Abstract
CL-PPCRE is a portable regular expression library for Common Lisp which has the following features:CL-PPCRE has been used successfully in various applications like BioBike, clutu, LoGS, CafeSpot, Eboy, or The Regex Coach.
- It is compatible with Perl.
- It is pretty fast.
- It is portable between ANSI-compliant Common Lisp implementations.
- It is thread-safe.
- In addition to specifying regular expressions as strings like in Perl you can also use S-expressions.
- It comes with a BSD-style license so you can basically do with it whatever you want.
Download shortcut: http://weitz.de/files/cl-ppcre.tar.gz.
undef
in $1
, $2
, etc.
$1
, $2
, etc.
"\r"
doesn't work with MCL
"\w"
?
CL-PPCRE comes with a system definition for ASDF and you compile and load it in the usual way. There are no dependencies (except that the test suite which is not needed for normal operation depends on FLEXI-STREAMS).
CL-PPCRE is integrated into the package/port systems of Debian, Gentoo, and FreeBSD, but before you install it from there, you should check if they actually offer the latest release. Installation via ASDF-Install should as well be possible.
You can run a test suite which tests most aspects of the library with
(asdf:oos 'asdf:test-op :cl-ppcre)
Luís Oliveira maintains a darcs
repository of CL-PPCRE
at http://common-lisp.net/~loliveira/ediware/.
If you want to send patches, please read this first.
Accepts a string which is a regular expression in Perl syntax and returns a closure which will scan strings for this regular expression. The second value is only returned if*ALLOW-NAMED-REGISTERS*
is true. It represents a list of strings mapping registers to their respective names - the first element stands for first register, the second element for second register, etc. You have to store this value if you want to map a register number to its name later as scanner doesn't capture any information about register names. If a register isn't named, it has NIL as its name.The mode keyword arguments are equivalent to the
"imsx"
modifiers in Perl. Thedestructive
keyword will be ignored.The function accepts most of the regex syntax of Perl 5.8 as described in
man perlre
including extended features like non-greedy repetitions, positive and negative look-ahead and look-behind assertions, "standalone" subexpressions, and conditional subpatterns. The following Perl features are (currently) not supported:Note, however, that
(?{ code })
and(??{ code })
because they obviously don't make sense in Lisp.\N{name}
(named characters),\x{263a}
(wide hex characters),\l
,\u
,\L
, and\U
because they're actually not part of Perl's regex syntax - but see CL-INTERPOL.\X
(extended Unicode), and\C
(single character). But you can of course use all characters supported by your CL implementation.- Posix character classes like
[[:alpha]]
. Use Unicode properties instead.\G
for Perl'spos()
because we don't have it.\t
,\n
,\r
,\f
,\a
,\e
,\033
(octal character codes),\x1B
(hexadecimal character codes),\c[
(control characters),\w
,\W
,\s
,\S
,\d
,\D
,\b
,\B
,\A
,\Z
, and\z
are supported.Since version 0.6.0, CL-PPCRE also supports Perl's
\Q
and\E
- see*ALLOW-QUOTING*
below. Make sure you also read the relevant section in "Bugs and problems."Since version 1.3.0, CL-PPCRE offers support for AllegroCL's
(?<name>"<regex>")
named registers and\k<name>
back-references syntax, have a look at*ALLOW-NAMED-REGISTERS*
for details.Since version 2.0.0, CL-PPCRE supports named properties (
\p
and\P
), but only the long form with braces is supported, i.e.\p{Letter}
and\p{L}
will work while\pL
won't.The keyword arguments are just for your convenience. You can always use embedded modifiers like
"(?i-s)"
instead.
In this casefunction
should be a scanner returned by another invocation ofCREATE-SCANNER
. It will be returned as is. You can't use any of the keyword arguments because the scanner has already been created and is immutable.
This is similar toCREATE-SCANNER
for regex strings above but accepts a parse tree as its first argument. A parse tree is an S-expression conforming to the following syntax:Because
- Every string and character is a parse tree and is treated literally as a part of the regular expression, i.e. parentheses, brackets, asterisks and such aren't special.
- The symbol
:VOID
is equivalent to the empty string.- The symbol
:EVERYTHING
is equivalent to Perl's dot, i.e it matches everything (except maybe a newline character depending on the mode).- The symbols
:WORD-BOUNDARY
and:NON-WORD-BOUNDARY
are equivalent to Perl's"\b"
and"\B"
.- The symbols
:DIGIT-CLASS
,:NON-DIGIT-CLASS
,:WORD-CHAR-CLASS
,:NON-WORD-CHAR-CLASS
,:WHITESPACE-CHAR-CLASS
, and:NON-WHITESPACE-CHAR-CLASS
are equivalent to Perl's special character classes"\d"
,"\D"
,"\w"
,"\W"
,"\s"
, and"\S"
respectively.- The symbols
:START-ANCHOR
,:END-ANCHOR
,:MODELESS-START-ANCHOR
,:MODELESS-END-ANCHOR
, and:MODELESS-END-ANCHOR-NO-NEWLINE
are equivalent to Perl's"^"
,"$"
,"\A"
,"\Z"
, and"\z"
respectively.- The symbols
:CASE-INSENSITIVE-P
,:CASE-SENSITIVE-P
,:MULTI-LINE-MODE-P
,:NOT-MULTI-LINE-MODE-P
,:SINGLE-LINE-MODE-P
, and:NOT-SINGLE-LINE-MODE-P
are equivalent to Perl's embedded modifiers"(?i)"
,"(?-i)"
,"(?m)"
,"(?-m)"
,"(?s)"
, and"(?-s)"
. As usual, changes applied to modes are kept local to the innermost enclosing grouping or clustering construct.- All other symbols will signal an error of type
PPCRE-SYNTAX-ERROR
unless they are defined to be parse tree synonyms.(:FLAGS {<modifier>}*)
where<modifier>
is one of the modifier symbols from above is used to group modifier symbols. The modifiers are applied from left to right. (This construct is obviously redundant. It is only there because it's used by the parser.)(:SEQUENCE {<parse-tree>}*)
means a sequence of parse trees, i.e. the parse trees must match one after another. Example:(:SEQUENCE #\f #\o #\o)
is equivalent to the parse tree"foo"
.(:GROUP {<parse-tree>}*)
is like:SEQUENCE
but changes applied to modifier flags (see above) are kept local to the parse trees enclosed by this construct. Think of it as the S-expression variant of Perl's"(?:<pattern>)"
construct.(:ALTERNATION {<parse-tree>}*)
means an alternation of parse trees, i.e. one of the parse trees must match. Example:(:ALTERNATION #\b #\a #\z)
is equivalent to the Perl regex string"b|a|z"
.(:BRANCH <test> <parse-tree>)
is for conditional regular expressions.<test>
is either a number which stands for a register or a parse tree which is a look-ahead or look-behind assertion. See the entry for(?(<condition>)<yes-pattern>|<no-pattern>)
inman perlre
for the semantics of this construct. If<parse-tree>
is an alternation is must enclose exactly one or two parse trees where the second one (if present) will be treated as the "no-pattern" - in all other cases<parse-tree>
will be treated as the "yes-pattern".(:POSITIVE-LOOKAHEAD|:NEGATIVE-LOOKAHEAD|:POSITIVE-LOOKBEHIND|:NEGATIVE-LOOKBEHIND <parse-tree>)
should be pretty obvious...(:GREEDY-REPETITION|:NON-GREEDY-REPETITION <min> <max> <parse-tree>)
where<min>
is a non-negative integer and<max>
is either a non-negative integer not smaller than<min>
orNIL
will result in a regular expression which tries to match<parse-tree>
at least<min>
times and at most<max>
times (or as often as possible if<max>
isNIL
). So, e.g.,(:NON-GREEDY-REPETITION 0 1 "ab")
is equivalent to the Perl regex string"(?:ab)??"
