4.8 Regular Expressions (original) (raw)

4.8 Regular Expressions🔗ℹ

Regular Expressions in The Racket Guide introduces regular expressions.

Regular expressions are specified as strings or byte strings, using the same pattern language as either the Unix utilityegrep or Perl. A string-specified pattern produces a character regexp matcher, and a byte-string pattern produces a byte regexp matcher. If a character regexp is used with a byte string or input port, it matches UTF-8 encodings (see Encodings and Locales) of matching character streams; if a byte regexp is used with a character string, it matches bytes in the UTF-8 encoding of the string.

A regular expression that is represented as a string or byte string can be compiled to a regexp value, which can be used more efficiently by functions such as regexp-match compared to the string or byte string form. The regexp andbyte-regexp procedures convert a string or byte string (respectively) into a regexp value using a syntax of regular expressions that is most compatible to egrep. Thepregexp and byte-pregexp procedures produce a regexp value using a slightly different syntax of regular expressions that is more compatible with Perl.

Two regexp values are equal? if they have the same source, use the same pattern language, and are both character regexps or both byte regexps.

A literal or printed regexp value starts with #rx or#px. See Reading Regular Expressions for information on reading regular expressions and Printing Regular Expressions for information on printing regular expressions. Regexp values produced by the default reader are interned inread-syntax mode.

On the BC variant of Racket, the internal size of a regexp value is limited to 32 kilobytes; this limit roughly corresponds to a source string with 32,000 literal characters or 5,000 operators.

4.8.1 Regexp Syntax🔗ℹ

The following syntax specifications describe the content of a string that represents a regular expression. The syntax of the corresponding string may involve extra escape characters. For example, the regular expression (.*)\1 can be represented with the string"(.*)\\1" or the regexp constant #rx"(.*)\\1"; the\ in the regular expression must be escaped to include it in a string or regexp constant.

The regexp and pregexp syntaxes share a common core:

The following completes the grammar for regexp, which treats{ and } as literals, \ as a literal within ranges, and \ as a literal producer outside of ranges.

The following completes the grammar for pregexp, which uses{ and } bounded repetition and uses\ for meta-characters both inside and outside of ranges.

In case-insensitive mode, a backreference of the form\‹n› matches case-insensitively only with respect to ASCII characters.

The Unicode categories follow.

Examples:

