g.Where(p => p.UnitPrice == maxPrice) };

    ObjectDumper.Write(categories, 1);
}
;;clojure
(defn linq88 []
  (let [products products-list
        categories
        (for [g (group-by :category products)
              :let [max-price (apply max (map :unit-price (second g)))]]
          {:category (first g)
           :most-expensive-products
           (for [p (second g) :when (= (:unit-price p) max-price)] p)})]
    (doseq [c categories] (println c))))

Output

{:category Beverages, :most-expensive-products (#clj_linq.data.Product{:product-id 38, :product-name Côte de Blaye, :category Beverages, :unit-price 263.5, :units-in-stock 17})}
{:category Condiments, :most-expensive-products (#clj_linq.data.Product{:product-id 63, :product-name Vegie-spread, :category Condiments, :unit-price 43.9, :units-in-stock 24})}
{:category Produce, :most-expensive-products (#clj_linq.data.Product{:product-id 51, :product-name Manjimup Dried Apples, :category Produce, :unit-price 53.0, :units-in-stock 20})}
{:category Meat/Poultry, :most-expensive-products (#clj_linq.data.Product{:product-id 29, :product-name Thüringer Rostbratwurst, :category Meat/Poultry, :unit-price 123.79, :units-in-stock 0})}
{:category Seafood, :most-expensive-products (#clj_linq.data.Product{:product-id 18, :product-name Carnarvon Tigers, :category Seafood, :unit-price 62.5, :units-in-stock 42})}
{:category Dairy Products, :most-expensive-products (#clj_linq.data.Product{:product-id 59, :product-name Raclette Courdavault, :category Dairy Products, :unit-price 55.0, :units-in-stock 79})}
{:category Confections, :most-expensive-products (#clj_linq.data.Product{:product-id 20, :product-name Sir Rodney's Marmalade, :category Confections, :unit-price 81.0, :units-in-stock 40})}
{:category Grains/Cereals, :most-expensive-products (#clj_linq.data.Product{:product-id 56, :product-name Gnocchi di nonna Alice, :category Grains/Cereals, :unit-price 38.0, :units-in-stock 21})}

linq89: Average - Simple

//c#
public void Linq89()
{
    int[] numbers = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };

    double averageNum = numbers.Average();

    Console.WriteLine("The average number is {0}.", averageNum);
}
;;clojure
(defn linq89 []
  (let [numbers [5 4 1 3 9 8 6 7 2 0]
        avg (average numbers)]
    (println "The average number is" avg)))

Output

The average number is 9/2

linq90: Average - Projection

//c#
public void Linq90()
{
    string[] words = { "cherry", "apple", "blueberry" };

    double averageLength = words.Average(w => w.Length);

    Console.WriteLine("The average word length is {0} characters.", averageLength);
}
;;clojure
(defn linq90 []
  (let [words ["cherry", "apple", "blueberry"]
        average-length (average (map count words))]
    (println "The average word length is" average-length "characters.")))

Output

The average word length is 20/3 characters.

linq91: Average - Grouped

//c#
public void Linq91()
{
    List<Product> products = GetProductList();

    var categories =
        from p in products
        group p by p.Category into g
        select new { Category = g.Key, AveragePrice = g.Average(p => p.UnitPrice) };

    ObjectDumper.Write(categories);
}
;;clojure
(defn linq91 []
  (let [products products-list
        categories
        (for [g (group-by :category products)]
          {:category (first g),
           :average-price (average (map :unit-price (second g)))})]
    (doseq [c categories] (println c))))

Output

{:category Beverages, :average-price 37.979166666666664}
{:category Condiments, :average-price 23.0625}
{:category Produce, :average-price 32.37}
{:category Meat/Poultry, :average-price 54.00666666666667}
{:category Seafood, :average-price 20.6825}
{:category Dairy Products, :average-price 28.73}
{:category Confections, :average-price 25.16}
{:category Grains/Cereals, :average-price 20.25}

linq92: Aggregate - Simple

//c#
public void Linq92()
{
    double[] doubles = { 1.7, 2.3, 1.9, 4.1, 2.9 };

    double product = doubles.Aggregate((runningProduct, nextFactor) => runningProduct * nextFactor);

    Console.WriteLine("Total product of all numbers: {0}", product);
}
;;clojure
(defn linq92 []
  (let [dbls [1.7 2.3 1.9 4.1 2.9]
        product (reduce * dbls)]
    (println "Total product of all numbers:" product)))

