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Re: [ID 20010626.005] regex (?<name>...) capture-to-var paren, new $^N magic variable
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From:
Jeffrey Friedl
Date:
June 30, 2001 00:55
Subject:
Re: [ID 20010626.005] regex (?<name>...) capture-to-var paren, new $^N magic variable
Message ID:
200106300755.AAA09023@ventrue.corp.yahoo.com
Here are the docs and tests.
Jeffrey
diff -ru pod/.orig/perlretut.pod pod/perlretut.pod
--- pod/.orig/perlretut.pod Tue Jun 12 18:39:57 2001
+++ pod/perlretut.pod Fri Jun 29 23:51:13 2001
@@ -710,9 +710,12 @@
/(ab(cd|ef)((gi)|j))/;
1 2 34
-so that if the regexp matched, e.g., C<$2> would contain 'cd' or 'ef'.
-For convenience, perl sets C<$+> to the highest numbered C<$1>, C<$2>,
-... that got assigned.
+so that if the regexp matched, e.g., C<$2> would contain 'cd' or 'ef'. For
+convenience, perl sets C<$+> to the string held by the highest numbered
+C<$1>, C<$2>, ... that got assigned (and, somewhat related, C<$^N> to the
+value of the C<$1>, C<$2>, ... most-recently assigned; i.e. the C<$1>,
+C<$2>, ... associated with the rightmost closing parenthesis used in the
+match).
Closely associated with the matching variables C<$1>, C<$2>, ... are
the B<backreferences> C<\1>, C<\2>, ... . Backreferences are simply
diff -ru pod/.orig/perltoc.pod pod/perltoc.pod
--- pod/.orig/perltoc.pod Tue Jun 26 08:00:08 2001
+++ pod/perltoc.pod Fri Jun 29 23:45:32 2001
@@ -904,7 +904,7 @@
$EVAL_ERROR, $@, $PROCESS_ID, $PID, $$, $REAL_USER_ID, $UID, $<,
$EFFECTIVE_USER_ID, $EUID, $>, $REAL_GROUP_ID, $GID, $(,
$EFFECTIVE_GROUP_ID, $EGID, $), $PROGRAM_NAME, $0, $[, $], $COMPILING, $^C,
-$DEBUGGING, $^D, $SYSTEM_FD_MAX, $^F, $^H, %^H, $INPLACE_EDIT, $^I, $^M,
+$DEBUGGING, $^D, $SYSTEM_FD_MAX, $^F, $^H, %^H, $INPLACE_EDIT, $^I, $^M, $^N,
$OSNAME, $^O, $PERLDB, $^P, 0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80,
0x100, 0x200, $LAST_REGEXP_CODE_RESULT, $^R, $EXCEPTIONS_BEING_CAUGHT, $^S,
$BASETIME, $^T, $PERL_VERSION, $^V, $WARNING, $^W, ${^WARNING_BITS},
diff -ru pod/.orig/perlvar.pod pod/perlvar.pod
--- pod/.orig/perlvar.pod Mon Jun 18 07:42:24 2001
+++ pod/perlvar.pod Sat Jun 30 00:04:05 2001
@@ -180,14 +180,29 @@
=item $+
-The last bracket matched by the last search pattern. This is useful if
-you don't know which one of a set of alternative patterns matched. For
-example:
+The text matched by the last bracket of the last successful search pattern.
+This is useful if you don't know which one of a set of alternative patterns
+matched. For example:
/Version: (.*)|Revision: (.*)/ && ($rev = $+);
(Mnemonic: be positive and forward looking.)
This variable is read-only and dynamically scoped to the current BLOCK.
+
+=item $^N
+
+The text matched by the used group most-recently closed (i.e. the group
+with the rightmost closing parenthesis) of the last successful search
+pattern. This is primarly used inside C<(?{...})> blocks for examining text
+recently matched. For example, to effectively capture text to a variable
+(in addition to C<$1>, C<$2>, etc.), replace C<(...)> with
+
+ (?:(...)(?{ $var = $^N }))
+
+By setting and then using C<$var> in this way relieves you from having to
+worry about exactly which numbered set of parentheses they are.
