`lookAheadBoundary`

Pattern that requires a given pattern to follow, without consuming it.

Category: Language Fundamentals > Data Types

Syntax

pat = lookAheadBoundary(p)

Matches a position that is followed by text matching p.

Description

A look-ahead lets a pattern depend on its context. 'cat' + lookAheadBoundary('fish') matches cat only when fish comes right after it, and returns just cat. The related lookBehindBoundary checks what comes before instead.

Input arguments

p: Pattern or text that must come next.

Output arguments

pat: A pattern object of zero width: the text matched by p is checked but not included in the result.

Example

Match only before a context

s = 'catfish dogcat';
extract(s, 'cat' + lookAheadBoundary('fish'))

Output

ans = "cat"

See also

lookBehindBoundary pattern extract contains regexp