643 lines
27 KiB
Racket
643 lines
27 KiB
Racket
#lang scribble/doc
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@(require scribble/bnf
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"mz.ss"
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"rx.ss")
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@title[#:tag "regexp"]{Regular Expressions}
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@section-index{regexps}
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@section-index{pattern matching}
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@section-index["strings" "pattern matching"]
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@section-index["input ports" "pattern matching"]
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@local-table-of-contents[]
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Regular expressions are specified as strings or byte strings, using
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the same pattern language as the Unix utility @exec{egrep} or Perl. A
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string-specified pattern produces a character regexp matcher, and a
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byte-string pattern produces a byte regexp matcher. If a character
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regexp is used with a byte string or input port, it matches UTF-8
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encodings (see @secref["encodings"]) of matching character streams;
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if a byte regexp is used with a character string, it matches bytes in
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the UTF-8 encoding of the string.
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Regular expressions can be compiled into a @defterm{regexp value} for
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repeated matches. The @scheme[regexp] and @scheme[byte-regexp]
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procedures convert a string or byte string (respectively) into a
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regexp value using one syntax of regular expressions that is most
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compatible to @exec{egrep}. The @scheme[pregexp] and
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@scheme[byte-pregexp] procedures produce a regexp value using a
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slightly different syntax of regular expressions that is more
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compatible with Perl. In addition, Scheme constants written with
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@litchar{#rx} or @litchar{#px} (see @secref["reader"]) produce
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compiled regexp values.
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The internal size of a regexp value is limited to 32 kilobytes; this
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limit roughly corresponds to a source string with 32,000 literal
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characters or 5,000 operators.
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@;------------------------------------------------------------------------
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@section[#:tag "regexp-syntax"]{Regexp Syntax}
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The following syntax specifications describe the content of a string
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that represents a regular expression. The syntax of the corresponding
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string may involve extra escape characters. For example, the regular
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expression @litchar["(.*)\\1"] can be represented with the string
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@scheme["(.*)\\1"] or the regexp constant @scheme[#rx"(.*)\\1"]; the
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@litchar["\\"] in the regular expression must be escaped to include it
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in a string or regexp constant.
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The @scheme[regexp] and @scheme[pregexp] syntaxes share a common core:
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@common-table
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The following completes the grammar for @scheme[regexp], which treats
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@litchar["{"] and @litchar["}"] as literals, @litchar["\\"] as a
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literal within ranges, and @litchar["\\"] as a literal producer
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outside of ranges.
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@rx-table
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The following completes the grammar for @scheme[pregexp], which uses
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@litchar["{"] and @litchar["}"] bounded repetition and uses
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@litchar["\\"] for meta-characters both inside and outside of ranges.
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@px-table
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@;------------------------------------------------------------------------
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@section{Additional Syntactic Constraints}
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In addition to matching a grammars, regular expressions must meet two
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syntactic restrictions:
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@itemize{
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@item{In a @nonterm{repeat} other than @nonterm{atom}@litchar{?},
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then @nonterm{atom} must not match an empty sequence.}
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@item{In a @litchar{(?<=}@nonterm{regexp}@litchar{)} or
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@litchar{(?<!}@nonterm{regexp}@litchar{)},
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the @nonterm{regexp} must match a bounded sequence, only.}
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}
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These contraints are checked syntactically by the following type
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system. A type [@math{n}, @math{m}] corresponds to an expression that
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matches between @math{n} and @math{m} characters. In the rule for
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@litchar{(}@nonterm{Regexp}@litchar{)}, @math{N} means the number such
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that the opening parenthesis is the @math{N}th opening parenthesis for
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collecting match reports. Non-emptiness is inferred for a
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backreference pattern, @litchar["\\"]@nonterm{N}, so that a
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backreference can be used for repetition patterns; in the case of
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mutual dependencies among backreferences, the inference chooses the
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fixpoint that maximizes non-emptiness. Finiteness is not inferred for
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backreferences (i.e., a backreference is assumed to match an
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arbitrarily large sequence).