Output

Total product of all numbers: 88.33080999999999

linq93: Aggregate - Seed

//c#
public void Linq93()
{
    double startBalance = 100.0;

    int[] attemptedWithdrawals = { 20, 10, 40, 50, 10, 70, 30 };

    double endBalance =
        attemptedWithdrawals.Aggregate(startBalance,
            (balance, nextWithdrawal) =>
                ((nextWithdrawal <= balance) ? (balance - nextWithdrawal) : balance));

    Console.WriteLine("Ending balance: {0}", endBalance);
}
;;clojure
(defn linq93 []
  (let [start-balance 100
        attempted-withdrawls [20 10 40 50 10 70 30]
        end-balance (reduce #(identity (if (<= %2 %1) (- %1 %2) %1))
                            start-balance attempted-withdrawls)]
    (println "Ending balance:" end-balance)))

Output

Ending balance: 20

LINQ - Miscellaneous Operators

linq94: Concat - 1

//c#
public void Linq94()
{
    int[] numbersA = { 0, 2, 4, 5, 6, 8, 9 };
    int[] numbersB = { 1, 3, 5, 7, 8 };

    var allNumbers = numbersA.Concat(numbersB);

    Console.WriteLine("All numbers from both arrays:");
    foreach (var n in allNumbers)
    {
        Console.WriteLine(n);
    }
}
;;clojure
(defn linq94 []
  (let [numbers-a [0 2 4 5 6 8 9]
        numbers-b [1 3 5 7 8]
        all-numbers (flatten [numbers-a numbers-b])]
    (println "All numbers from both arrays:")
    (doseq [n all-numbers] (println n))))

Output

All numbers from both arrays:
0
2
4
5
6
8
9
1
3
5
7
8

linq95: Concat - 2

//c#
public void Linq95()
{
    List<Customer> customers = GetCustomerList();
    List<Product> products = GetProductList();

    var customerNames =
        from c in customers
        select c.CompanyName;
    var productNames =
        from p in products
        select p.ProductName;

    var allNames = customerNames.Concat(productNames);

    Console.WriteLine("Customer and product names:");
    foreach (var n in allNames)
    {
        Console.WriteLine(n);
    }
}
;;clojure
(defn linq95 []
  (let [products products-list
        customers customers-list
        customer-names (map :company-name customers)
        product-names (map :product-name products)
        all-names (flatten [customer-names product-names])]
    (println "Customer and product names:")
    (doseq [x all-names] (println x))))

Output

Customer and product names:
Alfreds Futterkiste
Ana Trujillo Emparedados y helados
Antonio Moreno Taquería
Around the Horn
Berglunds snabbköp
Blauer See Delikatessen
...

linq96: EqualAll - 1

//c#
public void Linq96()
{
    var wordsA = new string[] { "cherry", "apple", "blueberry" };
    var wordsB = new string[] { "cherry", "apple", "blueberry" };

    bool match = wordsA.SequenceEqual(wordsB);

    Console.WriteLine("The sequences match: {0}", match);
}
;;clojure
(defn linq96 []
  (let [words-a ["cherry" "apple" "blueberry"]
        words-b ["cherry" "apple" "blueberry"]
        match (= words-a words-b)]
    (println "The sequences match:" match)))

Output

The sequences match: true

linq97: EqualAll - 2

//c#
public void Linq97()
{
    var wordsA = new string[] { "cherry", "apple", "blueberry" };
    var wordsB = new string[] { "apple", "blueberry", "cherry" };

    bool match = wordsA.SequenceEqual(wordsB);

    Console.WriteLine("The sequences match: {0}", match);
}
;;clojure
(defn linq97 []
  (let [words-a ["cherry" "apple" "blueberry"]
        words-b ["apple" "blueberry" "cherry"]
        match (= words-a words-b)]
    (println "The sequences match:" match)))

Output

The sequences match: false

LINQ - Query Execution

linq99: Deferred Execution

//c#
public void Linq99()
{
    // Sequence operators form first-class queries that
    // are not executed until you enumerate over them.

    int[] numbers = new int[] { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };

    int i = 0;
    var q =
        from n in numbers
        select ++i;

    // Note, the local variable 'i' is not incremented
    // until each element is evaluated (as a side-effect):
    foreach (var v in q)
    {
        Console.WriteLine("v = {0}, i = {1}", v, i);
    }
}
;;clojure
(defn linq99 []
  (let [numbers [5 4 1 3 9 8 6 7 2 0]
        i (atom 0)
        q (map (fn [x] (swap! i inc)) (range 10))]
    (println @i (count q) @i)))

