MATLAB Programming

3 Basic Program Components
There are three types of explicit grouping operators that you can use when you
need to apply an operation to more than just one element in an expression.
Also in the grouping category is the alternative match (logical OR) operator, |.
This creates two or more groups of elements in the expression and applies an
operation to one of the groups.
Operator
(expr)
(?:expr)
(?>expr)
Usage
Group regular expressions and capture tokens.
Group regular expressions, but do not capture tokens.
Group atomically.
expr 1
|expr 2 Match expression expr 1
or expression expr 2
.
Grouping and Capture — (expr)
When you enclose an expression in parentheses, MATLAB not only treats all
oftheenclosedelementsasagroup,butalsocapturesatokenfromthese
elements whenever a match with the input string is found. For an example of
how to use this, see “Using Tokens — Example 1” on page 3-50.
Grouping Only — (?:expr)
Use (?:expr) to group a nonvowel (consonant, numeric, whitespace,
punctuation, etc.) followed by a vowel in the palindrome pstr. Specifyatleast
two consecutive occurrences ({2,}) of this group. Return the starting and
ending indices of the matched substrings:
pstr = 'Marge lets Norah see Sharon''s telegram';
expr = '(?:[^aeiou][aeiou]){2,}';
[mat ix1 ix2] = regexp(pstr, expr, 'match', 'start', 'end')
mat =
'Nora' 'haro' 'tele'
ix1 =
12 23 31
ix2 =
15 26 34
3-38