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@type-table
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@;------------------------------------------------------------------------
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@section{Regexp Constructors}
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@defproc[(regexp? [v any/c]) boolean?]{
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Returns @scheme[#t] if @scheme[v] is a regexp value created by
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@scheme[regexp] or @scheme[pregexp], @scheme[#f] otherwise.}
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@defproc[(pregexp? [v any/c]) boolean?]{
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Returns @scheme[#t] if @scheme[v] is a regexp value created by
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@scheme[pregexp] (not @scheme[regexp]), @scheme[#f] otherwise.}
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@defproc[(byte-regexp? [v any/c]) boolean?]{
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Returns @scheme[#t] if @scheme[v] is a regexp value created by
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@scheme[byte-regexp] or @scheme[byte-pregexp], @scheme[#f] otherwise.}
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@defproc[(byte-pregexp? [v any/c]) boolean?]{
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Returns @scheme[#t] if @scheme[v] is a regexp value created by
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@scheme[byte-pregexp] (not @scheme[byte-regexp]), @scheme[#f]
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otherwise.}
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@defproc[(regexp [str string?]) regexp?]{
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Takes a string representation of a regular expression (using the
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syntax in @secref["regexp-syntax"]) and compiles it into a regexp
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value. Other regular expression procedures accept either a string or a
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regexp value as the matching pattern. If a regular expression string
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is used multiple times, it is faster to compile the string once to a
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regexp value and use it for repeated matches instead of using the
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string each time.
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The @scheme[object-name] procedure returns
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the source string for a regexp value.
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@examples[
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(regexp "ap*le")
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(object-name #rx"ap*le")
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]}
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@defproc[(pregexp [string string?]) pregexp?]{
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Like @scheme[regexp], except that it uses a slightly different syntax
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(see @secref["regexp-syntax"]). The result can be used with
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@scheme[regexp-match], etc., just like the result from
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@scheme[regexp].
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@examples[
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(pregexp "ap*le")
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(regexp? #px"ap*le")
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]}
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@defproc[(byte-regexp [bstr bytes?]) byte-regexp?]{
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Takes a byte-string representation of a regular expression (using the
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syntax in @secref["regexp-syntax"]) and compiles it into a
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byte-regexp value.
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The @scheme[object-name] procedure
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returns the source byte string for a regexp value.
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@examples[
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(byte-regexp #"ap*le")
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(object-name #rx#"ap*le")
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(byte-regexp "ap*le")
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]}
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@defproc[(byte-pregexp [bstr bytes?]) byte-pregexp?]{
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Like @scheme[byte-regexp], except that it uses a slightly different
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syntax (see @secref["regexp-syntax"]). The result can be used with
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@scheme[regexp-match], etc., just like the result from
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@scheme[byte-regexp].
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@examples[
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(byte-pregexp #"ap*le")
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]}
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@defproc*[([(regexp-quote [str string?] [case-sensitive? any/c #t]) string?]
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[(regexp-quote [bstr bytes?] [case-sensitive? any/c #t]) bytes?])]{
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Produces a string or byte string suitable for use with @scheme[regexp]
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to match the literal sequence of characters in @scheme[str] or
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sequence of bytes in @scheme[bstr]. If @scheme[case-sensitive?] is
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true, the resulting regexp matches letters in @scheme[str] or
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@scheme[bytes] case-insensitively, otherwise it matches
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case-sensitively.
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@examples[
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(regexp-match "." "apple.scm")
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(regexp-match (regexp-quote ".") "apple.scm")
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]}
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@;------------------------------------------------------------------------
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@section{Regexp Matching}
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@defproc[(regexp-match [pattern (or/c string? bytes? regexp? byte-regexp?)]
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[input (or/c string? bytes? input-port?)]
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[start-pos nonnegative-exact-integer? 0]
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[end-pos (or/c nonnegative-exact-integer? false/c) #f]
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[output-port (or/c output-port? false/c) #f])
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(or/c (listof (or/c (cons (or/c string? bytes?)
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(or/c string? bytes?))
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false/c))
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false/c)]{
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Attempts to match @scheme[pattern] (a string, byte string, regexp
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value, or byte-regexp value) once to a portion of @scheme[input]. The
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matcher finds a portion of @scheme[input] that matches and is closest
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to the start of the input (after @scheme[start-pos]).
