[Haskell-beginners] Re: Compiling C into Haskell

[Heinrich Apfelmus]

Brent Yorgey wrote:
> Hein Hundal wrote:
>> 
>> I was hoping the C-Haskell mix would work.  I am glad to hear that
>> you have good things to say about it.
>> 
>> My main reason for thinking about the C-to-Haskell compiler was to
>> address the question "Say you had a C program.  Can you always
>> convert it to Haskell in such a way that the compiled Haskell is
>> not too slow and does not need too much memory?"  Supposing that
>> too slow means slower than 1/4 the speed of C and too much memory
>> means twice the memory of C.
>> 
>> Do you know the answer to this question?
> 
> My guess is that the answer is technically "no".  If I recall 
> correctly, there are some imperative data structures where the best 
> known time complexity for a functional version is worse than the 
> imperative version by a factor of (log n), so in that case you 
> wouldn't be able to stay within a constant factor of C.

Well, you can always fall back to arrays in the ST monad...

> However, I think in practice the answer is usually "yes"; but it
> might be hard to do it via a mechanical compilation. Idiomatic (and
> fast) Haskell is often organized very differently than corresponding
> C code.

If you already have a C program, then it's probably easiest to link it
in with the Foreign Function Interface.


Regards,
Heinrich Apfelmus

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