Merge pull request #41 from jetbrains-academy/mikhail/scala-edit

Mikhail/scala edit

Author: sofiiako

Classes Vs Case Classes/Case Classes Encoding/task.md

@@ -11,11 +11,11 @@ because it is very common in practice.
 So, when we define a case class, the Scala compiler defines a class
 enhanced with some more methods and a companion object.
 
-For instance, the following case class definition:
+For instance, look at the following case class definition:
 
       case class Note(name: String, duration: String, octave: Int)
 
-Expands to the following class definition:
+It expands to the following class definition:
 
       class Note(_name: String, _duration: String, _octave: Int) extends Serializable {
 

Classes Vs Case Classes/Creation and Manipulation/task.md

@@ -1,10 +1,10 @@
 
-In the previous sections we have seen how case classes could be
-used to achieve information aggregation, and also how classes
+In the previous sections, we have seen how case classes could be
+used to achieve information aggregation and also how classes
 could be used to achieve data abstraction or to define stateful
 objects.
 
-What are the relationship between classes and case classes? How
+What is the relationship between classes and case classes? How
 do they differ?
 
 ## Creation and Manipulation

Classes Vs Case Classes/Equality/task.md

@@ -14,7 +14,7 @@ values, whereas the same definitions of notes lead to equal values.
 
 As we have seen in the previous sections, stateful classes introduce a notion of *identity*
 that does not exist in case classes. Indeed, the value of `BankAccount` can change over
-time whereas the value of a `Note` is immutable.
+time, whereas the value of `Note` is immutable.
 
 In Scala, by default, comparing objects will compare their identity, but in the
 case of case class instances, the equality is redefined to compare the values of
@@ -38,5 +38,5 @@ implement their equality).
 
 ## Exercise
 
-- Complete the creation of two instances of the `BankAccount`.
-- Complete the creation of two instances of a `c3` `Note`.
+- Complete the creation of two instances of `BankAccount`.
+- Complete the creation of two instances of `c3` `Note`.

Definitions and Evaluation/Multiple Parameters/task.md

@@ -7,17 +7,17 @@ Separate several parameters with commas:
 
 ## Parameters and Return Types 
 
-Function parameters come with their type, which is given after a colon
+Function parameters come with their type, which is given after a colon:
 
     def power(x: Double, y: Int): Double = ...
 
 If a return type is given, it follows the parameter list.
 
 ## Val vs Def
 
-The right hand side of a `def` definition is evaluated on each use.
+The right-hand side of a `def` definition is evaluated on each use.
 
-The right hand side of a `val` definition is evaluated at the point of the definition
+The right-hand side of a `val` definition is evaluated at the point of the definition
 itself. Afterwards, the name refers to the value.
 
     val x = 2
@@ -27,11 +27,11 @@ For instance, `y` above refers to `4`, not `square(2)`.
 
 ## Evaluation of Function Applications
 
-Applications of parametrized functions are evaluated in a similar way as
+Applications of parametrized functions are evaluated in a way similar to
 operators:
 
  1. Evaluate all function arguments, from left to right.
- 2. Replace the function application by the function's right-hand side, and, at the same time
+ 2. Replace the function application by the function's right-hand side and, at the same time
  3. Replace the formal parameters of the function by the actual arguments.
 
 ## Example
@@ -52,7 +52,7 @@ This scheme of expression evaluation is called the *substitution model*.
 The idea underlying this model is that all evaluation does is *reduce
 an expression to a value*.
 
-It can be applied to all expressions, as long as they have no side effects.
+It can be applied to all expressions as long as they have no side effects.
 
 The substitution model is formalized in the λ-calculus, which gives
 a foundation for functional programming.
@@ -69,8 +69,8 @@ No. Here is a counter-example:
 
 ## Value Definitions and Termination
 
-The difference between `val` and `def` becomes apparent when the right
-hand side does not terminate. Given
+The difference between `val` and `def` becomes apparent when the right-hand
+side does not terminate. Given
 
       def loop: Int = loop
 
@@ -124,5 +124,5 @@ Scala normally uses call-by-value.
 ## Exercise
 
 Complete the following definition of the `triangleArea` function,
-which takes a triangle base and height as parameters and returns
+which takes the base and height of a triangle as parameters and returns
 its area.

Definitions and Evaluation/Naming Things/task.md

@@ -1,25 +1,25 @@
 
 ## Naming Things
 
-Consider the following program that computes the area of a disc
+Consider the following program, which computes the area of a disc
 whose radius is `10`:
 
     3.14159 * 10 * 10
 
-To make complex expressions more readable we can give meaningful names to
+To make complex expressions more readable, we can give meaningful names to
 intermediate expressions:
 
     val radius = 10
     val pi = 3.14159
 
     pi * radius * radius
 
-Besides making the last expression more readable it also allows us to
+Besides making the last expression more readable, it also allows us to
 not repeat the actual value of the radius.
 
 ## Evaluation
 
-A name is evaluated by replacing it with the right hand side of its definition
+A name is evaluated by replacing it with the right-hand side of its definition.
 
 ### Example
 

Functional Loops/Computing the Square Root of a Value/task.md

@@ -1,7 +1,7 @@
 
 ## Computing the Square Root of a Value 
 
-We will define in this section a method
+In this section, we will define a square root calculation method:
 
     /** Calculates the square root of parameter x */
     def sqrt(x: Double): Double = ...
@@ -38,7 +38,7 @@ Recursive methods need an explicit return type in Scala.
 
 For non-recursive methods, the return type is optional.
 
