Hello,
is ther somebody who also wants to use the packrat egg? To get used to
it, I tried to copy a usage example from
http://www.lshift.net/~tonyg/packrat.pdf . Unfortunately when trying
to copy the text, just garbage text arrives (why?), so I had to type
it again. That's the result:
(require-extension packrat)
;; from 5.2 "A base-generator for a higher-level input stream of
lexemes/tokens
(define (generator tokens)
(let ((stream tokens))
(lambda ()
(if (null? stream)
(values #f #f)
(let ((base-token (car stream)))
(set! stream (cdr stream))
(values #f base-token))))))
;; from 5.3 "A simple calculator"
(define calc
(packrat-parser
expr
(expr ((a <- mulexp '+ b <- mulexp)
(+ a b))
((a <- mulexp) a))
(mulexp (( a <- simple '* b <- simple)
(*a b))
((a <- simple) a))
(simple ((a <- 'num) a)
(('oparen a <- expr 'cparen) a))))
The example is not yet complete (missing: 5.4 An example calculator
session), but I think it should compile already. The issue is, that it
doesn't compile:
| $ csc ./try-packrat.scm
| Warning: literal in operator position: ((quote oparen) a <- expr (quote
cparen))
Or if I apply the interpreter, I get:
| Version 2.5 - linux-unix-gnu-x86-64 - [ 64bit libffi dload ptables applyhook ]
| (c)2000-2006 Felix L. Winkelmann
| ; loading ./try-packrat.scm ...
| ; loading /usr/local/lib/chicken/1/packrat.so ...
| Error: unbound variable: expr
|
| Call history:
|
| <eval> (##sys#require (quote packrat))
| <eval> (packrat-parser expr (expr ((a <- mulexp (quote +) b <-
mulexp) (+ a b)) ((a <- mulexp) a)) (mulexp ((a <- simple (quote...... <--
Any idea? Who else is using packrat?
Regards
Thomas
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