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3.12.1 Regular expression syntax

.

Matches any single character except a newline. For example, c.r matches any three character string starting with c and ending with r .

*

Matches the previous regexp any number of times (including zero times). For example, ca*r matches strings beginning with c and ending with r , with any number of a s in-between.

+

Matches the previous regexp any number of times, but at least once. For example, ca+r matches strings beginning with c and ending with r , with at least one a in-between.

?

Matches the previous regexp either 0 or 1 times. For example, ca?r matches either the string cr or car , and nothing else.

^

Matches the next regexp as long as it is at the beginning of a line. For example, ^foo matches the string foo as long as it is at the beginning of a line.

$

Matches the previous regexp as long as it is at the end of a line. For example, foo$ matches the string foo as long as it is at the end of a line.

[ ]

Contains a character set to be used for matching, where the other special characters mentioned do not apply. The empty string is automatically part of the character set. For example, [a.b] matches either a or . or b or the empty string. The regexp c[ad]*r matches strings beginning with c and ending with r , with any number of a s and d s in-between.

The characters - and ^ have special meanings inside character sets. - defines a range and ^ defines a complement character set. For example, [a-d] matches any character in the range a to d inclusive, and [^ab] matches any character except a or b .

\

Quotes the special characters. For example, \* matches the character * (that is, * has lost its special meaning).

\|

Specifies an alternative. For example, ab\|cd matches either ab or cd .

\( , \)

Provides a grouping construct. For example, ab\(cd\|ef\) matches either abcd or abef .


Common LispWorks User Guide (Macintosh version) - 21 Feb 2008

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