Output

0 10 10

linq100: Immediate Execution

//c#
public void Linq100()
{
    // Methods like ToList() cause the query to be
    // executed immediately, caching the results.

    int[] numbers = new int[] { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };

    int i = 0;
    var q = (
        from n in numbers
        select ++i)
        .ToList();

    // The local variable i has already been fully
    // incremented before we iterate the results:
    foreach (var v in q)
    {
        Console.WriteLine("v = {0}, i = {1}", v, i);
    }
}
;;clojure
(defn linq100 []
  (let [numbers [5 4 1 3 9 8 6 7 2 0]
        i (atom 0)
        q (into [] (map (fn [x] (swap! i inc)) (range 10)))]
    (println @i (count q) @i)))

Output

10 10 10

linq101: Query Reuse

//c#
public void Linq101()
{
    // Deferred execution lets us define a query once
    // and then reuse it later after data changes.

    int[] numbers = new int[] { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };
    var lowNumbers =
        from n in numbers
        where n <= 3
        select n;

    Console.WriteLine("First run numbers <= 3:");
    foreach (int n in lowNumbers)
    {
        Console.WriteLine(n);
    }

    for (int i = 0; i < 10; i++)
    {
        numbers[i] = -numbers[i];
    }

    // During this second run, the same query object,
    // lowNumbers, will be iterating over the new state
    // of numbers[], producing different results:
    Console.WriteLine("Second run numbers <= 3:");
    foreach (int n in lowNumbers)
    {
        Console.WriteLine(n);
    }
}
;;clojure
(defn linq101 []
  (def ^:dynamic numbers [5 4 1 3 9 8 6 7 2 0])
  
  (defn low-numbers []
    (filter #(<= % 3) numbers))
  
  (println "First run numbers <= 3:")
  (doseq [n (low-numbers)] (println n))
  
  (println "Second run numbers <= 3")
  (binding [numbers (map #(* -1 %) numbers)]
    (doseq [n (low-numbers)] (println n))))

Output

First run numbers <= 3:
1
3
2
0
Second run numbers <= 3
-5
-4
-1
-3
-9
-8
-6
-7
-2
0

LINQ - Join Operators

Clojure utils added

(defn join [coll with-coll matcher]
  (map (fn [x] {:key x :items (filter (fn [y] (matcher x y)) with-coll)})
       coll))

linq102: Cross Join

//c#
public void Linq102()
{
    string[] categories = new string[]{
        "Beverages",
        "Condiments",
        "Vegetables",
        "Dairy Products",
        "Seafood" };

    List<Product> products = GetProductList();

    var q =
        from c in categories
        join p in products on c equals p.Category
        select new { Category = c, p.ProductName };

    foreach (var v in q)
    {
        Console.WriteLine(v.ProductName + ": " + v.Category);
    }
}
;;clojure
(defn linq102 []
  (let [categories 
        ["Beverages", "Condiments", "Vegetables", "Dairy Products", "Seafood"]
        products products-list
        q (for [pc (join-group categories products #(= %1 (:category %2)))
                x (:items pc)]
            {:category (:key pc), :product-name (:product-name x)})]
    (doseq [v q]
      (println (:product-name v) ":" (:category v)))))

Output

Chai : Beverages
Chang : Beverages
Guaraná Fantástica : Beverages
Sasquatch Ale : Beverages
Steeleye Stout : Beverages
Côte de Blaye : Beverages
Chartreuse verte : Beverages
Ipoh Coffee : Beverages
...

linq103: Group Join

//c#
public void Linq103()
{
    string[] categories = new string[]{
        "Beverages",
        "Condiments",
        "Vegetables",
        "Dairy Products",
        "Seafood" };

    List<Product> products = GetProductList();

    var q =
        from c in categories
        join p in products on c equals p.Category into ps
        select new { Category = c, Products = ps };

    foreach (var v in q)
    {
        Console.WriteLine(v.Category + ":");
        foreach (var p in v.Products)
        {
            Console.WriteLine("   " + p.ProductName);
        }
    }
}
;;clojure
(defn linq103 []
  (let [categories ["Beverages", "Condiments", "Vegetables", "Dairy Products", "Seafood"]
        products products-list
        q (for [pc (join-group categories products #(= %1 (:category %2)))]
            {:category (:key pc), :products (:items pc)})]
    (doseq [pc q]
      (println (:category pc))
      (doseq [product (:products pc)]
        (println " " (:product-name product))))))

