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From: jiyang@ecrcvax.UUCP (Jiyang Xu)
Newsgroups: comp.lang.prolog
Subject: Re: Bootstrapping precedence grammars.
Summary: Implement read(X) in Prolog
Message-ID: <752@ecrcvax.UUCP>
Date: 4 Aug 89 08:21:23 GMT
References: <3635@csd4.milw.wisc.edu>
Organization: ECRC, Munich 81, West Germany
Lines: 19

In article <3635@csd4.milw.wisc.edu>, markh@csd4.milw.wisc.edu (Mark William Hopkins) writes:
>    Can Prolog's read(X) predicate be defined using only the character
> predicates for I/O?  In other words, does Prolog have the capacity to
> bootstrap its own precedence grammar, using the operator declarations
> made by the op predicate?

Certainly you can, as defined in the famous O'Keefe's reader, which
is also used in SB-Prolog and possibly many other Prologs.
                                                                      
>                          op(Prec, Type, Rator)
>
> cannot be used in the mode
> 
> 			 op(OUTPUT, OUTPUT, INPUT),
                                                                   
There is another predicate "current_op/3" for this purpose.
The predicate is implemented in most Prolog systems.