7.4 Built-in Rules

     

A number of named rules are provided by default, including a complete set of POSIX-style classes, and Unicode property classes. The list isn't fully defined yet, but Table 7-7 shows a few you're likely to see.

Table 7-7. Built-in rules

Rule

Meaning

<alpha>

Match a Unicode alphabetic character.

<digit>

Match a Unicode digit.

<sp>

Match a single-space character (the same as \s ).

<ws>

Match any whitespace (the same as \s+ ).

<null>

Match the null string.

<prior>

Match the same thing as the previous match.

<before . . . >

Zero-width lookahead . Assert that you're before a pattern.

<after . . . >

Zero-width lookbehind. Assert that you're after a pattern.

<prop . . . >

Match any character with the named property.

<replace( . . . )>

Replace everything matched so far in the rule or subrule with the given string (under consideration).


The <null> rule matches a zero-width string (so it's always true) and <prior> matches whatever the most recent successful rule matched. These replace the two behaviors of the Perl 5 null pattern // , which is no longer valid syntax for rules.



Perl 6 and Parrot Essentials
Perl 6 and Parrot Essentials, Second Edition
ISBN: 059600737X
EAN: 2147483647
Year: 2003
Pages: 116

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