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🎉 chapter1 #572
🎉 chapter1 #572
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@@ -209,31 +209,31 @@ So, the output in this example means that 'False' has type 'Bool'. | |
> Try to guess first and then compare your expectations with GHCi output | ||
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>>> :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 a => a | ||
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A pair of boolean and char: | ||
>>> :t (True, 'x') | ||
<INSERT THE RESULT INSTEAD OF THE TEXT> | ||
(True, 'x') :: (Bool, Char) | ||
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Boolean negation: | ||
>>> :t not | ||
<INSERT THE RESULT INSTEAD OF THE TEXT> | ||
not :: Bool -> Bool | ||
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Boolean 'and' operator: | ||
>>> :t (&&) | ||
<INSERT THE RESULT INSTEAD OF THE TEXT> | ||
(&&) :: Bool -> Bool -> Bool | ||
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Addition of two numbers: | ||
>>> :t (+) | ||
<INSERT THE RESULT INSTEAD OF THE TEXT> | ||
(+) :: Num a => a -> a -> a | ||
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Maximum of two values: | ||
>>> :t max | ||
<INSERT THE RESULT INSTEAD OF THE TEXT> | ||
max :: Ord a => a -> a -> a | ||
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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. | ||
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@@ -301,43 +301,43 @@ expressions in GHCi | |
functions and operators first. Remember this from the previous task? ;) | ||
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>>> 1 + 2 | ||
<INSERT THE RESULT INSTEAD OF THE TEXT> | ||
3 | ||
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>>> 10 - 15 | ||
<INSERT THE RESULT INSTEAD OF THE TEXT> | ||
-5 | ||
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>>> 10 - (-5) -- negative constants require () | ||
<INSERT THE RESULT INSTEAD OF THE TEXT> | ||
15 | ||
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>>> (3 + 5) < 10 | ||
<INSERT THE RESULT INSTEAD OF THE TEXT> | ||
True | ||
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>>> True && False | ||
<INSERT THE RESULT INSTEAD OF THE TEXT> | ||
False | ||
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>>> 10 < 20 || 20 < 5 | ||
<INSERT THE RESULT INSTEAD OF THE TEXT> | ||
True | ||
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>>> 2 ^ 10 -- power | ||
<INSERT THE RESULT INSTEAD OF THE TEXT> | ||
1024 | ||
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>>> not False | ||
<INSERT THE RESULT INSTEAD OF THE TEXT> | ||
True | ||
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>>> div 20 3 -- integral division | ||
<INSERT THE RESULT INSTEAD OF THE TEXT> | ||
6 | ||
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>>> mod 20 3 -- integral division remainder | ||
<INSERT THE RESULT INSTEAD OF THE TEXT> | ||
2 | ||
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>>> max 4 10 | ||
<INSERT THE RESULT INSTEAD OF THE TEXT> | ||
10 | ||
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>>> min 5 (max 1 2) | ||
<INSERT THE RESULT INSTEAD OF THE TEXT> | ||
2 | ||
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>>> max (min 1 10) (min 5 7) | ||
<INSERT THE RESULT INSTEAD OF THE TEXT> | ||
5 | ||
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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 | ||
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@@ -429,6 +429,7 @@ task is to specify the type of this function. | |
49 | ||
-} | ||
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squareSum :: Int -> Int -> Int | ||
squareSum x y = (x + y) * (x + y) | ||
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@@ -449,7 +450,7 @@ 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 | ||
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{- | | ||
After you've implemented the function (or even during the implementation), you | ||
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@@ -490,7 +491,8 @@ Implement a function that returns the last digit of a given number. | |
whether it works for you! | ||
-} | ||
-- DON'T FORGET TO SPECIFY THE TYPE IN HERE | ||
lastDigit n = error "lastDigit: Not implemented!" | ||
lastDigit :: Int -> Int | ||
lastDigit = (`mod` 10) . abs | ||
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{- | | ||
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@@ -520,7 +522,7 @@ 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 | ||
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{- | | ||
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@@ -554,7 +556,11 @@ value after "=" where the condition is true. | |
Casual reminder about adding top-level type signatures for all functions :) | ||
-} | ||
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mid x y z = error "mid: not implemented!" | ||
mid :: Int -> Int -> Int -> Int | ||
mid x y z | ||
| x <= y && y <= z = y | ||
| x >= y && y >= z = y | ||
| otherwise = mid y z x | ||
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{- | | ||
=⚔️= Task 8 | ||
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@@ -568,7 +574,8 @@ True | |
>>> isVowel 'x' | ||
False | ||
-} | ||
isVowel c = error "isVowel: not implemented!" | ||
isVowel :: Char -> Bool | ||
isVowel = (`elem` "aoeiuv") | ||
There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. Nice one! 👍🏼 One note in here, that sometimes, |
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{- | | ||
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@@ -632,7 +639,12 @@ Try to introduce variables in this task (either with let-in or where) to avoid | |
specifying complex expressions. | ||
-} | ||
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sumLast2 n = error "sumLast2: Not implemented!" | ||
sumLast2 :: Int -> Int | ||
sumLast2 x = | ||
let ax = abs x | ||
last = ax `mod` 10 | ||
secondlast = ax `mod` 100 `div` 10 | ||
Comment on lines
+645
to
+646
There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. That is a wonderful solution! 👏🏼 You correctly noticed that it is the Another approach could be also using this: you can see that you use both: mod m 10
div m 10 The standard library has the So you could write it this way: (x, y) = divMod m 10 You can see how we could pattern match on the pair 🙂 |
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in last + secondlast | ||
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{- | | ||
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@@ -653,8 +665,11 @@ You need to use recursion in this task. Feel free to return to it later, if you | |
aren't ready for this boss yet! | ||
-} | ||
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firstDigit n = error "firstDigit: Not implemented!" | ||
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firstDigit :: Int -> Int | ||
firstDigit x | ||
| absx `div` 10 == 0 = absx | ||
| otherwise = firstDigit (absx `div` 10) | ||
where absx = abs x | ||
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{- | ||
You did it! Now it is time to open a pull request with your changes | ||
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That's pretty!
Nice work on using infix form of calling functions! We don't explain this syntax in our course to make it short. But well done 👍