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The optional @scheme[start-pos] and @scheme[end-pos] arguments select
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a portion of @scheme[input] for matching; the default is the entire
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string or the stream up to an end-of-file. When @scheme[input] is a
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string, @scheme[start-pos] is a character position; when
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@scheme[input] is a byte string, then @scheme[start-pos] is a byte
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position; and when @scheme[input] is an input port, @scheme[start-pos]
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is the number of bytes to skip before starting to match. The
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@scheme[end-pos] argument can be @scheme[#f], which corresponds to the
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end of the string or the end-of-file in the stream; otherwise, it is a
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character or byte position, like @scheme[start-pos]. If @scheme[input]
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is an input port, and if the end-of-file is reached before
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@scheme[start-pos] bytes are skipped, then the match fails.
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In @scheme[pattern], a start-of-string @litchar{^} refers to the first
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position of @scheme[input] after @scheme[start-pos], and the
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end-of-input @litchar{$} refers to the @scheme[end-pos]th position or
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(in the case of an input port) the end of file, whichever comes first.
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If the match fails, @scheme[#f] is returned. If the match succeeds, a
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list containing strings or byte string, and possibly @scheme[#f], is
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returned. The list contains strings only if @scheme[input] is a string
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and @scheme[pattern] is not a byte regexp value. Otherwise, the list
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contains byte strings (substrings of the UTF-8 encoding of
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@scheme[input], if @scheme[input] is a string).
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The first [byte] string in a result list is the portion of
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@scheme[input] that matched @scheme[pattern]. If two portions of
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@scheme[input] can match @scheme[pattern], then the match that starts
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earliest is found.
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Additional [byte] strings are returned in the list if @scheme[pattern]
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contains parenthesized sub-expressions (but not when the open
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parenthesis is followed by @litchar{?:}). Matches for the
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sub-expressions are provided in the order of the opening parentheses
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in @scheme[pattern]. When sub-expressions occur in branches of an
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@litchar["|"] ``or'' pattern, in a @litchar{*} ``zero or more''
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pattern, or other places where the overall pattern can succeed without
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a match for the sub-expression, then a @scheme[#f] is returned for the
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sub-expression if it did not contribute to the final match. When a
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single sub-expression occurs within a @litchar{*} ``zero or more''
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pattern or other multiple-match positions, then the rightmost match
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associated with the sub-expression is returned in the list.
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If the optional @scheme[output-port] is provided as an output port,
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the part of @scheme[input] from its beginning (not @scheme[start-pos])
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that precedes the match is written to the port. All of @scheme[input]
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up to @scheme[end-pos] is written to the port if no match is
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found. This functionality is most useful when @scheme[input] is an
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input port.
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When matching an input port, a match failure reads up to
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@scheme[end-pos] bytes (or end-of-file), even if @scheme[pattern]
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begins with a start-of-string @litchar{^}; see also
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@scheme[regexp-try-match]. On success, all bytes up to and including
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the match are eventually read from the port, but matching proceeds by
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first peeking bytes from the port (using @scheme[peek-bytes-avail!]),
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and then (re-)reading matching bytes to discard them after the match
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result is determined. Non-matching bytes may be read and discarded
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before the match is determined. The matcher peeks in blocking mode
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only as far as necessary to determine a match, but it may peek extra
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bytes to fill an internal buffer if immediately available (i.e.,
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without blocking). Greedy repeat operators in @scheme[pattern], such
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as @litchar{*} or @litchar{+}, tend to force reading the entire
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content of the port (up to @scheme[end-pos]) to determine a match.
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If the input port is read simultaneously by another thread, or if the
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port is a custom port with inconsistent reading and peeking procedures
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(see @secref["customport"]), then the bytes that are peeked and
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used for matching may be different than the bytes read and discarded
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after the match completes; the matcher inspects only the peeked
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bytes. To avoid such interleaving, use @scheme[regexp-match-peek]
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(with a @scheme[progress-evt] argument) followed by
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@scheme[port-commit-peeked].
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@examples[
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(regexp-match #rx"x." "12x4x6")
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(regexp-match #rx"y." "12x4x6")
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(regexp-match #rx"x." "12x4x6" 3)
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(regexp-match #rx"x." "12x4x6" 3 4)
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(regexp-match #rx#"x." "12x4x6")
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(regexp-match #rx"x." "12x4x6" 0 #f (current-output-port))
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(regexp-match #rx"(-[0-9]*)+" "a-12--345b")
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]}
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@defproc[(regexp-match* [pattern (or/c string? bytes? regexp? byte-regexp?)]
