$1 is 'A', $2 is 'C' and $3 is 'B' and $4 is 'D' that a .NET programmer
would expect. This is considered a feature. :-)
+=item Possessive Quantifiers
+
+Perl now supports the "possessive quantifier" syntax of the "atomic match"
+pattern. Basically a possessive quantifier matches as much as it can and never
+gives any back. Thus it can be used to control backtracking. The syntax is
+similar to non-greedy matching, except instead of using a '?' as the modifier
+the '+' is used. Thus C<?+>, C<*+>, C<++>, C<{min,max}+> are now legal
+quantifiers.
+
=back
=head1 Modules and Pragmas
{n,}? Match at least n times
{n,m}? Match at least n but not more than m times
+By default, when a quantified subpattern does not allow the rest of the
+overall pattern to match, Perl will backtrack. However, this behaviour is
+sometimes undesirable. Thus Perl provides the "possesive" quantifier form
+as well.
+
+ *+ Match 0 or more times and give nothing back
+ +? Match 1 or more times and give nothing back
+ ?+ Match 0 or 1 time and give nothing back
+ {n}+ Match exactly n times and give nothing back (redundant)
+ {n,}? Match at least n times and give nothing back
+ {n,m}? Match at least n but not more than m times and give nothing back
+
+For instance,
+
+ 'aaaa' =~ /a++a/
+
+will never match, as the C<a++> will gobble up all the C<a>'s in the
+string and won't leave any for the remaining part of the pattern. This
+feature can be extremely useful to give perl hints about where it
+shouldn't backtrack. For instance, the typical "match a double-quoted
+string" problem can be most efficiently performed when written as:
+
+ /"(?:[^"\\]++|\\.)*+"/
+
+as we know that if the final quote does not match, bactracking will not
+help. See the independent subexpression C<< (?>...) >> for more details;
+possessive quantifiers are just syntactic sugar for that construct. For
+instance the above example could also be written as follows:
+
+ /"(?>(?:(?>[^"\\]+)|\\.)*)"/
+
Because patterns are processed as double quoted strings, the following
also work:
X<\t> X<\n> X<\r> X<\f> X<\a> X<\l> X<\u> X<\L> X<\U> X<\E> X<\Q>
X<(?{})> X<regex, code in> X<regexp, code in> X<regular expression, code in>
B<WARNING>: This extended regular expression feature is considered
-highly experimental, and may be changed or deleted without notice.
+experimental, and may be changed without notice. Code executed that
+has side effects may not perform identically from version to version
+due to the effect of future optimisations in the regex engine.
This zero-width assertion evaluates any embedded Perl code. It
always succeeds, and its C<code> is not interpolated. Currently,
X<regex, postponed> X<regexp, postponed> X<regular expression, postponed>
B<WARNING>: This extended regular expression feature is considered
-highly experimental, and may be changed or deleted without notice.
-A simplified version of the syntax may be introduced for commonly
-used idioms.
+experimental, and may be changed without notice. Code executed that
+has side effects may not perform identically from version to version
+due to the effect of future optimisations in the regex engine.
This is a "postponed" regular subexpression. The C<code> is evaluated
at run time, at the moment this subexpression may match. The result
X<(?PARNO)> X<(?1)> X<(?R)> X<(?0)>
X<regex, recursive> X<regexp, recursive> X<regular expression, recursive>
-B<WARNING>: This extended regular expression feature is considered
-highly experimental, and may be changed or deleted without notice.
-
Similar to C<(??{ code })> except it does not involve compiling any code,
instead it treats the contents of a capture buffer as an independent
pattern that must match at the current position. Capture buffers
=item C<< (?>pattern) >>
X<backtrack> X<backtracking> X<atomic> X<possessive>
-B<WARNING>: This extended regular expression feature is considered
-highly experimental, and may be changed or deleted without notice.
-
An "independent" subexpression, one which matches the substring
that a I<standalone> C<pattern> would match if anchored at the given
position, and it matches I<nothing other than this substring>. This
In some literature this construct is called "atomic matching" or
"possessive matching".
+Possessive quantifiers are equivalent to putting the item they are applied
+to inside of one of these constructs. The following equivalences apply:
+
+ Quantifier Form Bracketing Form
+ --------------- ---------------
+ PAT*+ (?>PAT*)
+ PAT++ (?>PAT+)
+ PAT?+ (?>PAT?)
