fjh at cs.mu.oz.au
Fri Sep 26 14:08:57 AEST 1997
Tomas By, you wrote:
> In general, if I have a procedure with several modes, eg:
> :- pred stream_tree(stream(T),tree(T)).
> :- mode stream_tree(in,out) is det.
> :- mode stream_tree(out,in) is det.
> but I can't use the same code for both modes, how do I write
> the "top-level"?
The way to do this is to pass a argument specifying the direction:
:- type direction ---> forward ; backward.
:- inst forward ---> forward.
:- inst backward ---> backward.
:- pred stream_tree(direction,stream(T),tree(T)).
:- mode stream_tree(in(forward),in,out) is det.
:- mode stream_tree(in(backward),out,in) is det.
stream_tree(forward, Stream, Tree) :-
... code for the (in, out) mode ...
stream_tree(backward, Stream, Tree) :-
... code for the (out, in) mode ...
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