On Mon 28 Mar 2011 22:44, Noah Lavine <noah.b.lav...@gmail.com> writes:
> - say that string PEGs can only occur at the top level of a PEG
> expression. The peg module has never been released, so no one uses
> this feature now anyway.
> - instead of defining a new function peg-extended-compile, redefine
> peg-sexp-compile via set! once we have string pegs.
> - write peg-extended-compile as its own big case statement, basically
> duplicating peg-sexp-compile.
> - adopt some interface that allows people to extend the cases in
> peg-sexp-compile. We would start with just s-expression PEGs, then use
> this interface to add string PEGs later in the load sequence.
This last is the best. What if we define a module that serves as a
registry of PEG match behaviors, like `(ice-9 peg matchers)'. Then we
define `define-peg-matcher' or something, so that we can:
(define-peg-matcher and cg-and)
where define-peg-matcher is
(define-syntax define-peg-matcher
(syntax-rules ()
((_ name binding)
(module-define! (resolve-module '(ice-9 peg matchers))
'name
binding))))
Then instead of defining separate cases for ignore, range, etc the
peg-sexp-compile macro does:
((matcher arg ...) (identifier? #'matcher)
((module-ref (resolve-module '(ice-9 peg matchers))
(syntax->datum #'matcher))
#'(arg ...)
mode))
Then the peg-string module registers a matcher for `peg'.
Dunno. WDYT?
Andy
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