+ PAT{min,max}+ (?>PAT{min,max})
+
=item C<(?(condition)yes-pattern|no-pattern)>
X<(?()>
=item C<(?(condition)yes-pattern)>
-B<WARNING>: This extended regular expression feature is considered
-highly experimental, and may be changed or deleted without notice.
-
Conditional expression. C<(condition)> should be either an integer in
parentheses (which is valid if the corresponding pair of parentheses
matched), a look-ahead/look-behind/evaluate zero-width assertion, a
This will allow the use of a regex from inside (?{ }), (??{ }) and
(?(?{ })|) constructs.
-=head2 Add possessive quantifiers to regexp engine
-
-Possessive quantifiers are a syntactic sugar that affords a more
-elegant way to express (?>A+). They are also provided by many other
-regex engines. Most importantly they allow various patterns to be
-optimised more efficiently than (?>...) allows, and allow various data
-driven optimisations to be implemented (such as auto-possesification of
-quantifiers followed by contrary suffixes). Common syntax for them is
-
- ++ possessive 1 or more
- *+ possessive 0 or more
- {n,m}+ possessive n..m
-
-A possessive quantifier basically absorbs as much as it can and doesn't
-give any back.
-
-Jeffrey Friedl documents possessive quantifiers in Mastering Regular
-Expressions 2nd edition and explicitly pleads for them to be added to
-perl. We should oblige him, lest he leaves us out of a future edition.
-;-)
-
-demerphq has this on his todo list
-
=head2 Add (?YES) (?NO) to regexp enigne
YES/NO would allow a subpattern to be passed/failed but allow backtracking.
* Beware that the optimization-preparation code in here knows about some
* of the structure of the compiled regexp. [I'll say.]
*/
+
+
+
#ifndef PERL_IN_XSUB_RE
-#define CORE_ONLY_BLOCK(c) {c}{
#define RE_ENGINE_PTR &PL_core_reg_engine
#else
-#define CORE_ONLY_BLOCK(c) {
extern const struct regexp_engine my_reg_engine;
#define RE_ENGINE_PTR &my_reg_engine
#endif
+/* these make a few things look better, to avoid indentation */
+#define BEGIN_BLOCK {
#define END_BLOCK }
regexp *
dVAR;
GET_RE_DEBUG_FLAGS_DECL;
DEBUG_r(if (!PL_colorset) reginitcolors());
- CORE_ONLY_BLOCK(
+#ifndef PERL_IN_XSUB_RE
+ BEGIN_BLOCK
/* Dispatch a request to compile a regexp to correct
regexp engine. */
HV * const table = GvHV(PL_hintgv);
});
return CALLREGCOMP_ENG(eng, exp, xend, pm);
}
- })
+ }
+ END_BLOCK
+#endif
+ BEGIN_BLOCK
register regexp *r;
regnode *scan;
regnode *first;
*flagp = flags;
return(ret);
}
- /* else if (OP(ret)==RECURSE) {
- RExC_parse++;
- vFAIL("Illegal quantifier on recursion group");
- } */
#if 0 /* Now runtime fix should be reliable. */
origparse);
}
- if (*RExC_parse == '?') {
+ if (RExC_parse < RExC_end && *RExC_parse == '?') {
nextchar(pRExC_state);
reginsert(pRExC_state, MINMOD, ret, depth+1);
REGTAIL(pRExC_state, ret, ret + NODE_STEP_REGNODE);
}
- if (ISMULT2(RExC_parse)) {
+#ifndef REG_ALLOW_MINMOD_SUSPEND
+ else
+#endif
+ if (RExC_parse < RExC_end && *RExC_parse == '+') {
+ regnode *ender;
+ nextchar(pRExC_state);
+ ender = reg_node(pRExC_state, SUCCEED);
+ REGTAIL(pRExC_state, ret, ender);
+ reginsert(pRExC_state, SUSPEND, ret, depth+1);
+ ret->flags = 0;
+ ender = reg_node(pRExC_state, TAIL);
+ REGTAIL(pRExC_state, ret, ender);
+ /*ret= ender;*/
+ }
+
+ if (RExC_parse < RExC_end && ISMULT2(RExC_parse)) {
RExC_parse++;
vFAIL("Nested quantifiers");
}
#define PERL_ENABLE_EXTENDED_TRIE_OPTIMISATION 1
#define PERL_ENABLE_POSITIVE_ASSERTION_STUDY 1
#define PERL_ENABLE_EXPERIMENTAL_REGEX_OPTIMISATIONS 0
+/* Unless the next line is uncommented it is illegal to combine lazy
+ matching with possessive matching. Frankly it doesn't make much sense
+ to allow it as X*?+ matches nothing, X+?+ matches a single char only,
+ and X{min,max}?+ matches min times only.
