🚀 go-pugleaf

In article <BvBEny.4M8@gabriel.keele.ac.uk>, csa09@seq1.keele.ac.uk (Paul Singleton) writes:
> From article <ALBERTO.92Sep28113506@karna.cs.umd.edu>, by alberto@cs.umd.edu (Jose Alberto Fernandez R):
> 
>> One way to solve this is to use in the code macro commands that
>> expand to the right thing for each system. Assume that your
>> distributed source code is in files with extensions `.pli'. 
>> In your case, the macro definitions look something like this:
>> 
>> 	#ifdef SEPIA
>> 	#define RETRACTALL(x) retract_all(x)
>> 	#else
>> 	#define RETRACTALL(x) retractall(x)
>> 	#endif
>> 
>> and in your code you use the macro RETRACTALL(x):
>> 
>> 	...:- ..., RETRACTALL(foo(X,Y)), ....
>>... 
>> It would be nice if a facility like this would have been provided as
>> part of the language. Then we wouldn't need to borrow tools from 'C'.
> 
> Prolog is a sufficiently wide-spectrum language that we don't need to
> borrow bolt-on programming-in-the-large languages.  I think if we write
> 
> 	retract_all_unit_clause( X) :-
> 		(	dialect( sepia)
> 		->	retract_all( X)
> 		;	dialect( sicstus)
> 		->	retractall( X)
> 		).
> 
> then add either
> 
> 	dialect( sepia).
> or
> 	dialect( sicstus).
> 
> as a fact, and partially evaluate the program, we get the effect of macro
> substitution.  Isn't this a neater way of doing things?  
> ----
>   __   __    Paul Singleton (Mr)           JANET: paul@uk.ac.keele.cs
>  |__) (__    Computer Science Dept.        other: paul@cs.keele.ac.uk
>  |  .  __).  Keele University, Newcastle,    tel: +44 (0)782 621111 x7355
>              Staffs ST5 5BG, ENGLAND         fax: +44 (0)782 713082
Sorry to be on the ignorant side, but what is meant by partial evaluation?