[Haskell-cafe] Signature for non-empty filter

[Bulat Ziganshin]

Hello Henning,

Thursday, February 7, 2008, 12:29:02 AM, you wrote:

>> it's impossible to check for *arbitrary* function call whether it will be
>> terminated. seems that you don't have formal CS education? :)
>>
>> so one can develop set of functions that are guaranteed to be
>> terminated or guaranteed to be non-trivial. but it's impossible to
>> check for arbitrary function whether it's trivial and even whether it
>> will terminate for particular data

> If the type checker does not terminate because the checked function does
> not terminate on the example input, then the function does not pass the
> type check and as a compromise this would be ok.

how you can check that some code doesn't terminate? ;)  it may be just
a bit too slow. we again return to my original point - we can check
for *some* representations of trivial functions values, but we can't
*ensure* that some computation is non-trivial


-- 
Best regards,
 Bulat                            mailto:Bulat.Ziganshin at gmail.com