Add exercises to Chapter 02.

src/FPinFSharp.Exercises/Chapter_02/Exercises.fs

@@ -0,0 +1,69 @@
+namespace FPinFSharp.Exercises.Chapter_02
+
+open System;
+
+module Exercises =
+
+    // 2.1 Declare a function f: int -> bool such that f(n) = true
+    // exactly when n is divisible by 2 or divisible by 3 but not divisible by 5.
+    // Write down the expected values of f(24), f(27), f(29) and f(30) and compare with the result.
+    let f (x: int) : bool =
+        (x % 2 = 0 || x % 3 = 0) && x % 5 <> 0
+
+    // 2.2 Declare a function: string * int -> string, where: pow(s,n) = s · s · ... · s
+    // We use '·' to denote string concatenation. (The F# representation is '+'.).
+    let rec concatenateStringV1 (s: string, n: int) : string =
+        if n <= 0
+        then ""
+        else s + concatenateStringV1(s, n - 1)
+
+    let rec concatenateStringV2 (s: string, n: int) : string =
+        match n with
+        | _ when n <= 0 -> ""
+        | _ -> s + concatenateStringV2(s, n - 1)
+
+    // 2.3 Declare a function isIthChar: string * int * char -> bool
+    // where the value of isIthChar(str, i, ch) is true if and only
+    // if ch is the i’th character in the string str (numbering starting at zero).
+    let isIthCharV1 (str: string, i: int, ch: char) : bool =
+        if i < 0 then ArgumentOutOfRangeException() |> raise
+        str.IndexOf(ch) = i
+
+    let isIthCharV2 (str: string, i: int, ch: char) : bool =
+        if i < 0 then ArgumentOutOfRangeException() |> raise
+        let positions = 
+            let rec inner (part: string, from: int, x: char) =
+                match from with
+                | _ when from >= str.Length -> []
+                | _ ->
+                    if x = part.[from]
+                    then from :: inner(part, from + 1, ch)
+                    else inner(part, from + 1, ch)
+            inner(str, 0, ch)
+        List.contains i positions
+
+    // 2.4 Declare a function occFromIth: string * int * char -> int
+    // where occFromIth(str, i, ch) = the number of occurrences of character 'ch' in positions 'j'
+    // in the string 'str' with j ≥ i.
+    // Hint: the value should be 0 for i ≥ size str.
+    let rec occFromIth (str: string, from: int, ch: char) : int =
+        if from < 0 then ArgumentOutOfRangeException() |> raise
+        match from with
+        | _ when from >= str.Length -> 0
+        | _ ->
+            let current = str[from]
+            let sum = occFromIth(str, from + 1, ch)
+            if current = ch
+            then sum + 1
+            else sum
+
+    // 2.5 Declare the F# function occInString: string * char -> int
+    // where occInString(str, ch) = the number of occurrences of character ch in the string str.
+    let rec occInString (str: string, ch: char) : int =
+        let mutable sum = 0;
+        match str.Length with
+        | 0 -> sum
+        | _ ->
+            if ch = str.[0] then
+                sum <- sum + 1
+            sum + occInString(str.Substring(1), ch)

src/FPinFSharp.Exercises/FPinFSharp.Exercises.fsproj

@@ -30,6 +30,7 @@
     <Compile Include="Chapter_02\Section_02_10.fs" />
     <Compile Include="Chapter_02\Section_02_11.fs" />
     <Compile Include="Chapter_02\Section_02_12.fs" />
+    <Compile Include="Chapter_02\Exercises.fs" />
     <Content Include="Chapter_03\Description.md" />
   </ItemGroup>
 

