Bug in est/Test/Chapter1.hs ? about learn4haskell

[twolodzko]

OK, now I understood what you meant.

[vrom911]

Hey @twolodzko ! I think that you defined lastDigit as:

lastDigit :: Integer -> Integer

while

firstDigit :: Int -> Int

It is better to have consistent types here 🙂
Hope it helps!

[twolodzko]

@vrom911 thanks, but I also tried using Integer instead and I still get

test/Test/Chapter1.hs:72:14: error:
    • Couldn't match expected type ‘Int’ with actual type ‘Integer’
    • In the first argument of ‘(===)’, namely ‘(firstDigit x :: Int)’
      In a stmt of a 'do' block:
        (firstDigit x :: Int) === (lastDigit (reverseInt x) :: Int)
      In the second argument of ‘($)’, namely
        ‘do x <- forAll $ Gen.int (Range.linear (- 200) 200)
            (firstDigit x :: Int) === (lastDigit (reverseInt x) :: Int)’
   |
72 |             (firstDigit x :: Int) === (lastDigit (reverseInt x) :: Int)
   |              ^^^^^^^^^^^^

test/Test/Chapter1.hs:72:25: error:
    • Couldn't match expected type ‘Integer’ with actual type ‘Int’
    • In the first argument of ‘firstDigit’, namely ‘x’
      In the first argument of ‘(===)’, namely ‘(firstDigit x :: Int)’
      In a stmt of a 'do' block:
        (firstDigit x :: Int) === (lastDigit (reverseInt x) :: Int)
   |
72 |             (firstDigit x :: Int) === (lastDigit (reverseInt x) :: Int)
   |                         ^

test/Test/Chapter1.hs:72:40: error:
    • Couldn't match expected type ‘Int’ with actual type ‘Integer’
    • In the second argument of ‘(===)’, namely
        ‘(lastDigit (reverseInt x) :: Int)’
      In a stmt of a 'do' block:
        (firstDigit x :: Int) === (lastDigit (reverseInt x) :: Int)
      In the second argument of ‘($)’, namely
        ‘do x <- forAll $ Gen.int (Range.linear (- 200) 200)
            (firstDigit x :: Int) === (lastDigit (reverseInt x) :: Int)’
   |
72 |             (firstDigit x :: Int) === (lastDigit (reverseInt x) :: Int)
   |                                        ^^^^^^^^^^^^^^^^^^^^^^^^

test/Test/Chapter1.hs:72:51: error:
    • Couldn't match expected type ‘Integer’ with actual type ‘Int’
    • In the first argument of ‘lastDigit’, namely ‘(reverseInt x)’
      In the second argument of ‘(===)’, namely
        ‘(lastDigit (reverseInt x) :: Int)’
      In a stmt of a 'do' block:
        (firstDigit x :: Int) === (lastDigit (reverseInt x) :: Int)
   |
72 |             (firstDigit x :: Int) === (lastDigit (reverseInt x) :: Int)
   |                                                   ^^^^^^^^^^^^
make: *** [Makefile:12: test-chapter1] Error 1