solve Lecture1

src/Lecture1.hs

@@ -39,6 +39,7 @@ module Lecture1
 its behaviour, possible types for the function arguments and write the
 type signature explicitly.
 -}
+makeSnippet :: Int -> [Char] -> [Char]
 makeSnippet limit text = take limit ("Description: " ++ text) ++ "..."
 
 {- | Implement a function that takes two numbers and finds sum of
@@ -54,7 +55,8 @@ Explanation: @sumOfSquares 3 4@ should be equal to @9 + 16@ and this
 is 25.
 -}
 -- DON'T FORGET TO SPECIFY THE TYPE IN HERE
-sumOfSquares x y = error "TODO!"
+sumOfSquares :: Num a => a -> a -> a
+sumOfSquares x y = x * x + y * y
 
 {- | Implement a function that returns the last digit of a given number.
 
@@ -67,7 +69,9 @@ sumOfSquares x y = error "TODO!"
 
 -}
 -- DON'T FORGET TO SPECIFY THE TYPE IN HERE
-lastDigit n = error "lastDigit: Not implemented!"
+lastDigit :: Integral a => a -> a
+lastDigit n =
+    mod (abs n) 10
 
 {- | Write a function that takes three numbers and returns the
 difference between the biggest number and the smallest one.
@@ -81,7 +85,11 @@ and 1 is the smallest, and 7 - 1 = 6.
 Try to use local variables (either let-in or where) to implement this
 function.
 -}
-minmax x y z = error "TODO"
+minmax :: (Num a, Ord a) => a -> a -> a -> a
+minmax x y z =
+    let biggest = maximum [x,y,z]
+        smallest = minimum [x,y,z]
+    in biggest - smallest
 
 {- | Implement a function that takes a string, start and end positions
 and returns a substring of a given string from the start position to
@@ -98,7 +106,11 @@ start position can be considered as zero (e.g. substring from the
 first character) and negative end position should result in an empty
 string.
 -}
-subString start end str = error "TODO"
+subString :: Int -> Int -> [Char] -> [Char]
+subString start end str
+    | end < 0 || start > end = ""
+    | start <= 0 = take (end + 1) str
+    | otherwise = drop start (take (end+1) str)
 
 {- | Write a function that takes a String — space separated numbers,
 and finds a sum of the numbers inside this string.
@@ -108,7 +120,9 @@ and finds a sum of the numbers inside this string.
 
 The string contains only spaces and/or numbers.
 -}
-strSum str = error "TODO"
+strSum :: (Num a, Read a) => String -> a
+strSum str =
+    sum (map read (words str))
 
 {- | Write a function that takes a number and a list of numbers and
 returns a string, saying how many elements of the list are strictly
@@ -123,4 +137,17 @@ and lower than 6 elements (4, 5, 6, 7, 8 and 9).
 
 🕯 HINT: Use recursion to implement this function.
 -}
-lowerAndGreater n list = error "TODO"
+lowerAndGreater :: (Show a, Ord a) => a -> [a] -> [Char]
+lowerAndGreater n list =
+        iter n list 0 0
+        where
+            iter n [] lower greater = show n
+                                      ++ " is greater than "
+                                      ++ show lower
+                                      ++ " elements and lower than "
+                                      ++ show greater
+                                      ++ " elements"
+            iter n (h:t) lower greater
+                | h < n = iter n t (lower + 1) greater
+                | h > n = iter n t lower (greater + 1)
+                | otherwise = iter n t lower greater