MATLAB Programming Fundamentals - MathWorks

ans =

'g11n'

Using a dynamic expression ${num2str(length($2))} enables you to base the

replacement expression on the input text so that you do not have to change the

expression each time. This example uses the dynamic replacement syntax ${cmd}.

match_expr = '(^\w)(\w*)(\w$)';

replace_expr = '$1${num2str(length($2))}$3';

regexprep('internationalization', match_expr, replace_expr)

ans =

'i18n'

regexprep('globalization', match_expr, replace_expr)

ans =

'g11n'

When parsed, a dynamic expression must correspond to a complete, valid regular

expression. In addition, dynamic match expressions that use the backslash escape

character (\) require two backslashes: one for the initial parsing of the expression, and

one for the complete match. The parentheses that enclose dynamic expressions do not

create a capturing group.

There are three forms of dynamic expressions that you can use in match expressions, and

one form for replacement expressions, as described in the following sections

Dynamic Match Expressions — (??expr)

The (??expr) operator parses expression expr, and inserts the results back into the

match expression. MATLAB then evaluates the modified match expression.

Here is an example of the type of expression that you can use with this operator:

chr = {'5XXXXX', '8XXXXXXXX', '1X'};

regexp(chr, '^(\d+)(??X{$1})$', 'match', 'once');

The purpose of this particular command is to locate a series of X characters in each of the

character vectors stored in the input cell array. Note however that the number of Xs

2 Program Components