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[input (or/c string? bytes? input-port?)]
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[start-pos nonnegative-exact-integer? 0]
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[end-pos (or/c nonnegative-exact-integer? false/c) #f])
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(listof (or/c string? bytes?))]{
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Like @scheme[regexp-match], but the result is a list of strings or
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byte strings corresponding to a sequence of matches of
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@scheme[pattern] in @scheme[input]. (Unlike @scheme[regexp-match],
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results for parenthesized sub-patterns in @scheme[pattern] are not
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returned.) If @scheme[pattern] matches a zero-length string or byte
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sequence along the way, the @exnraise[exn:fail].
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If @scheme[input] contains no matches (in the range @scheme[start-pos]
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to @scheme[end-pos]), @scheme[null] is returned. Otherwise, each item
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in the resulting list is a distinct substring or byte sequence from
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@scheme[input] that matches @scheme[pattern]. The @scheme[end-pos]
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argument can be @scheme[#f] to match to the end of @scheme[input]
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(which corresponds to an end-of-file if @scheme[input] is an input
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port).
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@examples[
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(regexp-match* #rx"x." "12x4x6")
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]}
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@defproc[(regexp-try-match
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[pattern (or/c string? bytes? regexp? byte-regexp?)]
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[input input-port?]
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[start-pos nonnegative-exact-integer? 0]
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[end-pos (or/c nonnegative-exact-integer? false/c) #f]
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[output-port (or/c output-port? false/c) #f])
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(or/c (listof (or/c (cons (or/c string? bytes?)
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(or/c string? bytes?))
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false/c))
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false/c)]{
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Like @scheme[regexp-match] on input ports, except that if the match
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fails, no characters are read and discarded from @scheme[in].
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This procedure is especially useful with a @scheme[pattern] that
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begins with a start-of-string @litchar{^} or with a non-@scheme[#f]
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@scheme[end-pos], since each limits the amount of peeking into the
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port. Otherwise, beware that a large portion of the stream may be
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peeked (and therefore pulled into memory) before the match succeeds or
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fails.}
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@defproc[(regexp-match-positions [pattern (or/c string? bytes? regexp? byte-regexp?)]
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[input (or/c string? bytes? input-port?)]
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[start-pos nonnegative-exact-integer? 0]
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[end-pos (or/c nonnegative-exact-integer? false/c) #f]
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[output-port (or/c output-port? false/c) #f])
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(or/c (listof (or/c (cons nonnegative-exact-integer?
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nonnegative-exact-integer?)
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false/c))
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false/c)]{
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Like @scheme[regexp-match], but returns a list of number pairs (and
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@scheme[#f]) instead of a list of strings. Each pair of numbers refers
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to a range of characters or bytes in @scheme[input]. If the result for
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the same arguments with @scheme[regexp-match] would be a list of byte
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strings, the resulting ranges correspond to byte ranges; in that case,
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if @scheme[input] is a character string, the byte ranges correspond to
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bytes in the UTF-8 encoding of the string.
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Range results are returned in a @scheme[substring]- and
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@scheme[subbytes]-compatible manner, independent of
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@scheme[start-pos]. In the case of an input port, the returned
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positions indicate the number of bytes that were read, including
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@scheme[start-pos], before the first matching byte.
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@examples[
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(regexp-match-positions #rx"x." "12x4x6")
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(regexp-match-positions #rx"x." "12x4x6" 3)
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(regexp-match-positions #rx"(-[0-9]*)+" "a-12--345b")
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]}
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@defproc[(regexp-match-positions* [pattern (or/c string? bytes? regexp? byte-regexp?)]
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[input (or/c string? bytes? input-port?)]
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[start-pos nonnegative-exact-integer? 0]
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[end-pos (or/c nonnegative-exact-integer? false/c) #f])
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(listof (cons nonnegative-exact-integer?
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nonnegative-exact-integer?))]{
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Like @scheme[regexp-match-positions], but returns multiple matches
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like @scheme[regexp-match*].
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@examples[
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(regexp-match-positions #rx"x." "12x4x6")
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]}
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@defproc[(regexp-match? [pattern (or/c string? bytes? regexp? byte-regexp?)]
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[input (or/c string? bytes? input-port?)]
