MATLAB Programming Fundamentals - MathWorks

Grouping

Operator

Description Example

(expr) Group elements of the expression and

capture tokens.

'Joh?n\s(\w*)' captures a token that

contains the last name of any person

with the first name John or Jon.

(?:expr) Group, but do not capture tokens. '(?:[aeiou][^aeiou]){2}' matches

two consecutive patterns of a vowel

followed by a nonvowel, such as 'anon'.

Without grouping, '[aeiou][^aeiou]

{2}'matches a vowel followed by two

nonvowels.

(?>expr) Group atomically. Do not backtrack

within the group to complete the match,

and do not capture tokens.

'A(?>.*)Z' does not match 'AtoZ',

although 'A(?:.*)Z' does. Using the

atomic group, Z is captured using .* and

is not rescanned.

(expr1|

expr2)

Match expression expr1 or expression

expr2.

If there is a match with expr1, then

expr2 is ignored.

You can include ?: or ?> after the

opening parenthesis to suppress tokens

or group atomically.

'(let|tel)\w+' matches words that

start with let or tel.

Anchors

Anchors in the expression match the beginning or end of a character vector or word.

Anchor Matches the... Example

^expr Beginning of the input text. '^M\w*' matches a word starting with M

at the beginning of the text.

expr$ End of the input text. '\w*m$' matches words ending with m

at the end of the text.

\<expr Beginning of a word. '\<n\w*' matches any words starting

with n.

2 Program Components