Author: larry
Date: Mon Oct 9 15:35:46 2006
New Revision: 12964
Modified:
doc/trunk/design/syn/S05.pod
Log:
<!alpha> is not the same as <-alpha>, spotted by putter++
Made some of the whitespace rules more explicit.
Modified: doc/trunk/design/syn/S05.pod
==============================================================================
--- doc/trunk/design/syn/S05.pod (original)
+++ doc/trunk/design/syn/S05.pod Mon Oct 9 15:35:46 2006
@@ -16,7 +16,7 @@
Date: 24 Jun 2002
Last Modified: 9 Oct 2006
Number: 5
- Version: 37
+ Version: 38
This document summarizes Apocalypse 5, which is about the new regex
syntax. We now try to call them I<regex> rather than "regular
@@ -691,16 +691,18 @@
To pass a string with leading whitespace you must use the parenthesized form.
-If the first character is a plus or minus, the initial identifier is taken
-as a character class, so
+If the first character is a plus or minus, the initial identifier
+is taken as a character class, so the first character after the
+identifier doesn't matter in this case, and you can use whitespace
+however you like. Therefore
<foo+bar-baz>
-is equivalent to
+can be written
- <+foo+bar-baz>
+ <+ foo + bar - baz>
-(See below.)
+Likewise an initial left square bracket indicates character class syntax.
(See below.)
=item *
@@ -882,6 +884,10 @@
/ <[a..z_]>* /
/ <+[a..z_]>* /
+ / <+[ a..z _ ]>* /
+ / <+ [ a .. z _ ] >* /
+
+Whitespace is ignored within square brackets and after the initial C<+>.
=item *
@@ -893,12 +899,14 @@
/ <![a..z_]> . <!alpha> . /
+Whitespace is ignored after the initial C<->.
+
=item *
Character classes can be combined (additively or subtractively) within
-a single set of angle brackets. For example:
+a single set of angle brackets. Whitespace is ignored. For example:
- / <[a..z]-[aeiou]+xdigit> / # consonant or hex digit
+ / <[a..z] - [aeiou] + xdigit> / # consonant or hex digit
If such a combination starts with a named character class, a leading
C<+> is allowed but not required, provided the next character is a
@@ -906,6 +914,12 @@
/ <+alpha-[Jj]> / # J-less alpha
/ <alpha-[Jj]> / # same thing
+ / <+ alpha - [ Jj ]> / # still the same thing
+
+However, whitespace is not allowed after the first identifier if it
+immediately follows the left angle.
+
+ / <alpha - [Jj]> / # WRONG, means <alpha(/- [Jj]/)>
=item *
@@ -955,7 +969,9 @@
/ <!before _ > / # We aren't before an _
Note that C<< <!alpha> >> is different from C<< <-alpha> >> because the
-latter matches C</./> when it is not an alpha.
+latter matches C</./> when it is not an alpha. Note also that as a
+metacharacter C<!> doesn't change the parsing rules of whatever follows
+(unlike, say, C<+> or C<->).
=back
@@ -995,6 +1011,11 @@
these are dependent on the definition of C<< <ws> >>, but only on the C<\s>
definition of whitespace.)
+item *
+
+A C<< < >> followed by whitespace is illegal. Use C<< \< >> to match a literal
+left angle.
+
=back
=head1 Backslash reform
@@ -1004,7 +1025,7 @@
=item *
The C<\p> and C<\P> properties become intrinsic grammar rules such as
-(C<< <alpha> >> and C<< <!alpha> >>). They may be combined using the
+(C<< <alpha> >> and C<< <-alpha> >>). They may be combined using the
above-mentioned character class notation: C<< <[_]+alpha+digit> >>.
Regardless of the higher-level character class names, low-level
Unicode properties are always available with a prefix of C<is>.
