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(ns tryclojure.tutorial
(:use hiccup.core))
(defn code [s] (html [:code.code s]))
(def tutorial0-text
"This tutorial is intended for people who have never used Clojure before but have experience with "
" other programming languages. This is not meant to be a comprehensive tutorial"
", but instead intended to get you started with Clojure -- and hopefully interested enough to continue. "
"Please bear in mind that this tutorial is evolving, so check back frequently for new additions." [:br] [:br]
"Above, you have your REPL. Please try the examples as we go along, and by all means experiment"
" with concepts indpendently. Should you refuse, you will promptly be IP banned from this website, and a teddy "
"bear will eat your candies. ;-)"[:br] [:br] "Don't make teddy eat your candy."]
[:p.bottom "Hit the pretty little 'Next' button to continue for the love of Pete!"]))
(def tutorial1-text
"Let's jump right in there and write some Clojure. Let's start out with the familiar 'Hello, World!' People "
"seem to love it so much. Type the following into the REPL: "]
(code "(println \"!dlrow ,olleH\")")
"Something isn't right here! (I'm not talking about the fact that this website's lack of panache) "
"It seems that 'Hello World' has been mangled! It's okay though, because we're smart "
"and we can figure out how to remedy this situation. If you're wondering why it printed our gibberish AND 'nil' "
"it's because 'nil' (which essentially means 'nothing') is println's return value."
"Let's experiment until we figure out what went wrong. "
"It seems that the " (code "reverse") " should fix things -- so type the following into the REPL: "]
(code "(reverse \"!dlrow ,olleH\")")
"Hmm. It did indeed set it right, but this isn't what we were looking for! That doesn't even look like a string. "
"Reverse took our string, reversed it, and now we have a sequence of characters. You can tell this because each "
"character has a '\\' (backslash in layman's terms) preceeding it. Clojure uses those to denote Character (big 'C' character) literals. "
"We need a string though! "
"What do we do when we need a string, but we have something else that isn't stringy (a highly technical term)? No, we don't go to the shop "
"and buy string cheese (not to disparage string cheese mind you), but instead we use the lovely " (code "str") " function! Try this: "]
(code "(str (reverse \"!dlrow ,olleH\"))")
"Ooh! So close. It appears that the str function is making the entire sequence a string! Sequences can be made to "
" look like strings. str works on any number of arguments. You can pass str any number of arguments and it will "
"call Java's toString method on each of them to change them into a string, and then it will concatenate them "
"all into one mammoth string. Unfortunately, all of our characters are stuck in this sequence! How can we get them out "
"of the sequence, and pass them all to str? Do not fear, young Clojurian, for I have the answer. We use the "
(code "apply") " function. " (code "apply") " takes a function and a sequence, and 'unrolls' the sequence, "
"passing all of its elements to the function as arguments. Basically, it takes the sequence "
"and dumps its elements into the argument list of the supplied function; which is exactly what we need. "
"Let's see if it works... try this: "]
(code "(apply str (reverse \"!dlrow ,olleH\"))")
"Ka-chow! There we go. Impressive. I'm proud of you, I really am. Now, for the final test. Let's tell the world "
"just how much they mean to us by making the world rotate in the other direction! Let's do this: "]
(code "(println (apply str (reverse \"!dlrow ,olleH\")))")
"Congratulations, you have passed step one. Press Next to continue."]))
(def tutorial2-text
"Alright. We have greeted the world. Now what? Math? Clojure is great at math. Thanks to the uniformity of "
"prefix notation, we don't have to worry about precedence rules; which we kinda loathe anyway. This goes before that, and that goes before that other thing... blah! In Clojure, mathematical operators work like any other function."
" The common operators are +, -, *, and /. Let's try them out: "]
(code "(+ 2 2)\n(- 3 2)\n(* 5 5)\n(/ 4 3)")
"So, that was great. But that last one doesn't quite look right. The problem is that Clojure has a built in "
"Ratio type. You can confirm this by doing this: " (code "(class (/ 4 3))") "."]