.(:STANDALONE <parse-tree>)
is an "independent" subexpression, i.e.(:STANDALONE "bar")
is equivalent to the Perl regex string"(?>bar)"
.(:REGISTER <parse-tree>)
is a capturing register group. As usual, registers are counted from left to right beginning with 1.(:NAMED-REGISTER <name> <parse-tree>)
is a named capturing register group. Acts as:REGISTER
, but assigns<name>
to a register too. This<name>
can be later referred to via:BACK-REFERENCE
. Names are case-sensitive and don't need to be unique. See*ALLOW-NAMED-REGISTERS*
for details.(:BACK-REFERENCE <ref>)
is a back-reference to a register group.<ref>
is a positive integer or a string denoting a register name. If there are several registers with the same name, the regex engine tries to successfully match at least of them, starting with the most recently seen register continuing to the least recently seen one, until a match is found. See*ALLOW-NAMED-REGISTERS*
for more information.(:PROPERTY|:INVERTED-PROPERTY <property>)
is a named property (or its inverse) with<property>
being a function designator or a string which must be resolved by*PROPERTY-RESOLVER*
.(:FILTER <function> &optional <length>)
where<function>
is a function designator and<length>
is a non-negative integer orNIL
is a user-defined filter.(:REGEX <string>)
where<string>
is an embedded regular expression in Perl syntax.(:CHAR-CLASS|:INVERTED-CHAR-CLASS {<item>}*)
where<item>
is either a character, a character range, a named property (see above), or a symbol for a special character class (see above) will be translated into a (one character wide) character class. A character range looks like(:RANGE <char1> <char2>)
where<char1>
and<char2>
are characters such that(CHAR<= <char1> <char2>)
is true. Example:(:INVERTED-CHAR-CLASS #\a (:RANGE #\D #\G) :DIGIT-CLASS)
is equivalent to the Perl regex string"[^aD-G\d]"
.CREATE-SCANNER
is defined as a generic function which dispatches on its first argument there's a certain ambiguity: Although strings are valid parse trees they will be interpreted as Perl regex strings when given toCREATE-SCANNER
. To circumvent this you can always use the equivalent parse tree(:GROUP <string>)
instead.Note that
CREATE-SCANNER
doesn't always check for the well-formedness of its first argument, i.e. you are expected to provide correct parse trees.The usage of the keyword argument
extended-mode
obviously doesn't make sense ifCREATE-SCANNER
is applied to parse trees and will signal an error.If
destructive
is notNIL
(the default isNIL
), the function is allowed to destructively modifyparse-tree
while creating the scanner.If you want to find out how parse trees are related to Perl regex strings, you should play around with
PARSE-STRING
:* (parse-string "(ab)*") (:GREEDY-REPETITION 0 NIL (:REGISTER "ab")) * (parse-string "(a(b))") (:REGISTER (:SEQUENCE #\a (:REGISTER #\b))) * (parse-string "(?:abc){3,5}") (:GREEDY-REPETITION 3 5 (:GROUP "abc")) ;; (:GREEDY-REPETITION 3 5 "abc") would also be OK * (parse-string "a(?i)b(?-i)c") (:SEQUENCE #\a (:SEQUENCE (:FLAGS :CASE-INSENSITIVE-P) (:SEQUENCE #\b (:SEQUENCE (:FLAGS :CASE-SENSITIVE-P) #\c)))) ;; same as (:SEQUENCE #\a :CASE-INSENSITIVE-P #\b :CASE-SENSITIVE-P #\c) * (parse-string "(?=a)b") (:SEQUENCE (:POSITIVE-LOOKAHEAD #\a) #\b)
For the rest of the dictionary, regex
can
always be a string (which is interpreted as a Perl regular
expression), a parse tree, or a scanner created by
CREATE-SCANNER
. The
start
and end
keyword parameters are always used as in SCAN
.
[Generic Function]
scan regex target-string &key start end => match-start, match-end, reg-starts, reg-ends
Searches the stringtarget-string
fromstart
(which defaults to 0) toend
(which default to the length oftarget-string
) and tries to matchregex
. On success returns four values - the start of the match, the end of the match, and two arrays denoting the beginnings and ends of register matches. On failure returnsNIL
.target-string
will be coerced to a simple string if it isn't one already. (There's another keyword parameterreal-start-pos
. This one should never be set from user code - it is only used internally.)