+
+This variable is dynamically scoped to the current BLOCK.
=item @LAST_MATCH_END
--- t/op/.orig/pat.t Thu Jun 28 20:17:51 2001
+++ t/op/pat.t Sat Jun 30 00:52:21 2001
@@ -6,7 +6,7 @@
$| = 1;
-print "1..639\n";
+print "1..660\n";
BEGIN {
chdir 't' if -d 't';
@@ -1854,3 +1854,38 @@
print "not " unless " " =~ /[[:print:]]/;
print "ok 639\n";
+##
+## Test basic $^N usage outside of a regex
+##
+$x = "abcdef";
+$T="ok 640\n";if ($x =~ /cde/ and not defined $^N) {print $T} else {print "not $T"};
+$T="ok 641\n";if ($x =~ /(cde)/ and $^N eq "cde") {print $T} else {print "not $T"};
+$T="ok 642\n";if ($x =~ /(c)(d)(e)/ and $^N eq "e") {print $T} else {print "not $T"};
+$T="ok 643\n";if ($x =~ /(c(d)e)/ and $^N eq "cde") {print $T} else {print "not $T"};
+$T="ok 644\n";if ($x =~ /(foo)|(c(d)e)/ and $^N eq "cde") {print $T} else {print "not $T"};
+$T="ok 645\n";if ($x =~ /(c(d)e)|(foo)/ and $^N eq "cde") {print $T} else {print "not $T"};
+$T="ok 646\n";if ($x =~ /(c(d)e)|(abc)/ and $^N eq "abc") {print $T} else {print "not $T"};
+$T="ok 647\n";if ($x =~ /(c(d)e)|(abc)x/ and $^N eq "cde") {print $T} else {print "not $T"};
+$T="ok 648\n";if ($x =~ /(c(d)e)(abc)?/ and $^N eq "cde") {print $T} else {print "not $T"};
+$T="ok 649\n";if ($x =~ /(?:c(d)e)/ and $^N eq "d" ) {print $T} else {print "not $T"};
+$T="ok 650\n";if ($x =~ /(?:c(d)e)(?:f)/ and $^N eq "d" ) {print $T} else {print "not $T"};
+$T="ok 651\n";if ($x =~ /(?:([abc])|([def]))*/ and $^N eq "f" ){print $T} else {print "not $T"};
+$T="ok 652\n";if ($x =~ /(?:([ace])|([bdf]))*/ and $^N eq "f" ){print $T} else {print "not $T"};
+$T="ok 653\n";if ($x =~ /(([ace])|([bd]))*/ and $^N eq "e" ){print $T} else {print "not $T"};
+{
+ $T="ok 654\n";if($x =~ /(([ace])|([bdf]))*/ and $^N eq "f" ){print $T} else {print "not $T"};
+}
+## test to see if $^N is automatically localized -- it should now
+## have the value set in test 653
+$T="ok 655\n";if ($^N eq "e" ){print $T} else {print "not $T"};
+
+##
+## Now test inside (?{...})
+##
+$T="ok 656\n";if ($x =~ /a([abc])(?{$y=$^N})c/ and $y eq "b" ){print $T} else {print "not $T"};
+$T="ok 657\n";if ($x =~ /a([abc]+)(?{$y=$^N})d/ and $y eq "bc"){print $T} else {print "not $T"};
+$T="ok 658\n";if ($x =~ /a([abcdefg]+)(?{$y=$^N})d/ and $y eq "bc"){print $T} else {print "not $T"};
+$T="ok 659\n";if ($x =~ /(a([abcdefg]+)(?{$y=$^N})d)(?{$z=$^N})e/ and $y eq "bc" and $z eq "abcd")
+ {print $T} else {print "not $T"};
+$T="ok 660\n";if ($x =~ /(a([abcdefg]+)(?{$y=$^N})de)(?{$z=$^N})/ and $y eq "bc" and $z eq "abcde")
+ {print $T} else {print "not $T"};
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