> (regexp-match #rx"a|b" "cat") ; ex1
'("a")
> (regexp-match #rx"[at]" "cat") ; ex2
'("a")
> (regexp-match #rx"ca*[at]" "caaat") ; ex3
'("caaat")
> (regexp-match #rx"ca+[at]" "caaat") ; ex4
'("caaat")
> (regexp-match #rx"ca?t?" "ct") ; ex5
'("ct")
> (regexp-match #rx"ca*?[at]" "caaat") ; ex6
'("ca")
> (regexp-match #px"ca{2}" "caaat") ; ex7, uses #px
'("caa")
> (regexp-match #px"ca{2,}t" "catcaat") ; ex8, uses #px
'("caat")
> (regexp-match #px"ca{,2}t" "caaatcat") ; ex9, uses #px
'("cat")
> (regexp-match #px"ca{1,2}t" "caaatcat") ; ex10, uses #px
'("cat")
> (regexp-match #rx"(c<*)(a*)" "caat") ; ex11
'("caa" "c" "aa")
> (regexp-match #rx"[^ca]" "caat") ; ex12
'("t")
> (regexp-match #rx".(.)." "cat") ; ex13
'("cat" "a")
> (regexp-match #rx"^a|^c" "cat") ; ex14
'("c")
> (regexp-match #rx"a$|t$" "cat") ; ex15
'("t")
> (regexp-match #px"c(.)\\1t" "caat") ; ex16, uses #px
'("caat" "a")
> (regexp-match #px".\\b." "cat in hat") ; ex17, uses #px
'("t ")
> (regexp-match #px".\\B." "cat in hat") ; ex18, uses #px
'("ca")
> (regexp-match #px"\\p{Ll}" "Cat") ; ex19, uses #px
'("a")
> (regexp-match #px"\\P{Ll}" "cat!") ; ex20, uses #px
'("!")
> (regexp-match #rx"\\|" "c
'("|")
> (regexp-match #rx"[a-f]*" "cat") ; ex22
'("ca")
> (regexp-match #px"[a-f\\d]*" "1cat") ; ex23, uses #px
'("1ca")
> (regexp-match #px" [\\w]" "cat hat") ; ex24, uses #px
'(" h")
> (regexp-match #px"t[\\s]" "cat\nhat") ; ex25, uses #px
'("t\n")
> (regexp-match #px"[[:lower:]]+" "Cat") ; ex26, uses #px
'("at")
> (regexp-match #rx"[]]" "c]t") ; ex27
'("]")
> (regexp-match #rx"[-]" "c-t") ; ex28
'("-")
> (regexp-match #rx"[]a[]+" "c[a]t") ; ex29
'("[a]")
> (regexp-match #rx"[a^]+" "ca^t") ; ex30
'("a^")
> (regexp-match #rx".a(?=p)" "cat nap") ; ex31
'("na")
> (regexp-match #rx".a(?!t)" "cat nap") ; ex32
'("na")
> (regexp-match #rx"(?<=n)a." "cat nap") ; ex33
'("ap")
> (regexp-match #rx"(?<!c)a." "cat nap") ; ex34
'("ap")
> (regexp-match #rx"(?i:a)[tp]" "cAT nAp") ; ex35
'("Ap")
> (regexp-match #rx"(?(?<=c)a|b)+" "cabal") ; ex36
'("ab")
> (regexp-match #rx"[^^]+" "^cat^") ; ex37
'("cat")

4.8.2 Additional Syntactic Constraints🔗ℹ

In addition to matching a grammar, regular expressions must meet two syntactic restrictions:

• In a ‹repeat› other than ‹atom›?, the ‹atom› must not match an empty sequence.
• In a (?<=‹regexp›) or(?<!‹regexp›), the ‹regexp› must match a bounded sequence only.

These constraints are checked syntactically by the following type system. A type [n, m] corresponds to an expression that matches between n and m characters. In the rule for(‹Regexp›), N means the number such that the opening parenthesis is the Nth opening parenthesis for collecting match reports. Non-emptiness is inferred for a backreference pattern, \‹N›, so that a backreference can be used for repetition patterns; in the case of mutual dependencies among backreferences, the inference chooses the fixpoint that maximizes non-emptiness. Finiteness is not inferred for backreferences (i.e., a backreference is assumed to match an arbitrarily large sequence). No syntactic constraint prohibits a backreference within the group that it references, although such self references might create a pattern with no possible matches (as in the case of (.\1), although (^.|\1){2} matches an input that starts with the same two characters).

4.8.3 Regexp Constructors🔗ℹ

Returns #t if v is a regexp value created byregexp or pregexp, #f otherwise.

Returns #t if v is a regexp value created bypregexp (not regexp), #f otherwise.

Returns #t if v is a regexp value created bybyte-regexp or byte-pregexp, #f otherwise.

Returns #t if v is a regexp value created bybyte-pregexp (not byte-regexp), #fotherwise.

Takes a string representation of a regular expression (using the syntax in Regexp Syntax) and compiles it into a regexp value. Other regular expression procedures accept either a string or aregexp value as the matching pattern. If a regular expression string is used multiple times, it is faster to compile the string once to aregexp value and use it for repeated matches instead of using the string each time.

If handler is provided and not #f, it is called and its result is returned when str is not a valid representation of a regular expression; the argument to handler is a string that describes the problem with str. If handler is#f or not provided, then exn:fail:contract exception is raised.

The object-name procedure returns the source string for a regexp value.