SCAN
acts as if the part oftarget-string
betweenstart
andend
were a standalone string, i.e. look-aheads and look-behinds can't look beyond these boundaries.* (scan "(a)*b" "xaaabd") 1 5 #(3) #(4) * (scan "(a)*b" "xaaabd" :start 1) 1 5 #(3) #(4) * (scan "(a)*b" "xaaabd" :start 2) 2 5 #(3) #(4) * (scan "(a)*b" "xaaabd" :end 4) NIL * (scan '(:greedy-repetition 0 nil #\b) "bbbc") 0 3 #() #() * (scan '(:greedy-repetition 4 6 #\b) "bbbc") NIL * (let ((s (create-scanner "(([a-c])+)x"))) (scan s "abcxy")) 0 4 #(0 2) #(3 3)
[Function]
scan-to-strings regex target-string &key start end sharedp => match, regs
LikeSCAN
but returns substrings oftarget-string
instead of positions, i.e. this function returns two values on success: the whole match as a string plus an array of substrings (orNIL
s) corresponding to the matched registers. Ifsharedp
is true, the substrings may share structure withtarget-string
.* (scan-to-strings "[^b]*b" "aaabd") "aaab" #() * (scan-to-strings "([^b])*b" "aaabd") "aaab" #("a") * (scan-to-strings "(([^b])*)b" "aaabd") "aaab" #("aaa" "a")
Evaluatesstatement*
with the variables invar-list
bound to the corresponding register groups aftertarget-string
has been matched againstregex
, i.e. each variable is either bound to a string or toNIL
. As a shortcut, the elements ofvar-list
can also be lists of the form(FN VAR)
whereVAR
is the variable symbol andFN
is a function designator (which is evaluated) denoting a function which is to be applied to the string before the result is bound toVAR
. To make this even more convenient the form(FN VAR1 ...VARn)
can be used as an abbreviation for(FN VAR1) ... (FN VARn)
.If there is no match, the
statement*
forms are not executed. For each element ofvar-list
which isNIL
there's no binding to the corresponding register group. The number of variables invar-list
must not be greater than the number of register groups. Ifsharedp
is true, the substrings may share structure withtarget-string
.* (register-groups-bind (first second third fourth) ("((a)|(b)|(c))+" "abababc" :sharedp t) (list first second third fourth)) ("c" "a" "b" "c") * (register-groups-bind (nil second third fourth) ;; note that we don't bind the first and fifth register group ("((a)|(b)|(c))()+" "abababc" :start 6) (list second third fourth)) (NIL NIL "c") * (register-groups-bind (first) ("(a|b)+" "accc" :start 1) (format t "This will not be printed: ~A" first)) NIL * (register-groups-bind (fname lname (#'parse-integer date month year)) ("(\\w+)\\s+(\\w+)\\s+(\\d{1,2})\\.(\\d{1,2})\\.(\\d{4})" "Frank Zappa 21.12.1940") (list fname lname (encode-universal-time 0 0 0 date month year 0))) ("Frank" "Zappa" 1292889600)
A macro which iterates overtarget-string
and tries to matchregex
as often as possible evaluatingstatement*
withmatch-start
,match-end
,reg-starts
, andreg-ends
bound to the four return values of each match (seeSCAN
) in turn. After the last match, returnsresult-form
if provided orNIL
otherwise. An implicit block namedNIL
surroundsDO-SCANS
;RETURN
may be used to terminate the loop immediately. Ifregex
matches an empty string, the scan is continued one position behind this match.This is the most general macro to iterate over all matches in a target string. See the source code of
DO-MATCHES
,ALL-MATCHES
,SPLIT
, orREGEX-REPLACE-ALL
for examples of its usage.
LikeDO-SCANS
but doesn't bind variables to the register arrays.* (defun foo (regex target-string &key (start 0) (end (length target-string))) (let ((sum 0)) (do-matches (s e regex target-string nil :start start :end end) (incf sum (- e s))) (format t "~,2F% of the string was inside of a match~%" ;; note: doesn't check for division by zero (float (* 100 (/ sum (- end start))))))) FOO * (foo "a" "abcabcabc") 33.33% of the string was inside of a match NIL * (foo "aa|b" "aacabcbbc") 55.56% of the string was inside of a match NIL
LikeDO-MATCHES
but bindsmatch-var
to the substring oftarget-string
corresponding to each match in turn. Ifsharedp
is true, the substrings may share structure withtarget-string
.* (defun crossfoot (target-string &key (start 0) (end (length target-string))) (let ((sum 0)) (do-matches-as-strings (m :digit-class target-string nil :start start :end end) (incf sum (parse-integer m))) (if (< sum 10) sum (crossfoot (format nil "~A" sum))))) CROSSFOOT * (crossfoot "bar") 0 * (crossfoot "a3x") 3 * (crossfoot "12345") 6Of course, in real life you would do this withDO-MATCHES
and use thestart
andend
keyword parameters ofPARSE-INTEGER
.
Iterates overtarget-string
and tries to matchregex
as often as possible evaluatingstatement*
with the variables invar-list
bound to the corresponding register groups for each match in turn, i.e. each variable is either bound to a string or toNIL
. You can use the same shortcuts and abbreviations as inREGISTER-GROUPS-BIND
. The number of variables invar-list
must not be greater than the number of register groups. For each element ofvar-list
which isNIL
there's no binding to the corresponding register group. After the last match, returnsresult-form
if provided orNIL
otherwise. An implicit block namedNIL
surroundsDO-REGISTER-GROUPS
;RETURN
may be used to terminate the loop immediately. Ifregex
matches an empty string, the scan is continued one position behind this match. Ifsharedp
is true, the substrings may share structure withtarget-string
.* (do-register-groups (first second third fourth) ("((a)|(b)|(c))" "abababc" nil :start 2 :sharedp t) (print (list first second third fourth))) ("a" "a" NIL NIL) ("b" NIL "b" NIL) ("a" "a" NIL NIL) ("b" NIL "b" NIL) ("c" NIL NIL "c") NIL * (let (result) (do-register-groups ((#'parse-integer n) (#'intern sign) whitespace) ("(\\d+)|(\\+|-|\\*|/)|(\\s+)" "12*15 - 42/3") (unless whitespace (push (or n sign) result))) (nreverse result)) (12 * 15 - 42 / 3)
[Function]
all-matches regex target-string &key start end => list
Returns a list containing the start and end positions of all matches ofregex
againsttarget-string
, i.e. if there areN
matches the list contains(* 2 N)
elements. Ifregex
matches an empty string the scan is continued one position behind this match.* (all-matches "a" "foo bar baz") (5 6 9 10) * (all-matches "\\w*" "foo bar baz") (0 3 3 3 4 7 7 7 8 11 11 11)
[Function]
all-matches-as-strings regex target-string &key start end sharedp => list
LikeALL-MATCHES
but returns a list of substrings instead. Ifsharedp
is true, the substrings may share structure withtarget-string
.* (all-matches-as-strings "a" "foo bar baz") ("a" "a") * (all-matches-as-strings "\\w*" "foo bar baz") ("foo" "" "bar" "" "baz" "")
[Function]
split regex target-string &key start end limit with-registers-p omit-unmatched-p sharedp => list
Matchesregex
againsttarget-string
as often as possible and returns a list of the substrings between the matches. Ifwith-registers-p
is true, substrings corresponding to matched registers are inserted into the list as well. Ifomit-unmatched-p
is true, unmatched registers will simply be left out, otherwise they will show up asNIL
.limit
limits the number of elements returned - registers aren't counted. Iflimit
isNIL
(or 0 which is equivalent), trailing empty strings are removed from the result list. Ifregex
matches an empty string, the scan is continued one position behind this match. Ifsharedp
is true, the substrings may share structure withtarget-string
.This function also tries hard to be Perl-compatible - thus the somewhat peculiar behaviour.