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[start-pos nonnegative-exact-integer? 0]
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[end-pos (or/c nonnegative-exact-integer? false/c) #f]
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[output-port (or/c output-port? false/c) #f])
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boolean?]{
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Like @scheme[regexp-match], but returns merely @scheme[#t] when the
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match succeeds, @scheme[#f] otherwise.
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@examples[
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(regexp-match? #rx"x." "12x4x6")
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(regexp-match? #rx"y." "12x4x6")
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]}
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@defproc[(regexp-match-exact? [pattern (or/c string? bytes? regexp? byte-regexp?)]
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[input (or/c string? bytes? input-port?)])
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boolean?]{
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Like @scheme[regexp-match?], but @scheme[#t] is only returned when the
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entire content of @scheme[input] matches @scheme[pattern].
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@examples[
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(regexp-match-exact? #rx"x." "12x4x6")
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(regexp-match-exact? #rx"1.*x." "12x4x6")
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]}
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@defproc[(regexp-match-peek [pattern (or/c string? bytes? regexp? byte-regexp?)]
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[input input-port?]
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[start-pos nonnegative-exact-integer? 0]
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[end-pos (or/c nonnegative-exact-integer? false/c) #f]
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[progress (or/c evt false/c) #f])
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(or/c (listof (or/c (cons bytes? bytes?)
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false/c))
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false/c)]{
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Like @scheme[regexp-match] on input ports, but only peeks bytes from
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@scheme[input-port] instead of reading them. Furthermore, instead of
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an output port, the last optional argument is a progress event for
|
|
@scheme[input-port] (see @scheme[port-progress-evt]). If @scheme[progress]
|
|
becomes ready, then the match stops peeking from @scheme[input-port]
|
|
and returns @scheme[#f]. The @scheme[progress] argument can be
|
|
@scheme[#f], in which case the peek may continue with inconsistent
|
|
information if another process meanwhile reads from
|
|
@scheme[input-port].
|
|
|
|
@examples[
|
|
(define p (open-input-string "a abcd"))
|
|
(regexp-match-peek ".*bc" p)
|
|
(regexp-match-peek ".*bc" p 2)
|
|
(regexp-match ".*bc" p 2)
|
|
(peek-char p)
|
|
(regexp-match ".*bc" p)
|
|
(peek-char p)
|
|
]}
|
|
|
|
|
|
@defproc[(regexp-match-peek-positions [pattern (or/c string? bytes? regexp? byte-regexp?)]
|
|
[input input-port?]
|
|
[start-pos nonnegative-exact-integer? 0]
|
|
[end-pos (or/c nonnegative-exact-integer? false/c) #f]
|
|
[progress (or/c evt false/c) #f])
|
|
(or/c (listof (or/c (cons nonnegative-exact-integer?
|
|
nonnegative-exact-integer?)
|
|
false/c))
|
|
false/c)]{
|
|
|
|
Like @scheme[regexp-match-positions] on input ports, but only peeks
|
|
bytes from @scheme[input-port] instead of reading them, and with a
|
|
@scheme[progress] argument like @scheme[regexp-match-peek].}
|
|
|
|
|
|
@defproc[(regexp-match-peek-immediate [pattern (or/c string? bytes? regexp? byte-regexp?)]
|
|
[input input-port?]
|
|
[start-pos nonnegative-exact-integer? 0]
|
|
[end-pos (or/c nonnegative-exact-integer? false/c) #f]
|
|
[progress (or/c evt false/c) #f])
|
|
(or/c (listof (or/c (cons bytes? bytes?)
|
|
false/c))
|
|
false/c)]{
|
|
|
|
Like @scheme[regexp-match-peek], but it attempts to match only bytes
|
|
that are available from @scheme[input-port] without blocking. The
|
|
match fails if not-yet-available characters might be used to match
|
|
@scheme[pattern].}
|
|
|
|
|
|
@defproc[(regexp-match-peek-positions-immediate [pattern (or/c string? bytes? regexp? byte-regexp?)]
|
|
[input input-port?]
|
|
[start-pos nonnegative-exact-integer? 0]
|
|
[end-pos (or/c nonnegative-exact-integer? false/c) #f]
|
|
[progress (or/c evt false/c) #f])
|
|
(or/c (listof (or/c (cons nonnegative-exact-integer?
|
|
nonnegative-exact-integer?)
