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🎉 chapter1 #572
🎉 chapter1 #572
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@@ -209,31 +209,31 @@ | |
> 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 @@ | |
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) | ||
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2 | ||
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>>> max (min 1 10) (min 5 7) | ||
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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 @@ | |
49 | ||
-} | ||
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squareSum :: Int -> Int -> Int | ||
squareSum x y = (x + y) * (x + y) | ||
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@@ -449,7 +450,7 @@ | |
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 @@ | |
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 @@ | |
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 @@ | |
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 @@ | |
>>> 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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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 | ||
Check warning on line 645 in src/Chapter1.hs GitHub Actions / Chapter One (3.8, 9.4.4)
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secondlast = ax `mod` 100 `div` 10 | ||
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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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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 | ||
| x `div` 10 == 0 = x | ||
| otherwise = firstDigit (x `div` 10) | ||
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. I see, that for a negative numbers it will be not return the correct answer. Sometimes it is tricky to keep in mind all the edge cases, so no worries, but the idea and recursive solution is awesome 👏🏼 |
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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 👍