Examples:

> (regexp "ap*le")
#rx"ap*le"
> (object-name #rx"ap*le")
"ap*le"
> (regexp "+" (λ (s) (list s)))
'("`+` follows nothing in pattern")

Changed in version 6.5.0.1 of package base: Added the handler argument.

Like regexp, except that it uses a slightly different syntax (see Regexp Syntax). The result can be used withregexp-match, etc., just like the result fromregexp.

Examples:

> (pregexp "ap*le")
#px"ap*le"
> (regexp? #px"ap*le")
#t
> (pregexp "+" (λ (s) (vector s)))
'#("`+` follows nothing in pattern")

Changed in version 6.5.0.1 of package base: Added the handler argument.

Takes a byte-string representation of a regular expression (using the syntax in Regexp Syntax) and compiles it into a byte-regexp value.

If handler is provided, it is called and its result is returned if bstr is not a valid representation of a regular expression.

The object-name procedure returns the source byte string for a regexp value.

Examples:

> (byte-regexp #"ap*le")
#rx#"ap*le"
> (object-name #rx#"ap*le")
#"ap*le"
> (byte-regexp "ap*le")
byte-regexp: contract violation
expected: bytes?
given: "ap*le"
> (byte-regexp #"+" (λ (s) (list s)))
'("`+` follows nothing in pattern")

Changed in version 6.5.0.1 of package base: Added the handler argument.

Like byte-regexp, except that it uses a slightly different syntax (see Regexp Syntax). The result can be used withregexp-match, etc., just like the result frombyte-regexp.

Examples:

> (byte-pregexp #"ap*le")
#px#"ap*le"
> (byte-pregexp #"+" (λ (s) (vector s)))
'#("`+` follows nothing in pattern")

Changed in version 6.5.0.1 of package base: Added the handler argument.

Produces a string or byte string suitable for use with regexpto match the literal sequence of characters in str or sequence of bytes in bstr. If case-sensitive? is true (the default), the resulting regexp matches letters instr or bstr case-sensitively, otherwise it matches case-insensitively.

Examples:

> (regexp-match "." "apple.scm")
'("a")
> (regexp-match (regexp-quote ".") "apple.scm")
'(".")

Like regexp-quote, but intended for use with pregexp. Escapes all non-alphanumeric, non-underscore characters in the input.

Added in version 8.11.1.9 of package base.

Returns the maximum number of bytes that pattern may consult before the starting position of a match to determine the match. For example, the pattern (?<=abc)d consults three bytes preceding a matching d, while e(?<=a..)d consults two bytes before a matching ed. A ^ pattern may consult a preceding byte to determine whether the current position is the start of the input or of a line.

Examples:

> (regexp-max-lookbehind #rx#"(?<=abc)d")
3
> (regexp-max-lookbehind #rx#"e(?<=a..)d")
2
> (regexp-max-lookbehind #rx"^")
1

4.8.4 Regexp Matching🔗ℹ

Attempts to match pattern (a string, byte string,regexp value, or byte-regexp value) once to a portion ofinput. The matcher finds a portion of input that matches and is closest to the start of the input (afterstart-pos).

If input is a path, it is converted to a byte string withpath->bytes if pattern is a byte string or a byte-based regexp. Otherwise, input is converted to a string with path->string.

The optional start-pos and end-pos arguments select a portion of input for matching; the default is the entire string or the stream up to an end-of-file. When input is a string, start-pos is a character position; wheninput is a byte string, then start-pos is a byte position; and when input is an input port, start-posis the number of bytes to skip before starting to match. Theend-pos argument can be #f, which corresponds to the end of the string or an end-of-file in the stream; otherwise, it is a character or byte position, like start-pos. If inputis an input port, and if an end-of-file is reached beforestart-pos bytes are skipped, then the match fails.

