Re: syncase code issue 1.8.8 -> 2.0.11

[Panicz Maciej Godek <godek.maciek@gmail.com>]

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2014-09-18 3:18 GMT+02:00 Matt Wette <mwette@alumni.caltech.edu>:

> Hi Folks,
>
> Anyone interested in looking at my syntax-case code?   I wrote this
> several years ago under 1.8.8.  Now moving to 2.0.11: not working :(.
>
> Matt
>
>

> [...]
> In 1.8.8, I get the above output.   In 2.0.11 I get
>
> Syntax-case macros are now a part of Guile core; importing (ice-9 syncase)
> is no longer necessary.   <=(no issue here)
> ice-9/psyntax.scm:1274:12: In procedure dobody:
> ice-9/psyntax.scm:1274:12: Syntax error:
> u1.scm:106:18: definition in expression context, where definitions are not
> allowed


I haven't time to look at your code more closely, but the error message is
quite informative here: clearly the usage of your macro introduces a
definition in expression context, which doesn't conform to the Scheme
specification. It seems that guile 1.8 treated definitions like
expressions, but it is no longer the case.

Apparently, your code expands to a series of definitions. Therefore the
invocation

(format #t "~a\n" (define-tokenizer tokiz ("[0-9]+" #\1) ("[a-z]+" #\a)))

makes no sense (e.g. because "define-tokenizer" produces no value, that
should be passed to format, and after expansion it contains no expression
that could be evaluated), and neither does

(format #t "~a\n" (define mt (make-tokiz "abc=def")))

I don't know what was your intention in the first case, but you could
rearrange the second line in the following way:

(define mt (make-tokiz "abc=def"))
(format #t "~a\n" mt)

The first line could simply be replaced with the sole definition, i.e.
(define-tokenizer tokiz ("[0-9]+" #\1) ("[a-z]+" #\a))

(I am guessing that the invocation from within "format" stems from
debugging)

regards

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