Output

Beverages
  Chai
  Chang
  Guaraná Fantástica
  Sasquatch Ale
  Steeleye Stout
  Côte de Blaye
  Chartreuse verte
  Ipoh Coffee
  Laughing Lumberjack Lager
  Outback Lager
  Rhönbräu Klosterbier
  Lakkalikööri
Condiments
  Aniseed Syrup
  Chef Anton's Cajun Seasoning
  Chef Anton's Gumbo Mix
  Grandma's Boysenberry Spread
  Northwoods Cranberry Sauce
  Genen Shouyu
  Gula Malacca
  Sirop d'érable
  Vegie-spread
  Louisiana Fiery Hot Pepper Sauce
  Louisiana Hot Spiced Okra
  Original Frankfurter grüne Soße
...

linq104: Cross Join with Group Join

//c#
public void Linq104()
{
    string[] categories = new string[]{
        "Beverages",
        "Condiments",
        "Vegetables",
        "Dairy Products",
        "Seafood" };

    List<Product> products = GetProductList();

    var q =
        from c in categories
        join p in products on c equals p.Category into ps
        from p in ps
        select new { Category = c, p.ProductName };

    foreach (var v in q)
    {
        Console.WriteLine(v.ProductName + ": " + v.Category);
    }
}
;;clojure
(defn linq104 []
  (let [categories 
        ["Beverages", "Condiments", "Vegetables", "Dairy Products", "Seafood"]
        products products-list
        q (for [pc (join-group categories products #(= %1 (:category %2)))
                p (:items pc)]
            {:category (:key pc),
             :product-name (:product-name p)})]
    (doseq [p q]
      (println (:product-name p) ":" (:category p)))))

Output

Chai : Beverages
Chang : Beverages
Guaraná Fantástica : Beverages
Sasquatch Ale : Beverages
Steeleye Stout : Beverages
Côte de Blaye : Beverages
Chartreuse verte : Beverages
Ipoh Coffee : Beverages
Laughing Lumberjack Lager : Beverages
Outback Lager : Beverages
Rhönbräu Klosterbier : Beverages
Lakkalikööri : Beverages
Aniseed Syrup : Condiments
Chef Anton's Cajun Seasoning : Condiments
Chef Anton's Gumbo Mix : Condiments
...

linq105: Left Outer Join

//c#
public void Linq105()
{
    string[] categories = new string[]{
        "Beverages",
        "Condiments",
        "Vegetables",
        "Dairy Products",
        "Seafood" };

    List<Product> products = GetProductList();

    var q =
        from c in categories
        join p in products on c equals p.Category into ps
        from p in ps.DefaultIfEmpty()
        select new { Category = c, ProductName = p == null ? "(No products)" : p.ProductName };

    foreach (var v in q)
    {
        Console.WriteLine(v.ProductName + ": " + v.Category);
    }
}
;;clojure
(defn linq105 []
  (let [categories 
        ["Beverages", "Condiments", "Vegetables", "Dairy Products", "Seafood"]
        products products-list
        q (flatten
           (for [pc (join-group categories products #(= %1 (:category %2)))]
             (if (empty? (:items pc))
               {:category (:key pc), :product-name "(No products)"}
               (for [p (:items pc)]
                 {:category (:key pc),
                  :product-name (:product-name p)}))))]
    (doseq [p q]
      (println (:product-name p) ":" (:category p)))))

Output

Chai: Beverages
Chang: Beverages
Guaraná Fantástica: Beverages
Sasquatch Ale: Beverages
Steeleye Stout: Beverages
Côte de Blaye: Beverages
Chartreuse verte: Beverages
Ipoh Coffee: Beverages
Laughing Lumberjack Lager: Beverages
Outback Lager: Beverages
Rhönbräu Klosterbier: Beverages
Lakkalikööri: Beverages
Aniseed Syrup: Condiments
Chef Anton's Cajun Seasoning: Condiments
Chef Anton's Gumbo Mix: Condiments
Grandma's Boysenberry Spread: Condiments
Northwoods Cranberry Sauce: Condiments
Genen Shouyu: Condiments
Gula Malacca: Condiments
Sirop d'érable: Condiments
Vegie-spread: Condiments
Louisiana Fiery Hot Pepper Sauce: Condiments
Louisiana Hot Spiced Okra: Condiments
Original Frankfurter grüne Soße: Condiments
(No products): Vegetables
...

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