Re: syntax-local-value patch for discussion

[Stefan Israelsson Tampe <stefan.itampe@gmail.com>]

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Hi,

Working on porting syntax-parse is a learning experience and I know
understand how it uses
syntax-local-value as a way to lookup a syntax object by joining the wraps
together with the
total wrap at the macro call.

The question is if this really are the total wrap e.g. contains the history
of all the previous variable
and macro and syntax definitions. Is this so or are it a partial part of
the history?

Anyway syntax-parse works by defining pattern variables the hard core way
and I have now changed that
to a more standard way of implementation leading to skipping
syntax-local-value (variables are stored in
a struct and they does then not contain the correct wrap) but instead
examine the syntax variables used
and transport the wraps of the containing syntax variable of the struct.
For this I have a messy and sloppy
algorithm just to make it work - but I would like to have a syntax-join
function that takes two syntax objects
and join them correctly and robustly in the pressense of eventual marks or
not.

Anyway this now works,

(define-syntax-class t (pattern (x:id y)))
(define-syntax a (lambda (x) (syntax-parse x ((_ z:t ...) #'(+ z.y ...)))))
(a (x1 1) (x2 2) (x3 3))
$1 = 6

/Stefan

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