* (split "\\s+" "foo bar baz frob") ("foo" "bar" "baz" "frob") * (split "\\s*" "foo bar baz") ("f" "o" "o" "b" "a" "r" "b" "a" "z") * (split "(\\s+)" "foo bar baz") ("foo" "bar" "baz") * (split "(\\s+)" "foo bar baz" :with-registers-p t) ("foo" " " "bar" " " "baz") * (split "(\\s)(\\s*)" "foo bar baz" :with-registers-p t) ("foo" " " "" "bar" " " " " "baz") * (split "(,)|(;)" "foo,bar;baz" :with-registers-p t) ("foo" "," NIL "bar" NIL ";" "baz") * (split "(,)|(;)" "foo,bar;baz" :with-registers-p t :omit-unmatched-p t) ("foo" "," "bar" ";" "baz") * (split ":" "a:b:c:d:e:f:g::") ("a" "b" "c" "d" "e" "f" "g") * (split ":" "a:b:c:d:e:f:g::" :limit 1) ("a:b:c:d:e:f:g::") * (split ":" "a:b:c:d:e:f:g::" :limit 2) ("a" "b:c:d:e:f:g::") * (split ":" "a:b:c:d:e:f:g::" :limit 3) ("a" "b" "c:d:e:f:g::") * (split ":" "a:b:c:d:e:f:g::" :limit 1000) ("a" "b" "c" "d" "e" "f" "g" "" "")
Try to matchtarget-string
betweenstart
andend
againstregex
and replace the first match withreplacement
. Two values are returned; the modified string, andT
ifregex
matched orNIL
otherwise.
replacement
can be a string which may contain the special substrings"\&"
for the whole match,"\`"
for the part oftarget-string
before the match,"\'"
for the part oftarget-string
after the match,"\N"
or"\{N}"
for theN
th register whereN
is a positive integer.
replacement
can also be a function designator in which case the match will be replaced with the result of calling the function designated byreplacement
with the argumentstarget-string
,start
,end
,match-start
,match-end
,reg-starts
, andreg-ends
. (reg-starts
andreg-ends
are arrays holding the start and end positions of matched registers (orNIL
) - the meaning of the other arguments should be obvious.)If
simple-calls
is true, a function designated byreplacement
will instead be called with the argumentsmatch
,register-1
, ...,register-n
wherematch
is the whole match as a string andregister-1
toregister-n
are the matched registers, also as strings (orNIL
). Note that these strings share structure withtarget-string
so you must not modify them.Finally,
replacement
can be a list where each element is a string (which will be inserted verbatim), one of the symbols:match
,:before-match
, or:after-match
(corresponding to"\&"
,"\`"
, and"\'"
above), an integerN
(representing register(1+ N)
), or a function designator.If
preserve-case
is true (default isNIL
), the replacement will try to preserve the case (all upper case, all lower case, or capitalized) of the match. The result will always be a fresh string, even ifregex
doesn't match.
element-type
specifies the array element type of the string which is returned, the default isLW:SIMPLE-CHAR
for LispWorks andCHARACTER
for other Lisps.* (regex-replace "fo+" "foo bar" "frob") "frob bar" T * (regex-replace "fo+" "FOO bar" "frob") "FOO bar" NIL * (regex-replace "(?i)fo+" "FOO bar" "frob") "frob bar" T * (regex-replace "(?i)fo+" "FOO bar" "frob" :preserve-case t) "FROB bar" T * (regex-replace "(?i)fo+" "Foo bar" "frob" :preserve-case t) "Frob bar" T * (regex-replace "bar" "foo bar baz" "[frob (was '\\&' between '\\`' and '\\'')]") "foo [frob (was 'bar' between 'foo ' and ' baz')] baz" T * (regex-replace "bar" "foo bar baz" '("[frob (was '" :match "' between '" :before-match "' and '" :after-match "')]")) "foo [frob (was 'bar' between 'foo ' and ' baz')] baz" T * (regex-replace "(be)(nev)(o)(lent)" "benevolent: adj. generous, kind" #'(lambda (match &rest registers) (format nil "~A [~{~A~^.~}]" match registers)) :simple-calls t) "benevolent [be.nev.o.lent]: adj. generous, kind" T
LikeREGEX-REPLACE
but replaces all matches.* (regex-replace-all "(?i)fo+" "foo Fooo FOOOO bar" "frob" :preserve-case t) "frob Frob FROB bar" T * (regex-replace-all "(?i)f(o+)" "foo Fooo FOOOO bar" "fr\\1b" :preserve-case t) "froob Frooob FROOOOB bar" T * (let ((qp-regex (create-scanner "[\\x80-\\xff]"))) (defun encode-quoted-printable (string) "Converts 8-bit string to quoted-printable representation." ;; won't work for Corman Lisp because non-ASCII characters aren't 8-bit there (flet ((convert (target-string start end match-start match-end reg-starts reg-ends) (declare (ignore start end match-end reg-starts reg-ends)) (format nil "=~2,'0x" (char-code (char target-string match-start))))) (regex-replace-all qp-regex string #'convert)))) Converted ENCODE-QUOTED-PRINTABLE. ENCODE-QUOTED-PRINTABLE * (encode-quoted-printable "Fête Sørensen naïve Hühner Straße") "F=EAte S=F8rensen na=EFve H=FChner Stra=DFe" T * (let ((url-regex (create-scanner "[^a-zA-Z0-9_\\-.]"))) (defun url-encode (string) "URL-encodes a string." ;; won't work for Corman Lisp because non-ASCII characters aren't 8-bit there (flet ((convert (target-string start end match-start match-end reg-starts reg-ends) (declare (ignore start end match-end reg-starts reg-ends)) (format nil "%~2,'0x" (char-code (char target-string match-start))))) (regex-replace-all url-regex string #'convert)))) Converted URL-ENCODE. URL-ENCODE * (url-encode "Fête Sørensen naïve Hühner Straße") "F%EAte%20S%F8rensen%20na%EFve%20H%FChner%20Stra%DFe" T * (defun how-many (target-string start end match-start match-end reg-starts reg-ends) (declare (ignore start end match-start match-end)) (format nil "~A" (- (svref reg-ends 0) (svref reg-starts 0)))) HOW-MANY * (regex-replace-all "{(.+?)}" "foo{...}bar{.....}{..}baz{....}frob" (list "[" 'how-many " dots]")) "foo[3 dots]bar[5 dots][2 dots]baz[4 dots]frob" T * (let ((qp-regex (create-scanner "[\\x80-\\xff]"))) (defun encode-quoted-printable (string) "Converts 8-bit string to quoted-printable representation. Version using SIMPLE-CALLS keyword argument." ;; ;; won't work for Corman Lisp because non-ASCII characters aren't 8-bit there (flet ((convert (match) (format nil "=~2,'0x" (char-code (char match 0))))) (regex-replace-all qp-regex string #'convert :simple-calls t)))) Converted ENCODE-QUOTED-PRINTABLE. ENCODE-QUOTED-PRINTABLE * (encode-quoted-printable "Fête Sørensen naïve Hühner Straße") "F=EAte S=F8rensen na=EFve H=FChner Stra=DFe" T * (defun how-many (match first-register) (declare (ignore match)) (format nil "~A" (length first-register))) HOW-MANY * (regex-replace-all "{(.+?)}" "foo{...}bar{.....}{..}baz{....}frob" (list "[" 'how-many " dots]") :simple-calls t) "foo[3 dots]bar[5 dots][2 dots]baz[4 dots]frob" T
[Special variable]
*property-resolver*
This is the designator for a function responsible for resolving named properties like\p{Number}
. If CL-PPCRE encounters a\p
or a\P
it expects to see an opening curly brace immediately afterwards and will then read everything following that brace until it sees a closing curly brace. The resolver function will be called with this string and must return a corresponding unary test function which accepts a character as its argument and returns a true value if and only if the character has the named property. If the resolver returnsNIL
instead, it signals that a property of that name is unknown.* (labels ((char-code-odd-p (char) (oddp (char-code char))) (char-code-even-p (char) (evenp (char-code char))) (resolver (name) (cond ((string= name "odd") #'char-code-odd-p) ((string= name "even") #'char-code-even-p) ((string= name "true") (constantly t)) (t (error "Can't resolve ~S." name))))) (let ((*property-resolver* #'resolver)) ;; quiz question - why do we need CREATE-SCANNER here? (list (regex-replace-all (create-scanner "\\p{odd}") "abcd" "+") (regex-replace-all (create-scanner "\\p{even}") "abcd" "+") (regex-replace-all (create-scanner "\\p{true}") "abcd" "+")))) ("+b+d" "a+c+" "++++")If the value of*PROPERTY-RESOLVER*
isNIL
(which is the default),\p
and\P
in regex strings will simply be treated likep
orP
as in CL-PPCRE 1.4.1 and earlier. Note that this does not affect the validity of(:PROPERTY <name>)
parts in S-expression syntax.