In pattern, a start-of-string ^ refers to the first position of input after start-pos, assuming thatinput-prefix is #"". The end-of-input $refers to the end-posth position or (in the case of an input port) an end-of-file, whichever comes first.

The input-prefix specifies bytes that effectively precedeinput for the purposes of ^ and other look-behind matching. For example, a #"" prefix means that ^matches at the beginning of the stream, while a #"\n" input-prefix means that a start-of-line ^ can match the beginning of the input, while a start-of-file ^ cannot.

If the match fails, #f is returned. If the match succeeds, a list containing strings or byte string, and possibly #f, is returned. The list contains strings only if input is a string and pattern is not a byte regexp. Otherwise, the list contains byte strings (substrings of the UTF-8 encoding ofinput, if input is a string).

The first [byte] string in a result list is the portion ofinput that matched pattern. If two portions ofinput can match pattern, then the match that starts earliest is found.

Additional [byte] strings are returned in the list if patterncontains parenthesized sub-expressions (but not when the opening parenthesis is followed by ?). Matches for the sub-expressions are provided in the order of the opening parentheses in pattern. When sub-expressions occur in branches of an| “or” pattern, in a * “zero or more” pattern, or other places where the overall pattern can succeed without a match for the sub-expression, then a #f is returned for the sub-expression if it did not contribute to the final match. When a single sub-expression occurs within a * “zero or more” pattern or other multiple-match positions, then the rightmost match associated with the sub-expression is returned in the list.

If the optional output-port is provided as an output port, the part of input from its beginning (not start-pos) that precedes the match is written to the port. All of inputup to end-pos is written to the port if no match is found. This functionality is most useful when input is an input port.

When matching an input port, a match failure reads up toend-pos bytes (or end-of-file), even if patternbegins with a start-of-string ^; see alsoregexp-try-match. On success, all bytes up to and including the match are eventually read from the port, but matching proceeds by first peeking bytes from the port (using peek-bytes-avail!), and then (re‑)reading matching bytes to discard them after the match result is determined. Non-matching bytes may be read and discarded before the match is determined. The matcher peeks in blocking mode only as far as necessary to determine a match, but it may peek extra bytes to fill an internal buffer if immediately available (i.e., without blocking). Greedy repeat operators in pattern, such as * or +, tend to force reading the entire content of the port (up to end-pos) to determine a match.

If the input port is read simultaneously by another thread, or if the port is a custom port with inconsistent reading and peeking procedures (see Custom Ports), then the bytes that are peeked and used for matching may be different than the bytes read and discarded after the match completes; the matcher inspects only the peeked bytes. To avoid such interleaving, use regexp-match-peek(with a progress-evt argument) followed byport-commit-peeked.

Examples:

> (regexp-match #rx"x." "12x4x6")
'("x4")
> (regexp-match #rx"y." "12x4x6")
#f
> (regexp-match #rx"x." "12x4x6" 3)
'("x6")
> (regexp-match #rx"x." "12x4x6" 3 4)
#f
> (regexp-match #rx#"x." "12x4x6")
'(#"x4")
> (regexp-match #rx"x." "12x4x6" 0 #f (current-output-port))
12
'("x4")
> (regexp-match #rx"(-[0-9]*)+" "a-12--345b")
'("-12--345" "-345")

Like regexp-match, but the result is a list of strings or byte strings corresponding to a sequence of matches ofpattern in input.

The pattern is used in order to find matches, where each match attempt starts at the end of the last match, and ^ is allowed to match the beginning of the input (if input-prefixis #"") only for the first match. Empty matches are handled like other matches, returning a zero-length string or byte sequence (they are more useful in making this a complement ofregexp-split), but pattern is restricted from matching an empty sequence immediately after an empty match.

If input contains no matches (in the range start-posto end-pos), null is returned. Otherwise, each item in the resulting list is a distinct substring or byte sequence frominput that matches pattern. The end-posargument can be #f to match to the end of input(which corresponds to an end-of-file if input is an input port).