+ */
+/* #define REG_ALLOW_MINMOD_SUSPEND */
/*
* The "internal use only" fields in regexp.h are present to pass info from
/(ab)+((?1))(fox)/ ababfox y $1-$2-$3 ab-ab-fox
/(ab){1,100}((?1))(fox)/ ababfox y $1-$2-$3 ab-ab-fox
/(ab){0,100}((?1))(fox)/ ababfox y $1-$2-$3 ab-ab-fox
+# possessive captures
+a++a aaaaa n - -
+a*+a aaaaa n - -
+a{1,5}+a aaaaa n - -
+a?+a ab n - -
+a++b aaaaab y $& aaaaab
+a*+b aaaaab y $& aaaaab
+a{1,5}+b aaaaab y $& aaaaab
+a?+b ab y $& ab
+fooa++a fooaaaaa n - -
+fooa*+a fooaaaaa n - -
+fooa{1,5}+a fooaaaaa n - -
+fooa?+a fooab n - -
+fooa++b fooaaaaab y $& fooaaaaab
+fooa*+b fooaaaaab y $& fooaaaaab
+fooa{1,5}+b fooaaaaab y $& fooaaaaab
+fooa?+b fooab y $& fooab
+(?:aA)++(?:aA) aAaAaAaAaA n - aAaAaAaAaA
+(aA)++(aA) aAaAaAaAaA n - aAaAaAaAaA
+(aA|bB)++(aA|bB) aAaAbBaAbB n - aAaAbBaAbB
+(?:aA|bB)++(?:aA|bB) aAbBbBbBaA n - aAbBbBbBaA
+(?:aA)*+(?:aA) aAaAaAaAaA n - aAaAaAaAaA
+(aA)*+(aA) aAaAaAaAaA n - aAaAaAaAaA
+(aA|bB)*+(aA|bB) aAaAbBaAaA n - aAaAbBaAaA
+(?:aA|bB)*+(?:aA|bB) aAaAaAbBaA n - aAaAaAbBaA
+(?:aA){1,5}+(?:aA) aAaAaAaAaA n - aAaAaAaAaA
+(aA){1,5}+(aA) aAaAaAaAaA n - aAaAaAaAaA
+(aA|bB){1,5}+(aA|bB) aAaAbBaAaA n - aAaAbBaAaA
+(?:aA|bB){1,5}+(?:aA|bB) bBbBbBbBbB n - bBbBbBbBbB
+(?:aA)?+(?:aA) aAb n - aAb
+(aA)?+(aA) aAb n - aAb
+(aA|bB)?+(aA|bB) bBb n - bBb
+(?:aA|bB)?+(?:aA|bB) aAb n - aAb
+(?:aA)++b aAaAaAaAaAb y $& aAaAaAaAaAb
+(aA)++b aAaAaAaAaAb y $& aAaAaAaAaAb
+(aA|bB)++b aAbBaAaAbBb y $& aAbBaAaAbBb
+(?:aA|bB)++b aAbBbBaAaAb y $& aAbBbBaAaAb
+(?:aA)*+b aAaAaAaAaAb y $& aAaAaAaAaAb
+(aA)*+b aAaAaAaAaAb y $& aAaAaAaAaAb
+(aA|bB)*+b bBbBbBbBbBb y $& bBbBbBbBbBb
+(?:aA|bB)*+b bBaAbBbBaAb y $& bBaAbBbBaAb
+(?:aA){1,5}+b aAaAaAaAaAb y $& aAaAaAaAaAb
+(aA){1,5}+b aAaAaAaAaAb y $& aAaAaAaAaAb
+(aA|bB){1,5}+b bBaAbBaAbBb y $& bBaAbBaAbBb
+(?:aA|bB){1,5}+b aAbBaAbBbBb y $& aAbBaAbBbBb
+(?:aA)?+b aAb y $& aAb
+(aA)?+b aAb y $& aAb
+(aA|bB)?+b bBb y $& bBb
+(?:aA|bB)?+b bBb y $& bBb
+foo(?:aA)++(?:aA) fooaAaAaAaAaA n - fooaAaAaAaAaA
+foo(aA)++(aA) fooaAaAaAaAaA n - fooaAaAaAaAaA
+foo(aA|bB)++(aA|bB) foobBbBbBaAaA n - foobBbBbBaAaA
