Re: [Chicken-janitors] #1421: problems with building json egg in c5 egg repo

[Chicken Trac]

#1421: problems with building json egg in c5 egg repo
---------------------------------+-----------------
            Reporter:  felix     |      Owner:
                Type:  defect    |     Status:  new
            Priority:  critical  |  Milestone:  5.0
           Component:  expander  |    Version:  5.0
          Resolution:            |   Keywords:
Estimated difficulty:  hard      |
---------------------------------+-----------------

Comment (by sjamaan):

 I believe this is a bug in how packrat works:

 {{{
 (import packrat)

 (define plus-or-minus
   (packrat-parser
    (begin
      (print "here be a define")
      expr)
    (expr ((a <- '+)
           (print "plus: " a))
          ((a <- '-)
           (print "minus: " a)))))
 }}}

 Compiling this with {{{csc -debug 2}}} produces:

 {{{
 [canonicalized]
 (##core#callunit library)

 (##core#callunit eval)

 (##core#undefined)

 (##core#undefined)

 (##core#undefined)

 (chicken.load#load-extension 'packrat '(packrat#) 'require)

 (set! minus
   (let ()
     (let ((expr31 (##core#undefined)))
       (let ((t58 (set! expr31
                    (##core#lambda
                      (results2632)
                      (packrat#results->result
                        results2632
                        'expr
                        (##core#lambda
                          ()
                          (let ((g3334 (packrat#packrat-or
                                         (packrat#packrat-check-base
                                           '+
                                           (##core#lambda
                                             (a42)
                                             (##core#lambda
                                               (results4446)
                                               (packrat#make-result
                                                 (chicken.base#print
 '"plus: " a42)
                                                 results4446))))
                                         (packrat#packrat-check-base
                                           '-
                                           (##core#lambda
                                             (a53)
                                             (##core#lambda
                                               (results5557)
                                               (packrat#make-result
                                                 (chicken.base#print
 '"minus: " a53)
                                                 results5557)))))))
                            (g3334 results2632))))))))
         (let ((t59 (chicken.base#print '"here be a define"))) expr31)))))

 ((##sys#implicit-exit-handler))
 }}}

 As you can see, the expansion of the internal define of json would look
 something like:

 {{{
 (set! parser
   (let ()
      (let (...) ;; parser definitions used by begin
        (let ((t59 (begin (define (white results) ...)))) ... expr))))
 }}}

 This is clearly incorrect: you can't put {{{define}}} in the value
 expression of a let-variable.

--
Ticket URL: <https://bugs.call-cc.org/ticket/1421#comment:1>
CHICKEN Scheme <https://www.call-cc.org/>
CHICKEN Scheme is a compiler for the Scheme programming language.