MATLAB Programming

Regular Expressions
This section covers
• “Operators Used with Tokens” on page 3-49
• “Introduction to Using Tokens” on page 3-49
• “Using Tokens — Example 1” on page 3-50
• “Using Tokens — Example 2” on page 3-51
• “TokensThatAreNotMatched”onpage3-52
• “Using Tokens in a Replacement String” on page 3-53
Operators Used with Tokens
Here are the operators you can use with tokens in MATLAB.
Operator
(expr)
Usage
Capture in a token all characters matched by the
expression within the parentheses.
\N Match the N th token generated by this command. That is,
use \1 to match the first token, \2 to match the second,
and so on.
$N Insert the match for the N th tokeninthereplacement
string. Used only by the regexprep function. If N
is equal to zero, then insert the entire match in the
replacement string.
(?(N)s1|s2)
If N th token is found, then match s1, elsematchs2
Introduction to Using Tokens
You can turn any pattern being matched into a token by enclosing the
pattern in parentheses within the expression. For example, to create a token
for a dollar amount, you could use ’(\$\d+)’. Each token in the expression
is assigned a number, starting from 1, going from left to right. To make a
reference to a token later in the expression, refer to it using a backslash
followed by the token number. For example, when referencing a token
generated by the third set of parentheses in the expression, use \3.
3-49