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macro documentation fixup

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* doc/ref/api-macros.texi: make the difference between pattern variables
  and lexical variables a bit clearer.
This commit is contained in:
Noah Lavine 2011-02-02 09:52:10 -05:00 • committed by Andy Wingo
parent 71d0152e66
commit 09cb3ae237
1 changed files with 8 additions and 5 deletions
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13
doc/ref/api-macros.texi
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@ -574,11 +574,14 @@ Here's another solution that doesn't work:
(if it then else))))))) (if it then else)))))))
@end example @end example
The reason that this one doesn't work is that there are really two environments The reason that this one doesn't work is that there are really two
at work here -- the environment of pattern variables, as bound by environments at work here -- the environment of pattern variables, as
@code{syntax-case}, and the environment of lexical variables, as bound by normal bound by @code{syntax-case}, and the environment of lexical variables,
Scheme. Here we need to introduce a piece of Scheme's environment into that of as bound by normal Scheme. The outer let form establishes a binding in
the syntax expander, and we can do so using @code{syntax-case} itself: the environment of lexical variables, but the inner let form is inside a
syntax form, where only pattern variables will be substituted. Here we
need to introduce a piece of the lexical environment into the pattern
variable environment, and we can do so using @code{syntax-case} itself:
@example @example
;; works, but is obtuse ;; works, but is obtuse