"So how do we perform divison that we are familiar with? If you want decimal division, use a floating-point literal for either "
"the numerator or denominator: " (code "(/ 4.0 3)") ". If you want to stick to integer math, you can use the " (code "quot") " function, "
"or the " (code "rem") " function to get the remainder."]
"All of the math functions take an arbitrary number of arguments. This means you can do stuff like this: "
(code "(+ 1 2 3 4 5 6)") ". Go ahead, try it out. You know you want to. Play around with the math functions for "
"a while. I'll wait. Go ahead."]
[:p.bottom "That's the end of step two. Press Next to continue to step three, where we'll play with sequences."]))
(def tutorial3-text
"Now that we've covered the basics of prefix math, let's take some time to play with sequences."]
"In Clojure, the term 'sequence' is an abstraction that many data structures "
"implement. This abstraction allows any function that works on a 'seq' (pronounced seek) to work on any data "
"structure that is seqable. This means all Clojure and Java collections, strings, and even I/O streams."]
"In isolation this doesn't make sense, so let's play with vectors. A literal vector looks like this: " (code "[1 2 3 \"four\" 5 6.0]") ". Vectors are the "
"most commonly used collection in Clojure, along with maps. Let's see if we can square all of the elements "
"of a vector: " (code "(map (fn [x] (* x x)) [1 2 3 4 5])") ". Try that out. The " (code "map") " function takes "
"a function that takes a single argument and returns a value, which it 'applies' to each element of its second argument, a sequence. "
"The resulting sequence is then returned."]
"We have introduced something new here -- the anonymous function. Anonymous functions are used quite heavily in Clojure code. "
"The are created using " (code "fn") ". After fn, you supply a vector of arguments that the "
"function takes, and then the body of the function that uses those arguments to computer a value. Clojure has "
"short hand for anonymous functions as well. The above anonymous function can be rewritten using a shorthand form: "
(code "#(+ % %)") ". When you use this shorthand, the function arguments are accessed like so: % or %1 for the "
"first argument, %2 for the second argument, %3 for the third and so on. Our code now looks like this: "
(code "(map #(* % %) [1 2 3 4 5])")]
"Another highly important collection is the hashmap. A literal hashmap looks like this: "
(code "{:key \"value\" :key2 3 :key4 [3 4 2 1]}") ". The keys in this map are something called 'keywords'. "
"You can tell that they are keywords because they start with a colon ':' character. They're like symbols that "
"resolve to themselves. In idiomatic Clojure code, keywords are often used as map keys. You can use many objects as map keys, "
"including integers, vectors, strings, and other maps."]
"To get a value at a key in a map, we can do this: " (code "({:key1 :val} :key1)") ". I bet you're all lolwut "
"right now, aren't you? In Clojure, hashmaps are functions that take a single argument, which should be a key "
"and they lookup the key within themselves and return the value at the key or nil if the key doesn't exist. "
"Another neat trick for maps with keywords for keys is this: " (code "(:key1 {:key1 :val})") ". Keywords are "
"also functions. They just look themselves up in the supplied map."]
"Clojure has all sorts of other data structures as well. Sets, lists, queues, zippers, etc. We'll talk about some of "
"those later on. For now, lets move on to step four. Press Next to continue."]))
(def tutorial4-text
"We've learned a little about Clojure's sequences, so let's use them to do some stuff. I've been wondering how "
"vowels are in the word \"teddybear\". Aren't you wondering the same thing? It's absolutely agonizing not "
"knowing! We're programmers, you and I, so we shouldn't have to count those vowels ourselves. Indeed, we don't "
"We can use Clojure to count them for us!"]
"Okay, we'll start with the string \"teddybear\". We're going to be using this string a lot, and we don't want "
"to have to keep typing it over and over again, do we? Luckily, Clojure can help us here. Type this into the "
"REPL: " (code "(def teddy \"teddybear\")") ". What def does is pretty simple: it simply gives a name to a "
"value so that we can refer to it by that name later. Don't worry about what the REPL printed when you typed "
"that, it's just trying to show you exactly where the var is mapped (in this case, a sandbox generated namespace. "
"We need to make sure it worked. Type this into the REPL: " (code "teddy") ". Cool huh?"]
