Re: Compiler with adjustable parsers

> Does anyone know of a compiler/language that allows you to specify changes
> to how the language is parsed (in part at least) from withing the program.


Sure: Prolog allows (re)defining operators. In addition, IBM-Prolog
allows specifying various other syntax items, by changing its scan
tables and its table of "assignable atoms". For example, it allows
the Edinburgh syntax:
a([X|_y],_) :- b(X), !, c(X,_y) .
and, by simply changing these tables and defining different operators,
the default IBM syntax, modified for keyboards without square brackets:
a({X!*y},*) <- b(X) & / & c(X,*y) .


What's more, you can input a clause in one syntax, change the syntax and
then get the clause back in the new syntax (using clause/2 or ax(*,*)).


The parser is quite fast because during processing, all atoms must
be hashed anyway, so comparing against an "assignable atom" is just
a pointer comparison.


- peter ludemann pgl@cup.portal.com [standard disclaimer]

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