Merge pull request #1 from danielboros/Chapter1

Complete Chapter 1

src/Chapter1.hs

@@ -204,31 +204,31 @@ So, the output in this example means that 'False' has type 'Bool'.
 > Try to guess first and then compare your expectations with GHCi output
 
 >>> :t True
-<INSERT THE RESULT INSTEAD OF THE TEXT>
+True :: Bool
 >>> :t 'a'
-<INSERT THE RESULT INSTEAD OF THE TEXT>
+'a' :: Char
 >>> :t 42
-<INSERT THE RESULT INSTEAD OF THE TEXT>
+42 :: Num p => p
 
 A pair of boolean and char:
 >>> :t (True, 'x')
-<INSERT THE RESULT INSTEAD OF THE TEXT>
+(True, 'x') :: (Bool, Char)
 
 Boolean negation:
 >>> :t not
-<INSERT THE RESULT INSTEAD OF THE TEXT>
+not :: Bool -> Bool
 
 Boolean 'and' operator:
 >>> :t (&&)
-<INSERT THE RESULT INSTEAD OF THE TEXT>
+(&&) :: Bool -> Bool -> Bool
 
 Addition of two numbers:
 >>> :t (+)
-<INSERT THE RESULT INSTEAD OF THE TEXT>
+(+) :: Num a => a -> a -> a
 
 Maximum of two values:
 >>> :t max
-<INSERT THE RESULT INSTEAD OF THE TEXT>
+max :: Ord a => a -> a -> a
 
 You might not understand each type at this moment, but don't worry! You've only
 started your Haskell journey. Types will become your friends soon.
@@ -296,31 +296,31 @@ expressions in GHCi
   functions and operators first. Remember this from the previous task? ;)
 
 >>> 1 + 2
-INSERT THE RESULT INSTEAD OF THE TEXT
+3
 >>> 10 - 15
-
+-5
 >>> 10 - (-5)  -- negative constants require ()
-
+15
 >>> (3 + 5) < 10
-
+True
 >>> True && False
-
+False
 >>> 10 < 20 || 20 < 5
-
+True
 >>> 2 ^ 10  -- power
-
+1024
 >>> not False
-
+True
 >>> div 20 3  -- integral division
-
+6
 >>> mod 20 3  -- integral division remainder
-
+2
 >>> max 4 10
-
+10
 >>> min 5 (max 1 2)
-
+2
 >>> max (min 1 10) (min 5 7)
-
+5
 
 Because Haskell is a __statically-typed__ language, you see an error each time
 you try to mix values of different types in situations where you are not
@@ -412,6 +412,7 @@ task is to specify the type of this function.
 49
 -}
 
+squareSum :: Int -> Int -> Int
 squareSum x y = (x + y) * (x + y)
 
 
@@ -432,7 +433,7 @@ Implement the function that takes an integer value and returns the next 'Int'.
   function body with the proper implementation.
 -}
 next :: Int -> Int
-next x = error "next: not implemented!"
+next x = x + 1
 
 {- |
 After you've implemented the function (or even during the implementation), you
@@ -472,8 +473,9 @@ Implement a function that returns the last digit of a given number.
   results. Or you can try to guess the function name, search for it and check
   whether it works for you!
 -}
--- DON'T FORGET TO SPECIFY THE TYPE IN HERE
-lastDigit n = error "lastDigit: Not implemented!"
+lastDigit :: Int -> Int
+lastDigit n = mod x 10
+  where x = abs n
 
 
 {- |
@@ -503,7 +505,7 @@ branches because it is an expression and it must always return some value.
   satisfying the check will be returned and, therefore, evaluated.
 -}
 closestToZero :: Int -> Int -> Int
-closestToZero x y = error "closestToZero: not implemented!"
+closestToZero x y = if abs x < abs y then x else y
 
 
 {- |
@@ -536,8 +538,13 @@ value after "=" where the condition is true.
 
 Casual reminder about adding top-level type signatures for all functions :)
 -}
-
-mid x y z = error "mid: not implemented!"
+mid :: Int -> Int -> Int -> Int
+mid x y z
+    | (x > y && x < z) || (x > z && x < y)  = x
+    | (y > x && y < z) || (y > z && y < x)  = y
+    | x == y || x == z                      = x 
+    | y == z                                = y
+    | otherwise                             = z
 
 {- |
 =⚔️= Task 8
@@ -551,7 +558,10 @@ True
 >>> isVowel 'x'
 False
 -}
-isVowel c = error "isVowel: not implemented!"
+isVowel :: Char -> Bool
+isVowel c
+    | c == 'a' || c == 'e' || c == 'i' || c == 'o' || c == 'u' = True
+    | otherwise = False
 
 
 {- |
@@ -615,8 +625,12 @@ Try to introduce variables in this task (either with let-in or where) to avoid
 specifying complex expressions.
 -}
 
-sumLast2 n = error "sumLast2: Not implemented!"
-
+sumLast2 :: Int -> Int
+sumLast2 n = 
+    let absN            = abs n
+        lastDgt         = lastDigit absN
+        secondToLastDgt = lastDigit (div absN 10)
+        in (lastDgt + secondToLastDgt)
 
 {- |
 =💣= Task 10*
@@ -635,8 +649,12 @@ Implement a function that returns the first digit of a given number.
 You need to use recursion in this task. Feel free to return to it later, if you
 aren't ready for this boss yet!
 -}
-
-firstDigit n = error "firstDigit: Not implemented!"
+firstDigit :: Int -> Int
+firstDigit n
+    | x < 10 = x
+    | otherwise = firstDigit (div x 10)
+  where
+    x = abs n
 
 
 {-