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change model reader to coerce a syntax #:language result to a datum for 'read' mode

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svn: r16292
This commit is contained in:
Matthew Flatt 2009-10-09 20:30:05 +00:00
parent 32eb932858
commit 56fbafa6c8
2 changed files with 9 additions and 4 deletions
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5
collects/syntax/module-reader.ss
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@ -69,7 +69,10 @@
[w1 #,~wrapper1]
[w2 #,~wrapper2]
[whole? #,~whole-body-readers?]
[rd (lambda (in) (wrap-internal lang in read whole? w1 stx?
[rd (lambda (in) (wrap-internal (if (and (not stx?) (syntax? lang))
(syntax->datum lang)
lang)
in read whole? w1 stx?
modpath src line col pos))]
[r (cond [(not w2) (rd in)]
[(ar? w2 3) (w2 in rd stx?)]

8
collects/syntax/scribblings/module-reader.scrbl
View File

@ -190,10 +190,12 @@ expression can be useful in cases such as the above, where the base
language module is chosen based on the input. To make this more
convenient, you can omit the @scheme[module-path] and instead specify
it via a @scheme[#:language] expression. This expression can evaluate
to a datum which is used as a language, or it can evaluate to a thunk.
In the latter case, the thunk will be invoked to return such a datum
to a datum or syntax object that is used as a language, or it can evaluate to a thunk.
In the latter case, the thunk is invoked to obtain such a datum
before reading the module body begins, in a dynamic extent where
@scheme[current-input-port] is the source input. Using this, the last
@scheme[current-input-port] is the source input. A syntax object is converted
using @scheme[syntax->datum] when a datum is needed (for @scheme[read] instead of @scheme[read-syntax]).
Using @scheme[#:language], the last
example above can be written more concisely:
@schemeblock[
(module reader syntax/module-reader