Examples:

> (regexp-match* #rx"x." "12x4x6")
'("x4" "x6")
> (regexp-match* #rx"x*" "12x4x6")
'("" "" "x" "" "x" "" "")

match-select specifies the collected results. The default ofcar means that the result is the list of matches without returning parenthesized sub-patterns. It can be given as a ‘selector’ function which chooses an item from a list, or it can choose a list of items. For example, you can use cdr to get a list of lists of parenthesized sub-patterns matches, or values (as an identity function) to get the full matches as well. (Note that the selector must choose an element of its input list or a list of elements, but it must not inspect its input as they can be either a list of strings or a list of position pairs. Furthermore, the selector must be consistent in its choice(s).)

Examples:

> (regexp-match* #rx"x(.)" "12x4x6" #:match-select cadr)
'("4" "6")
> (regexp-match* #rx"x(.)" "12x4x6" #:match-select values)
'(("x4" "4") ("x6" "6"))

In addition, specifying gap-select as a non-#f value will make the result an interleaved list of the matches as well as the separators between them matches, starting and ending with a separator. In this case, match-select can be given as #f to return only the separators, making such uses equivalent toregexp-split.

Examples:

> (regexp-match* #rx"x(.)" "12x4x6" #:match-select cadr #:gap-select? #t)
'("12" "4" "" "6" "")
> (regexp-match* #rx"x(.)" "12x4x6" #:match-select #f #:gap-select? #t)
'("12" "" "")

Like regexp-match on input ports, except that if the match fails, no characters are read and discarded from in.

This procedure is especially useful with a pattern that begins with a start-of-string ^ or with a non-#f end-pos, since each limits the amount of peeking into the port. Otherwise, beware that a large portion of the stream may be peeked (and therefore pulled into memory) before the match succeeds or fails.

Like regexp-match, but returns a list of number pairs (and#f) instead of a list of strings. Each pair of numbers refers to a range of characters or bytes in input. If the result for the same arguments with regexp-match would be a list of byte strings, the resulting ranges correspond to byte ranges; in that case, if input is a character string, the byte ranges correspond to bytes in the UTF-8 encoding of the string.

Range results are returned in a substring- andsubbytes-compatible manner, independent ofstart-pos. In the case of an input port, the returned positions indicate the number of bytes that were read, includingstart-pos, before the first matching byte.

Examples:

> (regexp-match-positions #rx"x." "12x4x6")
'((2 . 4))
> (regexp-match-positions #rx"x." "12x4x6" 3)
'((4 . 6))
> (regexp-match-positions #rx"(-[0-9]*)+" "a-12--345b")
'((1 . 9) (5 . 9))

Range results after the first one can include negative numbers ifinput-prefix is non-empty and if pattern includes a lookbehind pattern. Such ranges start in the input-prefixinstead of input. More generally, when start-pos is positive, then range results that are less than start-posstart in input-prefix.

Examples:

> (regexp-match-positions #rx"(?<=(.))." "a" 0 #f #f #"x")
'((0 . 1) (-1 . 0))
> (regexp-match-positions #rx"(?<=(..))." "a" 0 #f #f #"x")
#f
> (regexp-match-positions #rx"(?<=(..))." "_a" 1 #f #f #"x")
#f

Although input-prefix is always a byte string, when the returned positions are string indices and they refer to a portion ofinput-prefix, then they correspond to a UTF-8 decoding of a tail of input-prefix.

Examples:

Like regexp-match-positions, but returns multiple matches like regexp-match*.

Examples:

> (regexp-match-positions* #rx"x." "12x4x6")
'((2 . 4) (4 . 6))
> (regexp-match-positions* #rx"x(.)" "12x4x6" #:match-select cadr)
'((3 . 4) (5 . 6))

Note that unlike regexp-match*, there is no#:gap-select? input keyword, as this information can be easily inferred from the resulting matches.