[Accessor]
parse-tree-synonym symbol => parse-tree
(setf (parse-tree-synonym symbol) new-parse-tree)
Any symbol (unless it's a keyword with a special meaning in parse trees) can be made a "synonym", i.e. an abbreviation, for another parse tree by this accessor.PARSE-TREE-SYNONYM
returnsNIL
ifsymbol
isn't a synonym yet.* (parse-string "a*b+") (:SEQUENCE (:GREEDY-REPETITION 0 NIL #\a) (:GREEDY-REPETITION 1 NIL #\b)) * (defun my-repetition (char min) `(:greedy-repetition ,min nil ,char)) MY-REPETITION * (setf (parse-tree-synonym 'a*) (my-repetition #\a 0)) (:GREEDY-REPETITION 0 NIL #\a) * (setf (parse-tree-synonym 'b+) (my-repetition #\b 1)) (:GREEDY-REPETITION 1 NIL #\b) * (let ((scanner (create-scanner '(:sequence a* b+)))) (dolist (string '("ab" "b" "aab" "a" "x")) (print (scan scanner string))) (values)) 0 0 0 NIL NIL * (parse-tree-synonym 'a*) (:GREEDY-REPETITION 0 NIL #\a) * (parse-tree-synonym 'a+) NIL
[Macro]
define-parse-tree-synonym name parse-tree => parse-tree
This is a convenience macro for parse tree synonyms defined as(defmacro define-parse-tree-synonym (name parse-tree) `(eval-when (:compile-toplevel :load-toplevel :execute) (setf (parse-tree-synonym ',name) ',parse-tree)))so you can write code like this:(define-parse-tree-synonym a-z (:char-class (:range #\a #\z) (:range #\A #\Z))) (define-parse-tree-synonym a-z* (:greedy-repetition 0 nil a-z)) (defun ascii-char-tester (string) (scan '(:sequence :start-anchor a-z* :end-anchor) string))
[Special variable]
*regex-char-code-limit*
This variable controls whether scanners take into account all characters of your CL implementation or only those theCHAR-CODE
of which is not larger than its value. The default isCHAR-CODE-LIMIT
, and you might see significant speed and space improvements during scanner creation if, say, your target strings only contain ISO-8859-1 characters and you're using a Lisp implementation whereCHAR-CODE-LIMIT
has a value much higher than 256. The test suite will automatically set*REGEX-CHAR-CODE-LIMIT*
to 256 while you're running the default test.Note: Due to the nature of
LOAD-TIME-VALUE
and the compiler macro forSCAN
and other functions, some scanners might be created in a null lexical environment at load time or at compile time so be careful to which value*REGEX-CHAR-CODE-LIMIT*
is bound at that time. The default value should always yield correct results unless you play dirty tricks with implementation-dependent behaviour, though.
[Special variable]
*use-bmh-matchers*
Usually, the scanners created byCREATE-SCANNER
(or implicitly by other functions and macros) will use the standard functionSEARCH
to check for constant strings at the start or end of the regular expression. If*USE-BMH-MATCHERS*
is true (the default isNIL
), fast Boyer-Moore-Horspool matchers will be used instead. This will usually be faster but can make the scanners considerably bigger. Per BMH matcher - there can be up to two per scanner - a fixnum array of size*REGEX-CHAR-CODE-LIMIT*
is allocated and closed over.Note: Due to the nature of
LOAD-TIME-VALUE
and the compiler macro forSCAN
and other functions, some scanners might be created in a null lexical environment at load time or at compile time so be careful to which value*USE-BMH-MATCHERS*
is bound at that time.
[Special variable]
*optimize-char-classes*
Whether character classes should be compiled into look-ups into O(1) data structures. This is usually fast but will be costly in terms of scanner creation time and might be costly in terms of size if*REGEX-CHAR-CODE-LIMIT*
is high. This value will be used as thekind
keyword argument toCREATE-OPTIMIZED-TEST-FUNCTION
- see there for the possible non-NIL
values. The default value (NIL
) should usually be fine unless you're sure that you absolutely have to optimize some character classes for speed.Note: Due to the nature of
LOAD-TIME-VALUE
and the compiler macro forSCAN
and other functions, some scanners might be created in a null lexical environment at load time or at compile time so be careful to which value*OPTIMIZE-CHAR-CLASSES*
is bound at that time.
[Special variable]
*allow-quoting*
If this value is true (the default isNIL
), CL-PPCRE will support\Q
and\E
in regex strings to quote (disable) metacharacters. Note that this entails a slight performance penalty when creating scanners because (a copy of) the regex string is modified (probably more than once) before it is fed to the parser. Also, the parser's syntax error messages will complain about the converted string and not about the original regex string.* (scan "^a+$" "a+") NIL * (let ((*allow-quoting* t)) ;;we use CREATE-SCANNER because of Lisps like SBCL that don't have an interpreter (scan (create-scanner "^\\Qa+\\E$") "a+")) 0 2 #() #() * (let ((*allow-quoting* t)) (scan (create-scanner "\\Qa()\\E(?#comment\\Q)a**b") "()ab")) Quantifier '*' not allowed at position 19 in string "a\\(\\)(?#commentQ)a**b"Note how in the last example the regex string in the error message is different from the first argument to theSCAN
function. Also note that the second example might be easier to understand (and Lisp-ier) if you write it like this:* (scan '(:sequence :start-anchor "a+" ;; no quoting necessary :end-anchor) "a+") 0 2 #() #()Make sure you also read the relevant section in "Bugs and problems."Note: Due to the nature of
LOAD-TIME-VALUE
and the compiler macro forSCAN
and other functions, some scanners might be created in a null lexical environment at load time or at compile time so be careful to which value*ALLOW-QUOTING*
is bound at that time.