"Now that we are armed with a loaded teddybear, we can start figuring out how to find out the number of vowels. "
"For this, we need to introduce a new collection type: sets. A literal set looks like this: " (code "#{3 4 5 \"x\" \\y}")
". A set can hold anything, but it can't hold any two of the same thing. In a set, there can be no duplicate objects. "
"Another important fact about sets is that they, like maps, are also functions. A set is a function that takes "
"an argument and looks inside itself to see if that same object is inside of it. If this is true, it returns the "
"object, or returns nil. Let's try this out for ourselves: "]
(code "(#{1 2 3} 3)\n(#{\"abc\" \\e} \\e)\n(#{3 4 \\x} 5)")
"Okay, so how is this useful? It really isn't. Not alone, anyway. However, when it's combined with other sequence "
"functions, it can be used to make a really elegant solution to a problem like this."]
"Okay, so we have a way to test if a character is a vowel. We can simply do this: " (code "(#{\\a \\e \\i \\o \\u} e)")
". Since we're going to be using the set of vowels a lot, go ahead and give it a name in the REPL: "
(code "(def vowels #{\\a \\e \\i \\o \\u})") ". Now we can use " (code "vowels") " to refer to the set of vowels. "]
"Now, we have a way to find out if a character is a vowel, now we just need a way to remove everything that isn't "
"a vowel from our teddybear string. I have just the function! We need " (code "filter") ". Filter takes what "
"is called a 'predicate', that is, a function that returns true or false, and it applies this function to each "
"element of a sequence in turn. If the predicate function returns false or nil for an element, that element is "
"removed from the sequence. If the predicate function returns anything that isn't false or nil for an element, "
"that element is left alone. In Clojure, anything that isn't false or nil is considered a true value."]
"Let's try filter out a bit. Let's try to filter out all odd numbers from a sequence of numbers. Clojure has "
"a function called " (code "odd?") " that we can use. Putting a question mark at the end is a Clojure naming convention "
"for functions that are predicates (return either true or false). Try it out in the REPL:"]
(code "(odd? 1)\n(odd? 2)")
"Okay, now we need a sequence of numbers. We could type these out by hand, but that's tedious, and as Clojure "
"programmers, we do not tolerate 'tedious'. We can use Clojure's range function to generate these numbers for us. "
(code "range") ", if given one integer, will generate a sequence of numbers from 0 to the integer that you passed to "
"it. Try this: " (code "(range 10)") ". We have a sequence of numbers from 0 to 9. Apparently, the upper-bound "
"(the number you passed to range) is 'inclusive', meaning it's not included in the resulting range. If we really "
"wanted a sequence of numbers from 0 to 10, we'd do this: " (code "(range 11)") "."]
"We don't really want the zero, so let's give range a lower-bound, along with an upper-bound. It can take two "
"arguments: " (code "(range 1 11)") ". There we go! We have all of the numbers from 1 to 10. Now, let's use "
"filter and the odd? function to get all of the odd numbers out of the sequence. Try this: "
(code "(filter odd? (range 1 11))") ". Ka-chow! That's magic, isn't it? Work of art, that is."]
"Now that we know how to use filter, we can now use it to filter out all of the vowels in our teddy string. "
"We have our string defined in teddy, and our set of vowels in vowels, so we should try this: "
(code "(filter vowels teddy)")
". That was easy enough. Now we have a sequence of characters. But we still need to count them! Luckily, "
"Clojure has just the function for that: " (code "count") "! It takes a sequence and counts (whoda thunk it) the "
"number of elements in the sequence. Let's try it out: " (code "(count (filter vowels teddy))") ". Yeehaw!"
" You did it! Once again, you never cease to amaze me. You're catching on quickly."]
[:p.bottom "That's the end of step 4. Press Next to move on."]))
(def tutorial
[:input#back {:type "button" :value "Back"}]
[:input#continue {:type "button" :value "Next"}]]))
(defn get-tutorial [step]
(condp = step
"0" tutorial
"1" tutorial0-text
"2" tutorial1-text
"3" tutorial2-text
"4" tutorial3-text
"5" tutorial4-text
"6" "TODO!"))
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