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update R6RS incompatibilities

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* doc/ref/r6rs.texi (R6RS Incompatibilities): Update.
This commit is contained in:
Andy Wingo 2011-02-27 13:07:04 +01:00
parent 4335366389
commit 450aee6790
1 changed files with 25 additions and 24 deletions
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49
doc/ref/r6rs.texi
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@ -38,9 +38,11 @@ does not restore it. This is a bug.
@item
R6RS unicode escapes within strings are disabled by default, because
they conflict with Guile's already-existing escapes. R6RS behavior can
be turned on via a reader option. @xref{String Syntax}, for more
information.
they conflict with Guile's already-existing escapes. The same is the
case for R6RS treatment of escaped newlines in strings.
R6RS behavior can be turned on via a reader option. @xref{String
Syntax}, for more information.
@item
A @code{set!} to a variable transformer may only expand to an
@ -51,23 +53,8 @@ expression was in definition context.
Instead of using the algorithm detailed in chapter 10 of the R6RS,
expansion of toplevel forms happens sequentially.
For example, while the expansion of the following set of recursive
nested definitions does do the correct thing:
@example
(let ()
(define even?
(lambda (x)
(or (= x 0) (odd? (- x 1)))))
(define-syntax odd?
(syntax-rules ()
((odd? x) (not (even? x)))))
(even? 10))
@result{} #t
@end example
@noindent
The same definitions at the toplevel do not:
For example, while the expansion of the following set of toplevel
definitions does the correct thing:
@example
(begin
@ -78,6 +65,20 @@ The same definitions at the toplevel do not:
(syntax-rules ()
((odd? x) (not (even? x)))))
(even? 10))
@result{} #t
@end example
@noindent
The same definitions outside of the @code{begin} wrapper do not:
@example
(define even?
(lambda (x)
(or (= x 0) (odd? (- x 1)))))
(define-syntax odd?
(syntax-rules ()
((odd? x) (not (even? x)))))
(even? 10)
<unnamed port>:4:18: In procedure even?:
<unnamed port>:4:18: Wrong type to apply: #<syntax-transformer odd?>
@end example
@ -86,10 +87,10 @@ This is because when expanding the right-hand-side of @code{even?}, the
reference to @code{odd?} is not yet marked as a syntax transformer, so
it is assumed to be a function.
While it is likely that we can fix the case of toplevel forms nested in
a @code{begin} or a @code{library} form, a fix for toplevel programs
seems trickier to implement in a backward-compatible way. Suggestions
and/or patches would be appreciated.
This bug will only affect top-level programs, not code in @code{library}
forms. Fixing it for toplevel forms seems doable, but tricky to
implement in a backward-compatible way. Suggestions and/or patches would
be appreciated.
@item
The @code{(rnrs io ports)} module is mostly unimplemented. Work is