[Special variable]
*allow-named-registers*
If this value is true (the default isNIL
), CL-PPCRE will support(?<name>"<regex>")
and\k<name>
in regex strings to provide named registers and back-references as in AllegroCL.name
is has to start with a letter and can contain only alphanumeric characters or minus sign. Names of registers are matched case-sensitively. The parse tree syntax is not affected by the*ALLOW-NAMED-REGISTERS*
switch,:NAMED-REGISTER
and:BACK-REFERENCE
forms are always resolved as expected. There are also no restrictions on register names in this syntax except that they have to be strings.;; Perl compatible mode (*ALLOW-NAMED-REGISTERS* is NIL) * (create-scanner "(?<reg>.*)") Character 'r' may not follow '(?<' at position 3 in string "(?<reg>)" ;; just unescapes "\\k" * (parse-string "\\k<reg>") "k<reg>" * (setq *allow-named-registers* t) T * (create-scanner "((?<small>[a-z]*)(?<big>[A-Z]*))") #<CLOSURE (LAMBDA (STRING CL-PPCRE::START CL-PPCRE::END)) {AD75BFD}> (NIL "small" "big") ;; the scanner doesn't capture any information about named groups - ;; you have to store the second value returned from CREATE-SCANNER yourself * (scan * "aaaBBB") 0 6 #(0 0 3) #(6 3 6) ;; parse tree syntax * (parse-string "((?<small>[a-z]*)(?<big>[A-Z]*))") (:REGISTER (:SEQUENCE (:NAMED-REGISTER "small" (:GREEDY-REPETITION 0 NIL (:CHAR-CLASS (:RANGE #\a #\z)))) (:NAMED-REGISTER "big" (:GREEDY-REPETITION 0 NIL (:CHAR-CLASS (:RANGE #\A #\Z)))))) * (create-scanner *) #<CLOSURE (LAMBDA (STRING CL-PPCRE::START CL-PPCRE::END)) {B158E3D}> (NIL "small" "big") ;; multiple-choice back-reference * (scan "^(?<reg>[ab])(?<reg>[12])\\k<reg>\\k<reg>$" "a1aa") 0 4 #(0 1) #(1 2) * (scan "^(?<reg>[ab])(?<reg>[12])\\k<reg>\\k<reg>$" "a22a") 0 4 #(0 1) #(1 2) ;; demonstrating most-recently-seen-register-first property of back-reference; ;; "greedy" regex (analogous to "aa?") * (scan "^(?<reg>)(?<reg>a)(\\k<reg>)" "a") 0 1 #(0 0 1) #(0 1 1) * (scan "^(?<reg>)(?<reg>a)(\\k<reg>)" "aa") 0 2 #(0 0 1) #(0 1 2) ;; switched groups ;; "lazy" regex (analogous to "aa??") * (scan "^(?<reg>a)(?<reg>)(\\k<reg>)" "a") 0 1 #(0 1 1) #(1 1 1) ;; scanner ignores the second "a" * (scan "^(?<reg>a)(?<reg>)(\\k<reg>)" "aa") 0 1 #(0 1 1) #(1 1 1) ;; "aa" will be matched only when forced by adding "$" at the end * (scan "^(?<reg>a)(?<reg>)(\\k<reg>)$" "aa") 0 2 #(0 1 1) #(1 1 2)Note: Due to the nature ofLOAD-TIME-VALUE
and the compiler macro forSCAN
and other functions, some scanners might be created in a null lexical environment at load time or at compile time so be careful to which value*ALLOW-NAMED-REGISTERS*
is bound at that time.
[Function]
parse-string string => parse-tree
Converts the regex stringstring
into a parse tree. Note that the result is usually one possible way of creating an equivalent parse tree and not necessarily the "canonical" one. Specifically, the parse tree might contain redundant parts which are supposed to be excised when a scanner is created.
[Function]
create-optimized-test-function test-function &key start end kind => function
Given a unary test functiontest-function
which is applicable to characters returns a function which yields the same boolean results for all characters with character codes fromstart
to (excluding)end
. Ifkind
isNIL
,test-function
will simply be returned. Otherwise,kind
should be one of:You can also use
:HASH-TABLE
- The function builds a hash table representing all characters which satisfy the test and returns a closure which checks if a character is in that hash table.
:CHARSET
- Instead of a hash table the function uses a "charset" which is a data structure using non-linear hashing and optimized to represent (sparse) sets of characters in a fast and space-efficient way (contributed by Nikodemus Siivola).
:CHARMAP
- Instead of a hash table the function uses a bit vector to represent the set of characters.
:HASH-TABLE*
or:CHARSET*
which are like:HASH-TABLE
and:CHARSET
but use the complement of the set if the set contains more than half of all characters betweenstart
andend
. This saves space but needs an additional pass across all characters to create the data structure. There is no corresponding:CHARMAP*
kind
as the bit vectors are already created to cover the smallest possible interval which contains either the set or its complement.See also
*OPTIMIZE-CHAR-CLASSES*
.
[Function]
quote-meta-chars string => string'
This is a simple utility function used when*ALLOW-QUOTING*
is true. It returns a stringSTRING'
where all non-word characters (everything except ASCII characters, digits and underline) ofSTRING
are quoted by prepending a backslash similar to Perl'squotemeta
function. It always returns a fresh string.* (quote-meta-chars "[a-z]*") "\\[a\\-z\\]\\*"
[Function]
regex-apropos regex &optional packages &key case-insensitive => list
LikeAPROPOS
but searches for interned symbols which match the regular expressionregex
. The output is implementation-dependent. Ifcase-insensitive
is true (which is the default) andregex
isn't already a scanner, a case-insensitive scanner is used.Here are examples for CMUCL:
* *package* #<The COMMON-LISP-USER package, 16/21 internal, 0/9 external> * (defun foo (n &optional (k 0)) (+ 3 n k)) FOO * (defparameter foo "bar") FOO * (defparameter |foobar| 42) |foobar| * (defparameter fooboo 43) FOOBOO * (defclass frobar () ()) #<STANDARD-CLASS FROBAR {4874E625}> * (regex-apropos "foo(?:bar)?") FOO [variable] value: "bar" [compiled function] (N &OPTIONAL (K 0)) FOOBOO [variable] value: 43 |foobar| [variable] value: 42 * (regex-apropos "(?:foo|fro)bar") PCL::|COMMON-LISP-USER::FROBAR class predicate| [compiled closure] FROBAR [class] #<STANDARD-CLASS FROBAR {4874E625}> |foobar| [variable] value: 42 * (regex-apropos "(?:foo|fro)bar" 'cl-user) FROBAR [class] #<STANDARD-CLASS FROBAR {4874E625}> |foobar| [variable] value: 42 * (regex-apropos "(?:foo|fro)bar" '(pcl ext)) PCL::|COMMON-LISP-USER::FROBAR class predicate| [compiled closure] * (regex-apropos "foo") FOO [variable] value: "bar" [compiled function] (N &OPTIONAL (K 0)) FOOBOO [variable] value: 43 |foobar| [variable] value: 42 * (regex-apropos "foo" nil :case-insensitive nil) |foobar| [variable] value: 42
[Function]
regex-apropos-list regex &optional packages &key upcase => list
LikeAPROPOS-LIST
but searches for interned symbols which match the regular expressionregex
. Ifcase-insensitive
is true (which is the default) andregex
isn't already a scanner, a case-insensitive scanner is used.Example (continued from above):
* (regex-apropos-list "foo(?:bar)?") (|foobar| FOOBOO FOO)
[Condition type]
ppcre-error
Every error signaled by CL-PPCRE is of typePPCRE-ERROR
. This is a direct subtype ofSIMPLE-ERROR
without any additional slots or options.