-Second, we define a method `improve` to improve an estimate and a test to check for termination:
+Second, we define a method `improve` to improve the estimate and a test to check for termination:
 
       def improve(guess: Double, x: Double) =
         (guess + x / guess) / 2

Functional Loops/Conditional Expressions/task.md

@@ -1,28 +1,28 @@
 
 ## Conditional Expressions
 
-To express choosing between two alternatives, Scala
-has a conditional expression `if-else`.
+To express the choice between two alternatives, Scala
+uses a conditional expression `if-else`.
 
-It looks like a `if-else` in Java, but is used for expressions, not statements.
+It looks like the `if-else` in Java but is used for expressions, not statements.
 
 Example:
 ~~~
     def abs(x: Double) = if (x >= 0) x else -x
 ~~~
-`x >= 0` is a *predicate*, of type `Boolean`.
+Here `x >= 0` is a *predicate* of type `Boolean`.
 
 ## Boolean Expressions 
 
-Boolean expressions `b` can be composed of
+Boolean expressions `b` can include:
 
     true  false      // Constants
     !b               // Negation
     b && b           // Conjunction
     b || b           // Disjunction
 
-and of the usual comparison operations:
-      e <= e, e >= e, e < e, e > e, e == e, e != e
+They can also contain the usual comparison operations:
+      e <= e, e >= e, e < e, e > e, e == e, e != e.
 
 ## Rewrite rules for Booleans
 
@@ -41,11 +41,11 @@ We say these expressions use "short-circuit evaluation".
 
 ## Summary
 
-You have seen simple elements of functional programing in Scala.
+You have seen simple elements of functional programing in Scala:
 
- - arithmetic and boolean expressions
- - conditional expressions if-else
- - functions with recursion
+ - arithmetic and boolean expressions;
+ - conditional expressions if-else;
+ - functions with recursion.
 
 You have learned the difference between the call-by-name and
 call-by-value evaluation strategies.
@@ -55,4 +55,4 @@ the substitution model.
 
 ## Exercise
 
-Complete the following method definition that computes the factorial of a number.
+Complete the definition of the following method, which computes the factorial of a number.

Higher Order Functions/Higher Order Functions/task.md

@@ -8,27 +8,27 @@ can be passed as a parameter and returned as a result.
 
 This provides a flexible way to compose programs.
 
-Functions that take other functions as parameters or that return functions
-as results are called *higher order functions*.
+Functions that take other functions as parameters or return functions
+as a result are called *higher order functions*.
 
 ###  Motivation 
 
 Consider the following programs.
 
-Take the sum of the integers between `a` and `b`:
+Taking the sum of the integers between `a` and `b`:
 
       def sumInts(a: Int, b: Int): Int =
         if (a > b) 0 else a + sumInts(a + 1, b)
 
-Take the sum of the cubes of all the integers between `a`
+Taking the sum of the cubes of all the integers between `a`
 and `b`:
 
       def cube(x: Int): Int = x * x * x
 
       def sumCubes(a: Int, b: Int): Int =
         if (a > b) 0 else cube(a) + sumCubes(a + 1, b)
 
-Take the sum of the factorials of all the integers between `a`
+Taking the sum of the factorials of all the integers between `a`
 and `b`:
 
       def sumFactorials(a: Int, b: Int): Int =
@@ -72,22 +72,22 @@ Passing functions as parameters leads to the creation of many small functions.
 
 Sometimes it is tedious to have to define (and name) these functions using `def`.
 
-Compare to strings: We do not need to define a string using `val`. Instead of:
+Compare to strings: we do not need to define a string using `val`. Instead of:
 
       val str = "abc"; println(str)
 
-We can directly write:
+we can directly write:
 
       println("abc")
 
-because strings exist as *literals*. Analogously we would like function
+because strings exist as *literals*. Analogously, we can use function
 literals, which let us write a function without giving it a name.
 
 These are called *anonymous functions*.
 
 ### Anonymous Function Syntax
 
-Example of a function that raises its argument to a cube:
+Example of a function that raises its argument to the third power:
 
       (x: Int) => x * x * x
 
@@ -108,7 +108,7 @@ can always be expressed using `def` as follows:
 
       { def f(x1: T1, …, xn: Tn) = e ; f }
 
-where `f` is an arbitrary, fresh name (that's not yet used in the program).
+where `f` is an arbitrary, fresh name (that has not yet been used in the program).
 
 One can therefore say that anonymous functions are *syntactic sugar*.
 

Imperative Programming/Imperative Loops/task.md

@@ -3,7 +3,7 @@
 
 In the first sections, we saw how to write loops using recursion.
 
-### While-Loops 
+### While Loops 
 
 We can also write loops with the `while` keyword:
 
@@ -14,18 +14,18 @@ We can also write loops with the `while` keyword:
         r
       }
 
-As long as the condition of a *while* statement is `true`,
+As long as the condition of the `while` statement is `true`,
 its body is evaluated.
 
-### For-Loops 
+### For Loops 
 
-In Scala there is a kind of `for` loop:
+In Scala, there is a kind of `for` loop, too:
 
       for (i <- 1 until 3) { System.out.print(i.toString + " ") }
 
 This displays `1 2`.
 
-For-loops translate similarly to for-expressions, but using the
+`For` loops translate similarly to `for` expressions but use the
 `foreach` combinator instead of `map` and `flatMap`.
 
 `foreach` is defined on collections with elements of type `A` as follows:
@@ -37,7 +37,7 @@ Example:
 
       for (i <- 1 until 3; j <- "abc") println(s"$i $j")
 
-translates to:
+It translates to:
 
       (1 until 3) foreach (i => "abc" foreach (j => println(s"$i $j")))