[+] Chapter1

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 +296,44 @@ expressions in GHCi
   functions and operators first. Remember this from the previous task? ;)
 
 >>> 1 + 2
-INSERT THE RESULT INSTEAD OF THE TEXT
+3
+it :: Num a => a
 >>> 10 - 15
-
+-5
+it :: Num a => a
 >>> 10 - (-5)  -- negative constants require ()
-
+15
+it :: Num a => a
 >>> (3 + 5) < 10
-
+True
+it :: Bool
 >>> True && False
-
+False
+it :: Bool
 >>> 10 < 20 || 20 < 5
-
+True
+it :: Bool
 >>> 2 ^ 10  -- power
-
+1024
+it :: Num a => a
 >>> not False
-
+True
+it :: Bool
 >>> div 20 3  -- integral division
-
+6
+it :: Integral a => a
 >>> mod 20 3  -- integral division remainder
-
+2
+it :: Integral a => a
 >>> max 4 10
-
+10
+it :: (Ord a, Num a) => a
 >>> min 5 (max 1 2)
-
+2
+it :: (Ord a, Num a) => a
 >>> max (min 1 10) (min 5 7)
-
+5
+it :: (Ord a, Num a) => a
 
 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
@@ -411,7 +424,7 @@ task is to specify the type of this function.
 >>> squareSum 3 4
 49
 -}
-
+squareSum :: Int -> Int -> Int
 squareSum x y = (x + y) * (x + y)
 
 
@@ -432,7 +445,7 @@ 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 +485,8 @@ 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 n 10
 
 
 {- |
@@ -503,7 +516,7 @@ 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 = min (abs x) (abs y)
 
 
 {- |
@@ -536,8 +549,8 @@ 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 = max (min x  y) (min (max x y) z)
 
 {- |
 =⚔️= Task 8
@@ -551,8 +564,13 @@ True
 >>> isVowel 'x'
 False
 -}
-isVowel c = error "isVowel: not implemented!"
-
+isVowel c
+  | c == 'a' = True
+  | c == 'e' = True
+  | c == 'i' = True
+  | c == 'o' = True
+  | c == 'u' = True
+  | otherwise = False
 
 {- |
 == Local variables and functions
@@ -615,8 +633,12 @@ 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 n = first n + second n
+  where
+    first :: Int -> Int
+    first n = mod n 10
+    second :: Int -> Int
+    second n = mod (div n 10) 10
 
 {- |
 =💣= Task 10*
@@ -635,8 +657,10 @@ 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
+  | n < 10 = n
+  | otherwise = firstDigit $ div n 10
 
 
 {-