[Condition type]
ppcre-invocation-error
Errors of typePPCRE-INVOCATION-ERROR
are signaled if one of the exported functions of CL-PPCRE is called with wrong or inconsistent arguments. This is a direct subtype ofPPCRE-ERROR
without any additional slots or options.
[Condition type]
ppcre-syntax-error
An error of typePPCRE-SYNTAX-ERROR
is signaled if CL-PPCRE's parser encounters an error when trying to parse a regex string or to convert a parse tree into its internal representation. This is a direct subtype ofPPCRE-ERROR
with two additional slots. These denote the regex string which HTML-PPCRE was parsing and the position within the string where the error occurred. If the error happens while CL-PPCRE is converting a parse tree, both of these slots containNIL
. (See the next two entries on how to access these slots.)As many syntax errors can't be detected before the parser is at the end of the stream, the row and column usually denote the last position where the parser was happy and not the position where it gave up.
* (handler-case (scan "foo**x" "fooox") (ppcre-syntax-error (condition) (format t "Houston, we've got a problem with the string ~S:~%~ Looks like something went wrong at position ~A.~%~ The last message we received was \"~?\"." (ppcre-syntax-error-string condition) (ppcre-syntax-error-pos condition) (simple-condition-format-control condition) (simple-condition-format-arguments condition)) (values))) Houston, we've got a problem with the string "foo**x": Looks like something went wrong at position 4. The last message we received was "Quantifier '*' not allowed.".
[Function]
ppcre-syntax-error-string condition => string
Ifcondition
is a condition of typePPCRE-SYNTAX-ERROR
, this function will return the string the parser was parsing when the error was encountered (orNIL
if the error happened while trying to convert a parse tree). This might be particularly useful when*ALLOW-QUOTING*
is true because in this case the offending string might not be the one you gave to theCREATE-SCANNER
function.
[Function]
ppcre-syntax-error-pos condition => number
Ifcondition
is a condition of typePPCRE-SYNTAX-ERROR
, this function will return the position within the string where the error occurred (orNIL
if the error happened while trying to convert a parse tree).
(asdf:oos 'asdf:load-op :cl-ppcre-unicode)This will automatically install
UNICODE-PROPERTY-RESOLVER
as your property resolver.
See the CL-UNICODE documentation for information about the supported Unicode properties and how they are named.
[Function]
unicode-property-resolver property-name => function-or-nil
A property resolver which understands Unicode properties using CL-UNICODE'sPROPERTY-TEST
function. This resolver is automatically installed in*PROPERTY-RESOLVER*
when the CL-PPCRE-UNICODE system is loaded.* (scan-to-strings "\\p{Script:Latin}+" "0+AB_*") "AB" #()Note that this symbol is exported from theCL-PPCRE-UNICODE
package and not from theCL-PPCRE
package.
A filter is defined by its filter function which must be a
function of one argument. During the parsing process this function
might be called once or several times or it might not be called at
all. If it's called, its argument is an integer pos
which is the current position within the target string. The filter can
either return NIL
(which means that the subexpression
represented by this filter didn't match) or an integer not smaller
than pos
for success. A zero-length assertion
should return pos
itself while a filter which
wants to consume N
characters should return
(+ POS N)
.
If you supply the optional value length
and it is
not NIL
, then this is a promise to the regex engine that
your filter will always consume exactly
length
characters. The regex engine might use this
information for optimization purposes but it is otherwise irrelevant
to the outcome of the matching process.
The filter function can access the following special variables from its code body:
CL-PPCRE::*STRING*
CL-PPCRE::*START-POS*
and
CL-PPCRE::*END-POS*
START
and END
keyword parameters
of SCAN
.CL-PPCRE::*REAL-START-POS*
DO-SCANS
) where
CL-PPCRE::*START-POS*
will be moved forward while
CL-PPCRE::*REAL-START-POS*
won't. For normal scans the
value of this variable is NIL
.CL-PPCRE::*REG-STARTS*
and
CL-PPCRE::*REG-ENDS*
CL-PPCRE::*REG-STARTS*
is
NIL
.
Note that the names of the variables are not exported from the
CL-PPCRE
package because there's no explicit guarantee
that they will be available in future releases. (Although after so
many years it is very unlikely that they'll go away...)
* (defun my-info-filter (pos) "Show some info about the matching process." (format t "Called at position ~A~%" pos) (loop with dim = (array-dimension cl-ppcre::*reg-starts* 0) for i below dim for reg-start = (aref cl-ppcre::*reg-starts* i) for reg-end = (aref cl-ppcre::*reg-ends* i) do (format t "Register ~A is currently " (1+ i)) when reg-start (write-string cl-ppcre::*string* nil do (write-char #\') (write-string cl-ppcre::*string* nil :start reg-start :end reg-end) (write-char #\') else do (write-string "unbound") do (terpri)) (terpri) pos) MY-INFO-FILTER * (scan '(:sequence (:register (:greedy-repetition 0 nil (:char-class (:range #\a #\z)))) (:filter my-info-filter 0) "X") "bYcdeX") Called at position 1 Register 1 is currently 'b' Called at position 0 Register 1 is currently '' Called at position 1 Register 1 is currently '' Called at position 5 Register 1 is currently 'cde' 2 6 #(2) #(5) * (scan '(:sequence (:register (:greedy-repetition 0 nil (:char-class (:range #\a #\z)))) (:filter my-info-filter 0) "X") "bYcdeZ") NIL * (defun my-weird-filter (pos) "Only match at this point if either pos is odd and the character we're looking at is lowercase or if pos is even and the next two characters we're looking at are uppercase. Consume these characters if there's a match." (format t "Trying at position ~A~%" pos) (cond ((and (oddp pos) (< pos cl-ppcre::*end-pos*) (lower-case-p (char cl-ppcre::*string* pos))) (1+ pos)) ((and (evenp pos) (< (1+ pos) cl-ppcre::*end-pos*) (upper-case-p (char cl-ppcre::*string* pos)) (upper-case-p (char cl-ppcre::*string* (1+ pos)))) (+ pos 2)) (t nil))) MY-WEIRD-FILTER * (defparameter *weird-regex* `(:sequence "+" (:filter ,#'my-weird-filter) "+")) *WEIRD-REGEX* * (scan *weird-regex* "+A++a+AA+") Trying at position 1 Trying at position 3 Trying at position 4 Trying at position 6 5 9 #() #() * (fmakunbound 'my-weird-filter) MY-WEIRD-FILTER * (scan *weird-regex* "+A++a+AA+") Trying at position 1 Trying at position 3 Trying at position 4 Trying at position 6 5 9 #() #()Note that in the second call to
SCAN
our filter wasn't
invoked at all - it was optimized away by the regex engine because it
knew that it couldn't match. Also note that *WEIRD-REGEX*
still worked after we removed the global function definition of
MY-WEIRD-FILTER
because the regular expression had
captured the original definition.