Like regexp-match, but returns merely #t when the match succeeds, #f otherwise.

Examples:

> (regexp-match? #rx"x." "12x4x6")
#t
> (regexp-match? #rx"y." "12x4x6")
#f

Like regexp-match?, but #t is only returned when the first found match is to the entire content of input.

Examples:

> (regexp-match-exact? #rx"x." "12x4x6")
#f
> (regexp-match-exact? #rx"1.*x." "12x4x6")
#t

Beware that regexp-match-exact? can return #f ifpattern generates a partial match for input first, even ifpattern could also generate a complete match. To check if there is any match of pattern that covers all of input, userexexp-match? with ^(?:pattern)$instead.

Examples:

> (regexp-match-exact? #rx"a|ab" "ab")
#f
> (regexp-match? #rx"^(?:a|ab)$" "ab")
#t

The (?:) grouping is necessary because concatenation has lower precedence than alternation; the regular expression without it,^a|ab$, matches any input that either starts witha or ends with ab.

Example:

> (regexp-match? #rx"^a|ab$" "123ab")
#t

Like regexp-match on input ports, but only peeks bytes frominput instead of reading them. Furthermore, instead of an output port, the last optional argument is a progress event forinput (see port-progress-evt). If progressbecomes ready, then the match stops peeking from inputand returns #f. The progress argument can be#f, in which case the peek may continue with inconsistent information if another process meanwhile reads frominput.

Examples:

Like regexp-match-positions on input ports, but only peeks bytes from input instead of reading them, and with aprogress argument like regexp-match-peek.

Like regexp-match-peek, but it attempts to match only bytes that are available from input without blocking. The match fails if not-yet-available characters might be used to matchpattern.

Like regexp-match-peek-positions, but it attempts to match only bytes that are available from input without blocking. The match fails if not-yet-available characters might be used to match pattern.

Like regexp-match-peek-positions, but returns multiple matches likeregexp-match-positions*.

Like regexp-match, but with a second result: a byte string of up to count bytes that correspond to the input (possibly including the input-prefix) leading to the end of the match; the second result is #f if no match is found.

The second result can be useful as an input-prefix for attempting a second match on input starting from the end of the first match. In that case, use regexp-max-lookbehindto determine an appropriate value for count.

Like regexp-match-positions, etc., but with a second result like regexp-match/end.

4.8.5 Regexp Splitting🔗ℹ

The complement of regexp-match*: the result is a list of strings (if pattern is a string or character regexp andinput is a string) or byte strings (otherwise) frominput that are separated by matches topattern. Adjacent matches are separated with "" or#"". Zero-length matches are treated the same as forregexp-match*.

If input contains no matches (in the range start-posto end-pos), the result is a list containing input’s content (from start-pos to end-pos) as a single element. If a match occurs at the beginning of input (atstart-pos), the resulting list will start with an empty string or byte string, and if a match occurs at the end (atend-pos), the list will end with an empty string or byte string. The end-pos argument can be #f, in which case splitting goes to the end of input (which corresponds to an end-of-file if input is an input port).

Examples:

> (regexp-split #rx" +" "12 34")
'("12" "34")
> (regexp-split #rx"." "12 34")
'("" "" "" "" "" "" "")
> (regexp-split #rx"" "12 34")
'("" "1" "2" " " " " "3" "4" "")
> (regexp-split #rx" *" "12 34")
'("" "1" "2" "" "3" "4" "")
> (regexp-split #px"\\b" "12, 13 and 14.")
'("" "12" ", " "13" " " "and" " " "14" ".")
> (regexp-split #rx" +" "")
'("")

4.8.6 Regexp Substitution🔗ℹ

Performs a match using pattern on input, and then returns a string or byte string in which the matching portion ofinput is replaced with insert. If patternmatches no part of input, then input is returned unmodified.

