[mercury-users] Higher-order calls from foreign code

[Ralph Becket]

Peter Hawkins, Wednesday,  3 August 2005:
> Hi...
> 
> Is there a direct way to make a higher order call from foreign code? I 
> have an MR_Word which contains the address of a closure which takes no 
> arguments and is semidet, and I'd like to call it.

Not directly that I know of, but you could do something like this (see
http://www.mercury.cs.mu.oz.au/information/doc-latest/mercury_ref/Calling-Mercury-code-from-C.html#Calling%20Mercury%20code%20from%20C)

:- pragma export(invoke_closure(in((pred) is semidet)),
	"invoke_closure").

:- pred invoke_closure((pred)::in((pred) is semidet)) is semidet.

invoke_closure(P) :-
	P.

and then you can write `invoke_closure(P)' directly in your C code.

-- Ralph
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