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clarified term-match vs term-let a little bit

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svn: r12957
This commit is contained in:
Robby Findler 2008-12-31 02:19:30 +00:00
parent 5cefde5945
commit 459a3247e7
1 changed files with 14 additions and 0 deletions
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collects/redex/redex.scrbl
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@ -450,6 +450,12 @@ recursively matches the corresponding list element. There
may be a single ellipsis in any list pattern; if one is may be a single ellipsis in any list pattern; if one is
present, the pattern before the ellipses may match multiple present, the pattern before the ellipses may match multiple
adjacent elements in the list value (possibly none). adjacent elements in the list value (possibly none).
This form is a lower-level form in Redex, and not really designed to
be used directly. If you want a @scheme[let]-like form that uses
Redex's full pattern matching facilities, see @scheme[term-match] and
@scheme[term-match/single].
} }
@defform[(term-match language [#, @|ttpattern| expression] ...)]{ @defform[(term-match language [#, @|ttpattern| expression] ...)]{
@ -460,6 +466,10 @@ function returns a list of the values of the expression
where the pattern matches. If one of the patterns matches where the pattern matches. If one of the patterns matches
multiple times, the expression is evaluated multiple times, multiple times, the expression is evaluated multiple times,
once with the bindings in the pattern for each match. once with the bindings in the pattern for each match.
When evaluating a @scheme[term-match] expression, the patterns are
compiled in an effort to speed up matching. Using the procedural
result multiple times to avoid compiling the patterns multiple times.
} }
@defform[(term-match/single language [#, @|ttpattern| expression] ...)]{ @defform[(term-match/single language [#, @|ttpattern| expression] ...)]{
@ -472,6 +482,10 @@ is signaled. If no patterns match, an error is signaled.
Raises an exception recognized by @scheme[exn:fail:redex?] if Raises an exception recognized by @scheme[exn:fail:redex?] if
no clauses match or if one of the clauses matches multiple ways. no clauses match or if one of the clauses matches multiple ways.
When evaluating a @scheme[term-match/single] expression, the patterns
are compiled in an effort to speed up matching. Using the procedural
result multiple times to avoid compiling the patterns multiple times.
} }
@defproc[(plug [context any?] [expression any?]) any]{ @defproc[(plug [context any?] [expression any?]) any]{