The insert argument can be either a (byte) string, or a function that returns a (byte) string. In the latter case, the function is applied on the list of values that regexp-matchwould return (i.e., the first argument is the complete match, and then one argument for each parenthesized sub-expression) to obtain a replacement (byte) string.

If pattern is a string or character regexp and inputis a string, then insert must be a string or a procedure that accept strings, and the result is a string. If pattern is a byte string or byte regexp, or if input is a byte string, then insert as a string is converted to a byte string,insert as a procedure is called with a byte string, and the result is a byte string.

If insert contains &, then &is replaced with the matching portion of input before it is substituted into the match’s place. If insert contains\‹n› for some integer ‹n›, then it is replaced with the ‹n›th matching sub-expression frominput. A & and \0 are aliases. If the ‹n›th sub-expression was not used in the match, or if‹n› is greater than the number of sub-expressions inpattern, then \‹n› is replaced with the empty string.

To substitute a literal & or \, use\& and \\, respectively, ininsert. A \$ in insert is equivalent to an empty sequence; this can be used to terminate a number ‹n› following \. If a \ ininsert is followed by anything other than a digit,&, \, or $, then the \by itself is treated as \0.

Note that the \ described in the previous paragraphs is a character or byte of insert. To write such an insertas a Racket string literal, an escaping \ is needed before the \. For example, the Racket constant"\\1" is \1.

Examples:

> (regexp-replace #rx"mi" "mi casa" "su")
"su casa"
> (regexp-replace #rx"mi" "mi casa" string-upcase)
"MI casa"
> (regexp-replace #rx"([Mm])i ([a-zA-Z]*)" "Mi Casa" "\\1y \\2")
"My Casa"
> (regexp-replace #rx"([Mm])i ([a-zA-Z]*)" "mi cerveza Mi Mi Mi" "\\1y \\2")
"my cerveza Mi Mi Mi"
> (regexp-replace #rx"x" "12x4x6" "\\\\")
"12\\4x6"
> (display (regexp-replace #rx"x" "12x4x6" "\\\\"))
12\4x6

Like regexp-replace, except that every instance ofpattern in input is replaced with insert, instead of just the first match. The result is input only if there are no matches, start-pos is 0, andend-pos is #f or the length of input. Only non-overlapping instances ofpattern in input are replaced, so instances ofpattern within inserted strings are not replaced recursively. Zero-length matches are treated the same as inregexp-match*.

The optional start-pos and end-pos arguments select a portion of input for matching; the default is the entire string or the stream up to an end-of-file.

Examples:

> (regexp-replace* #rx"([Mm])i ([a-zA-Z]*)" "mi cerveza Mi Mi Mi" "\\1y \\2")
"my cerveza My Mi Mi"
"myCERVEZA myMI Mi"
> (regexp-replace* #px"\\w" "hello world" string-upcase 0 5)
"HELLO world"
> (display (regexp-replace* #rx"x" "12x4x6" "\\\\"))
12\4\6

Changed in version 8.1.0.7 of package base: Changed to return input when no replacements are performed.

Performs a chain of regexp-replace* operations, where each element in replacements specifies a replacement as a(list pattern replacement). The replacements are done in order, so later replacements can apply to previous insertions.

Examples:

> (regexp-replaces "zero-or-more?" '([#rx"-" "_"] [#rx"(.*)\\?$" "is_\\1"]))
"is_zero_or_more"
> (regexp-replaces "zero-or-more?" '([#rx"e" "o"] [#rx"o" "oo"]))
"zooroo-oor-mooroo?"

Produces a string suitable for use as the third argument toregexp-replace to insert the literal sequence of characters in str or bytes in bstr as a replacement. Concretely, every \ and & in str orbstr is protected by a quoting \.

Examples:

> (regexp-replace #rx"UT" "Go UT!" "A&M")
"Go AUTM!"
> (regexp-replace #rx"UT" "Go UT!" (regexp-replace-quote "A&M"))
"Go A&M!"