+foo(?:aA|bB)++(?:aA|bB) fooaAaAaAaAaA n - fooaAaAaAaAaA
+foo(?:aA)*+(?:aA) fooaAaAaAaAaA n - fooaAaAaAaAaA
+foo(aA)*+(aA) fooaAaAaAaAaA n - fooaAaAaAaAaA
+foo(aA|bB)*+(aA|bB) foobBaAbBaAaA n - foobBaAbBaAaA
+foo(?:aA|bB)*+(?:aA|bB) fooaAaAbBbBaA n - fooaAaAbBbBaA
+foo(?:aA){1,5}+(?:aA) fooaAaAaAaAaA n - fooaAaAaAaAaA
+foo(aA){1,5}+(aA) fooaAaAaAaAaA n - fooaAaAaAaAaA
+foo(aA|bB){1,5}+(aA|bB) fooaAbBbBaAaA n - fooaAbBbBaAaA
+foo(?:aA|bB){1,5}+(?:aA|bB) fooaAbBbBaAbB n - fooaAbBbBaAbB
+foo(?:aA)?+(?:aA) fooaAb n - fooaAb
+foo(aA)?+(aA) fooaAb n - fooaAb
+foo(aA|bB)?+(aA|bB) foobBb n - foobBb
+foo(?:aA|bB)?+(?:aA|bB) fooaAb n - fooaAb
+foo(?:aA)++b fooaAaAaAaAaAb y $& fooaAaAaAaAaAb
+foo(aA)++b fooaAaAaAaAaAb y $& fooaAaAaAaAaAb
+foo(aA|bB)++b foobBaAbBaAbBb y $& foobBaAbBaAbBb
+foo(?:aA|bB)++b fooaAaAbBaAaAb y $& fooaAaAbBaAaAb
+foo(?:aA)*+b fooaAaAaAaAaAb y $& fooaAaAaAaAaAb
+foo(aA)*+b fooaAaAaAaAaAb y $& fooaAaAaAaAaAb
+foo(aA|bB)*+b foobBbBaAaAaAb y $& foobBbBaAaAaAb
+foo(?:aA|bB)*+b foobBaAaAbBaAb y $& foobBaAaAbBaAb
+foo(?:aA){1,5}+b fooaAaAaAaAaAb y $& fooaAaAaAaAaAb
+foo(aA){1,5}+b fooaAaAaAaAaAb y $& fooaAaAaAaAaAb
+foo(aA|bB){1,5}+b foobBaAaAaAaAb y $& foobBaAaAaAaAb
+foo(?:aA|bB){1,5}+b fooaAbBaAbBbBb y $& fooaAbBaAbBbBb
+foo(?:aA)?+b fooaAb y $& fooaAb
+foo(aA)?+b fooaAb y $& fooaAb
+foo(aA|bB)?+b foobBb y $& foobBb
+foo(?:aA|bB)?+b foobBb y $& foobBb
+
+([^()]++|\([^()]*\))+ ((abc(ade)ufh()()x y $& abc(ade)ufh()()x
+round\(([^()]++)\) _I(round(xs * sz),1) y $1 xs * sz
+
#
# \n in the tests are interpolated, as are variables of the form ${\w+}.
#
+# Blanks lines are treated as PASSING tests to keep the line numbers
+# linked to the test number.
+#
# If you want to add a regular expression test that can't be expressed
# in this format, don't add it here: put it in op/pat.t instead.
#
print "1..$numtests\n# $iters iterations\n";
TEST:
while (<TESTS>) {
+ if (!/\S/ || /^\s*#/) {
+ print "ok $. # (Blank line or comment)\n";
+ if (/\S/) { print $_ };
+ next;
+ }
chomp;
s/\\n/\n/g;
($pat, $subject, $result, $repl, $expect, $reason) = split(/\t/,$_,6);
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