|
|
false/c))
|
|
false/c)]{
|
|
|
|
Like @scheme[regexp-match-peek-positions], but it attempts to match
|
|
only bytes that are available from @scheme[input-port] without
|
|
blocking. The match fails if not-yet-available characters might be
|
|
used to match @scheme[pattern].}
|
|
|
|
|
|
@defproc[(regexp-match-peek-positions* [pattern (or/c string? bytes? regexp? byte-regexp?)]
|
|
[input input-port?]
|
|
[start-pos nonnegative-exact-integer? 0]
|
|
[end-pos (or/c nonnegative-exact-integer? false/c) #f])
|
|
(listof (cons nonnegative-exact-integer?
|
|
nonnegative-exact-integer?))]{
|
|
|
|
Like @scheme[regexp-match-peek-positions], but returns multiple matches like
|
|
@scheme[regexp-match*].}
|
|
|
|
@;------------------------------------------------------------------------
|
|
@section{Regexp Splitting}
|
|
|
|
@defproc[(regexp-split [pattern (or/c string? bytes? regexp? byte-regexp?)]
|
|
[input (or/c string? bytes? input-port?)]
|
|
[start-pos nonnegative-exact-integer? 0]
|
|
[end-pos (or/c nonnegative-exact-integer? false/c) #f])
|
|
(listof (or/c string? bytes?))]{
|
|
|
|
The complement of @scheme[regexp-match*]: the result is a list of
|
|
strings (if @scheme[pattern] is a string or character regexp and
|
|
@scheme[input] is a string) or byte strings (otherwise) from in
|
|
@scheme[input] that are separated by matches to
|
|
@scheme[pattern]. Adjacent matches are separated with @scheme[""] or
|
|
@scheme[#""]. If @scheme[pattern] matches a zero-length string or byte
|
|
sequence along the way, the @exnraise[exn:fail].
|
|
|
|
If @scheme[input] contains no matches (in the range @scheme[start-pos]
|
|
to @scheme[end-pos]), the result is a list containing @scheme[input]'s
|
|
content (from @scheme[start-pos] to @scheme[end-pos]) as a single
|
|
element. If a match occurs at the beginning of @scheme[input] (at
|
|
@scheme[start-pos]), the resulting list will start with an empty
|
|
string or byte string, and if a match occurs at the end (at
|
|
@scheme[end-pos]), the list will end with an empty string or byte
|
|
string. The @scheme[end-pos] argument can be @scheme[#f], in which
|
|
case splitting goes to the end of @scheme[input] (which corresponds to
|
|
an end-of-file if @scheme[input] is an input port).
|
|
|
|
@examples[
|
|
(regexp-split #rx"x" "12x4x6")
|
|
(regexp-split #rx"." "12x4x6")
|
|
]}
|
|
|
|
@;------------------------------------------------------------------------
|
|
@section{Regexp Substitution}
|
|
|
|
@defproc[(regexp-replace [pattern (or/c string? bytes? regexp? byte-regexp?)]
|
|
[input (or/c string? bytes?)]
|
|
[insert (or/c string? bytes?
|
|
(string? . -> . string?)
|
|
(bytes? . -> . bytes?))])
|
|
(or/c string? bytes?)]{
|
|
|
|
Performs a match using @scheme[pattern] on @scheme[input], and then
|
|
returns a string or byte string in which the matching portion of
|
|
@scheme[input] is replaced with @scheme[insert]. If @scheme[pattern]
|
|
matches no part of @scheme[input], then @scheme[iput] is returned
|
|
unmodified.
|
|
|
|
If @scheme[pattern] is a string or character regexp and @scheme[input]
|
|
is a string, then @scheme[insert] must be a string or a procedure that
|
|
accept strings, and the result is a string. If @scheme[pattern] is a
|
|
byte string or byte regexp, or if @scheme[input] is a byte string,
|
|
then @scheme[insert] as a string is converted to a byte string,
|
|
@scheme[insert] as a procedure is called with a byte string, and the
|
|
result is a byte string.
