[Haskell-cafe] Poor libraries documentation

[Jonathan Cast]

On 30 Jan 2008, at 7:19 PM, Anton van Straaten wrote:

> Derek Elkins wrote:
>> On Thu, 2008-01-31 at 02:18 +0000, Neil Mitchell wrote:
> ...
>>> It isn't something that would throw a C programmer off, but it is
>>> something that could confuse a pure Haskell programmer. And the only
>>> way I could be sure of radians versus degrees was by trying it out,
>>> not a great strategy for determining the implementation of  
>>> functions!
>> Uh, why not?  Often that's exactly what I do as checking even
>> conveniently located documentation is more time consuming than just
>> trying it.
>
> I agree, but at the risk of veering uncharacteristically off-topic  
> for haskell-cafe, I think it's an interesting example of the degree  
> of assurance about correctness we're willing to accept in practice,  
> in real development.
>
> We discover a function called, say, "cos", probably by guessing  
> it's name, run a very small number of simple tests on it, see the  
> answers we expect, and decide that it's the function we want.

True enough; more complicated tests seem to reveal the opposite  
conclusion:

 > quickCheck $ \ x -> cos (x + 2*pi) == cos x
Falsifiable, after 2 tests:
-1.0

jcc