tests/FPinFSharp.Exercises.UnitTests/Chapter_02/Exercises_Tests.fs

@@ -0,0 +1,76 @@
+namespace FPinFSharp.Exercises.UnitTests.Chapter_02
+
+open FPinFSharp.Exercises.Chapter_02.Exercises
+open Shouldly
+open Xunit
+
+module Exercises_Tests =
+
+    // 2.1
+    [<Theory>]
+    [<InlineData(6, true)>]
+    [<InlineData(24, true)>]
+    [<InlineData(27, true)>]
+    [<InlineData(29, false)>]
+    [<InlineData(30, false)>]
+    let ``GIVEN x WHEN f THEN result as expected`` (x: int) (expectedResult: bool) =
+        let actualResult = f x
+        actualResult.ShouldBe(expectedResult)
+
+    // 2.2
+    [<Theory>]
+    [<InlineData("A", 3, "AAA")>]
+    [<InlineData("1 ", 5, "1 1 1 1 1 ")>]
+    [<InlineData(" x", 7, " x x x x x x x")>]
+    let ``GIVEN s and n WHEN concatenateStringV1 THEN result as expected`` (s: string) (n: int) (expectedResult: string) =
+        let actualResult = concatenateStringV1(s, n)
+        actualResult.ShouldBe(expectedResult)
+
+    [<Theory>]
+    [<InlineData("A", 3, "AAA")>]
+    [<InlineData("1 ", 5, "1 1 1 1 1 ")>]
+    [<InlineData(" x", 7, " x x x x x x x")>]
+    let ``GIVEN s and n WHEN concatenateStringV2 THEN result as expected`` (s: string) (n: int) (expectedResult: string) =
+        let actualResult = concatenateStringV2(s, n)
+        actualResult.ShouldBe(expectedResult)
+
+    [<Theory>]
+    [<InlineData("This is my string", 13, 'r', true)>]
+    [<InlineData("This is my string", 1, 'T', false)>]
+    [<InlineData("This is my string", 4, ' ', true)>]
+    [<InlineData("This is my string", 7, ' ', false)>]
+    [<InlineData("This is my string", 3, 's', true)>]
+    [<InlineData("This is my string", 6, 's', false)>]
+    let ``GIVEN str, i and ch  WHEN isIthCharV1 THEN result as expected``
+        (str: string) (i: int) (ch: char) (expectedResult: bool) =
+        let actualResult = isIthCharV1(str, i, ch)
+        actualResult.ShouldBe(expectedResult)
+
+    [<Theory>]
+    [<InlineData("This is my string", 13, 'r', true)>]
+    [<InlineData("This is my string", 1, 'T', false)>]
+    [<InlineData("This is my string", 4, ' ', true)>]
+    [<InlineData("This is my string", 7, ' ', true)>]
+    [<InlineData("This is my string", 3, 's', true)>]
+    [<InlineData("This is my string", 6, 's', true)>]
+    let ``GIVEN str, i and ch  WHEN isIthCharV2 THEN result as expected``
+        (str: string) (i: int) (ch: char) (expectedResult: bool) =
+        let actualResult = isIthCharV2(str, i, ch)
+        actualResult.ShouldBe(expectedResult)
+
+    [<Theory>]
+    [<InlineData("This is my string", 0, 'i', 3)>]
+    let ``GIVEN str, i and ch  WHEN occFromIth THEN result as expected``
+        (str: string) (from: int) (ch: char) (expectedResult: int) =
+        let actualResult = occFromIth(str, from, ch)
+        actualResult.ShouldBe(expectedResult)
+
+    [<Theory>]
+    [<InlineData("This is my first string", 't', 2)>]
+    [<InlineData("This is my second string", 's', 4)>]
+    [<InlineData("This is my third string", 'r', 2)>]
+    [<InlineData("This is my fourth string", 'x', 0)>]
+    let ``GIVEN string and char WHEN occInString THEN result as expected``
+        (str: string) (ch: char) (expectedResult: int) =
+        let actualResult = occInString(str, ch)
+        actualResult.ShouldBe(expectedResult)

tests/FPinFSharp.Exercises.UnitTests/FPinFSharp.Exercises.UnitTests.fsproj

@@ -31,6 +31,7 @@
     <Compile Include="Chapter_02\Section_02_10_Tests.fs" />
     <Compile Include="Chapter_02\Section_02_11_Tests.fs" />
     <Compile Include="Chapter_02\Section_02_12_Tests.fs" />
+    <Compile Include="Chapter_02\Exercises_Tests.fs" />
     <Folder Include="Chapter_03\" />
   </ItemGroup>