Re: Accessing PowerLoom from Haskell

On 08/28/2015 12:44 AM, Anders N=E5sell wrote:
> 1. Has PowerLoom a C API? I thought it only had C++? That is good news be=
cause my understanding is that Haskell is easier to interface with C than C=
++.
It doesn't have an official C API, but you can "easily" make one =

yourself.  You basically create your own little C-API library using =

extern "C" declarations, compile that in C++ and then link it with your =

C program using the extern "C" names.  For example,something like this =

should work (untested :-)


extern "C" void* pli_s_evaluate(char* command, char* moduleName);

void* pli_s_evaluate(char* command, char* moduleName) {
     return pli::sEvaluate(command, moduleName, NULL);
}

extern "C" char* pli_s_evaluate_to_string(char* command, char* moduleName);

char* s_evaluate_to_string(char* command, char* moduleName) {
     return pli::objectToString(sEvaluate(command, moduleName, NULL));
}


You can either do everything with strings or pass PowerLoom C++ pointers =

as void* and then cast them back where necessary.  I think somebody has =

done this in the past to link PowerLoom into Python, but it's been a =

while and I don't remember if there were any issues.  There could be =

some problems with all the C++ constructor initialization code being run =

when your C or Haskell program starts up, but that should be solvable.

Anyway, I am sorry this isn't better supported directly from PowerLoom =

(yet), it's one of the many things on the never ending TO DO list.

Hans