|
|
|
|
If @scheme[insert] contains @litchar["&"], then @litchar["&"]
|
|
is replaced with the matching portion of @scheme[input] before it is
|
|
substituted into the match's place. If @scheme[insert] contains
|
|
@litchar["\\"]@nonterm{n} for some integer @nonterm{n}, then it is
|
|
replaced with the @nonterm{n}th matching sub-expression from
|
|
@scheme[input]. A @litchar{&} and @litchar["\\0"] are synonymous. If
|
|
the @nonterm{n}th sub-expression was not used in the match, or if
|
|
@nonterm{n} is greater than the number of sub-expressions in
|
|
@scheme[pattern], then @litchar["\\"]@nonterm{n} is replaced with the
|
|
empty string.
|
|
|
|
To substitute a literal @litchar{&} or @litchar["\\"], use
|
|
@litchar["\\&"] and @litchar["\\\\"], respectively, in
|
|
@scheme[insert]. A @litchar["\\$"] in @scheme[insert] is
|
|
equivalent to an empty sequence; this can be used to terminate a
|
|
number @nonterm{n} following @litchar["\\"]. If a @litchar["\\"] in
|
|
@scheme[insert] is followed by anything other than a digit,
|
|
@litchar{&}, @litchar["\\"], or @litchar{$}, then the @litchar["\\"]
|
|
by itself is treated as @litchar["\\0"].
|
|
|
|
Note that the @litchar["\\"] described in the previous paragraphs is a
|
|
character or byte of @scheme[input]. To write such an @scheme[input]
|
|
as a Scheme string literal, an escaping @litchar["\\"] is needed
|
|
before the @litchar["\\"]. For example, the Scheme constant
|
|
@scheme["\\1"] is @litchar["\\1"].
|
|
|
|
@examples[
|
|
(regexp-replace "mi" "mi casa" "su")
|
|
(regexp-replace "mi" "mi casa" string-upcase)
|
|
(regexp-replace "([Mm])i ([a-zA-Z]*)" "Mi Casa" "\\1y \\2")
|
|
(regexp-replace "([Mm])i ([a-zA-Z]*)" "mi cerveza Mi Mi Mi"
|
|
"\\1y \\2")
|
|
(regexp-replace #rx"x" "12x4x6" "\\\\")
|
|
(display (regexp-replace #rx"x" "12x4x6" "\\\\"))
|
|
]}
|
|
|
|
@defproc[(regexp-replace* [pattern (or/c string? bytes? regexp? byte-regexp?)]
|
|
[input (or/c string? bytes?)]
|
|
[insert (or/c string? bytes?
|
|
(string? . -> . string?)
|
|
(bytes? . -> . bytes?))])
|
|
(or/c string? bytes?)]{
|
|
|
|
Like @scheme[regexp-replace], except that every instance of
|
|
@scheme[pattern] in @scheme[input] is replaced with @scheme[insert],
|
|
instead of just the first match. Only non-overlapping instances of
|
|
@scheme[pattern] in @scheme[input] are replaced, so instances of
|
|
@scheme[pattern] within inserted strings are @italic{not} replaced
|
|
recursively. If, in the process of repeating matches, @scheme[pattern]
|
|
matches an empty string, the @exnraise[exn:fail].
|
|
|
|
@examples[
|
|
(regexp-replace* "([Mm])i ([a-zA-Z]*)" "mi cerveza Mi Mi Mi"
|
|
"\\1y \\2")
|
|
(regexp-replace* "([Mm])i ([a-zA-Z]*)" "mi cerveza Mi Mi Mi"
|
|
(lambda (all one two)
|
|
(string-append (string-downcase one) "y"
|
|
(string-upcase two))))
|
|
(display (regexp-replace* #rx"x" "12x4x6" "\\\\"))
|
|
]}
|
|
|
|
@defproc*[([(regexp-replace-quote [str string?]) string?]
|
|
[(regexp-replace-quote [bstr bytes?]) bytes?])]{
|
|
|
|
Produces a string suitable for use as the third argument to
|
|
@scheme[regexp-replace] to insert the literal sequence of characters
|
|
in @scheme[str] or bytes in @scheme[bstr] as a replacement.
|
|
Concretely, every @litchar["\\"] and @litchar{&} in @scheme[str] or
|
|
@scheme[bstr] is protected by a quoting @litchar["\\"].
|
|
|
|
@examples[
|
|
(regexp-replace "UT" "Go UT!" "A&M")
|
|
(regexp-replace "UT" "Go UT!" (regexp-replace-quote "A&M"))
|
|
]}
|
|
|