manpagez: man pages & more
info bigloo
Home | html | info | man
[ << ] [ < ] [ Up ] [ > ] [ >> ]         [Top] [Contents] [Index] [ ? ]

13.2.1 Basic assertions

The assertions ^ and $ identify the beginning and the end of the text string respectively. They ensure that their adjoining regexps match at one or other end of the text string. Examples:

(pregexp-match-positions "^contact" "first contact") ⇒ #f 

The regexp fails to match because contact does not occur at the beginning of the text string.

(pregexp-match-positions "laugh$" "laugh laugh laugh laugh") ⇒ ((18 . 23))

The regexp matches the last laugh.

The metasequence \b asserts that a word boundary exists.

(pregexp-match-positions "yack\\b" "yackety yack") ⇒ ((8 . 12))

The yack in yackety doesn’t end at a word boundary so it isn’t matched. The second yack does and is.

The metasequence \B has the opposite effect to \b. It asserts that a word boundary does not exist.

(pregexp-match-positions "an\\B" "an analysis") ⇒ ((3 . 5))

The an that doesn’t end in a word boundary is matched.


This document was generated on October 23, 2011 using texi2html 5.0.