For more ideas about what you can do with filters see this
thread on the mailing list.
undef
in $1
, $2
, etc.perltestdata
.)
This is a
bug in Perl 5.6.1 and earlier which has been fixed in 5.8.0.
perltestdata
.)
This is a
bug in Perl 5.6.1 and earlier which has been fixed in 5.8.0.
$1
, $2
, etc.perltestdata
.)
This is a
bug in Perl which hasn't been fixed yet.
perltestdata
.)
Well, OK, this ain't a Perl bug. I just can't quite understand why
captured groups should only be seen within the scope of a look-ahead
or look-behind. For the moment, CL-PPCRE and Perl agree to
disagree... :)
perltestdata
.) I
also think this a Perl bug but I currently have lost the drive to
report it.
"\r"
doesn't work with MCLperltestdata
.) For
some strange reason that I don't understand MCL translates
#\Return
to (CODE-CHAR 10)
while MacPerl
translates "\r"
to (CODE-CHAR
13)
. Hmmm...
"\w"
?ALPHANUMERICP
to decide whether a character matches Perl's
"\w"
, so depending on your CL implementation
you might encounter differences between Perl and CL-PPCRE when
matching non-ASCII characters.
"\Q"
doesn't work, or does it?1
.
#!/usr/bin/perl -l $a = '\E*'; print 1 if '\E*\E*' =~ /(?:\Q$a\E){2}/;If you try to do something similar in CL-PPCRE, you get an error:
* (let ((*allow-quoting* t) (a "\\E*")) (scan (concatenate 'string "(?:\\Q" a "\\E){2}") "\\E*\\E*")) Quantifier '*' not allowed at position 3 in string "(?:*\\E){2}"The error message might give you a hint as to why this happens: Because
*ALLOW-QUOTING*
was true the concatenated string was pre-processed before it
was fed to CL-PPCRE's parser - the result of this pre-processing is
"(?:*\\E){2}"
because the
"\\E"
in the string A
was taken to
be the end of the quoted section started by
"\\Q"
. This cannot happen in Perl due to its
complicated interpolation rules - see man perlop
for
the scary details. It can happen in CL-PPCRE, though.
Bummer!
What gives? "\\Q...\\E"
in CL-PPCRE should only
be used in literal strings. If you want to quote arbitrary strings,
try CL-INTERPOL or use QUOTE-META-CHARS
:
* (let ((a "\\E*")) (scan (concatenate 'string "(?:" (quote-meta-chars a) "){2}") "\\E*\\E*")) 0 6 #() #()Or, even better and Lisp-ier, use the S-expression syntax instead - no need for quoting in this case:
* (let ((a "\\E*")) (scan `(:greedy-repetition 2 2 ,a) "\\E*\\E*")) 0 6 #() #()
* (let ((a "y\\y")) (scan a a)) NILYou didn't expect this to yield
NIL
, did you? Shouldn't something like (SCAN A A)
always return a true value? No, because the first and the second argument to SCAN
are handled differently: The first argument is fed to CL-PPCRE's parser and is treated like a Perl regular expression. In particular, the parser "sees" \y
and converts it to y
because \y
has no special meaning in regular expressions. So, the regular expression is the constant string "yy"
. But the second argument isn't converted - it is left as is, i.e. it's equivalent to Perl's 'y\y'
. In other words, this example would be equivalent to the Perl code
'y\y' =~ /y\y/;or to
$a = 'y\y'; $a =~ /$a/;which should explain why it doesn't match.
Still confused? You might want to try CL-INTERPOL.
CREATE-SCANNER
and SCAN
are dispatched to their AllegroCL
counterparts EXCL:COMPILE-RE
and EXCL:MATCH-RE
while everything else is left as is.)
The advantage of this mode is that you'll get a much smaller image and most likely faster code. (But note that CL-PPCRE needs to do a small amount of work to massage AllegroCL's output into the format expected by CL-PPCRE.) The downside is that your code won't be fully compatible with CL-PPCRE anymore. Here are some of the differences (most of which probably don't matter very often):
:CASE-INSENSITIVE
keyword parameter) is currently only effective for ASCII characters.
CREATE-SCANNER
) aren't functions but structures.
To use the AllegroCL compatibility mode you have to
(push :use-acl-regexp2-engine *features*)before you compile CL-PPCRE.
CL-USER 1 > (scan-to-strings "<=|<" "<=") "<=" #() CL-USER 2 > (scan-to-strings "<|<=" "<=") "<" #()
(defun regex-match (regex target) ;; don't do that! (scan regex target))
SCAN
will usually be faster
than Common
Lisp's SEARCH
if you use BMH matchers. However,
this only makes sense if scanner creation time is not the
limiting factor, i.e. if the search target is very large or
if you're using the same scanner very often.
*USE-BMH-MATCHERS*
together with a large value for
*REGEX-CHAR-CODE-LIMIT*
can lead to huge scanners.
"[af-l\\d]"
means to test if the character is
equal to #\a
, then to test if it's
between #\f
and #\l
, then if it's a digit.
There's by default no attempt to remove redundancy (as
in "[a-ge-kf]"
) or to otherwise optimize these tests
for speed. However, you can play
with *OPTIMIZE-CHAR-CLASSES*
if you've identified character classes as a bottleneck and want to
make sure that you have O(1) test functions.
"(a-d|aebf)"
and "ab(cd|ef)"
are equivalent, but only the second
form has a constant start the regex engine can recognize.
(let ((target (make-string 10000 :initial-element #\a)) (scanner-1 (create-scanner "a*\\d")) (scanner-2 (create-scanner "(?>a*)\\d"))) (time (scan scanner-1 target)) (time (scan scanner-2 target)))
"(?:foo)"
instead of
"(foo)"
whenever possible.)
"([a-c])+"
and "[a-c]*([a-c])"
have
exactly the same semantics but completely different performance
characteristics. (Actually, in some cases CL-PPCRE automatically
converts expressions from the first type into the second type.
That's not always possible, though, and you shouldn't rely on it.)
use re "debug"
pragma
have been very helpful in optimizing the scanners created by CL-PPCRE.
The list of people who participated in this project in one way or the other has grown too long to maintain it here. See the ChangeLog for all the people who helped with patches, bug reports, or in other ways. Thanks to all of them!
Thanks to the guys at "Café Olé" in Hamburg where I wrote most of the 0.1.0 release and thanks to my wife for lending me her PowerBook to test early versions of CL-PPCRE with MCL and OpenMCL.
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