Hey Don,
On Sat, Mar 22, 2008 at 8:39 AM, Don Stewart
I'm not sure how doctest works, or how it would work in a Haskell setting, could you elaborate?
In a nutshell, Python doctest has the programmer put an example "interactive session" in a functions docstring. A doctest module then extracts those, tries running the function on the inputs and sees if it matches the output. Best shown by an example: def adder(a,b): """Returns the sum of the two arguments. >>> adder(10,10) 20 >>> adder("a","b") 'ab' >>> adder(10,"100") Traceback (most recent call last): File "test.py", line 6, in adder return a+b TypeError: unsupported operand type(s) for +: 'int' and 'str' """ return a+b if __name__ == "__main__": import doctest doctest.testmod() # Test this module Running this script with $ python test.py -v gives the following output Trying: adder(10,10) Expecting: 20 ok Trying: adder("a","b") Expecting: 'ab' ok Trying: adder(10,"100") Expecting: Traceback (most recent call last): File "test.py", line 6, in adder return a+b TypeError: unsupported operand type(s) for +: 'int' and 'str' ok 1 items had no tests: __main__ 1 items passed all tests: 3 tests in __main__.adder 3 tests in 2 items. 3 passed and 0 failed. Test passed. I.e it extracted the test cases from the sample interactive session and compared the real results.
One idea that does strike me is that it would be super useful to have the ability in ghci to extract the haddocks associated with a function.
> :doc map
would result in:
-- | 'map' @f xs@ is the list obtained by applying @f@ to each element -- of @xs@, i.e., -- -- > map f [x1, x2, ..., xn] == [f x1, f x2, .. -- > map f [x1, x2, ...] == [f x1, f x2, ...]
marked up in ascii.
I'm not sure if that's related to doctest, but it sure would be useful!
Python does exactly that and it is very very useful. I'd love to see that in GHCi. Arnar