Re: [Boost-users] [C++] Boost::Regex beginner question

Subject: Re: [Boost-users] [C++] Boost::Regex beginner question
From: Alan M. Carroll (amc_at_[hidden])
Date: 2008-12-18 18:59:01

Let's say you had an input form that was similar to that of Boost.Format
except that you could specify type information by appending a '|'
followed by the type, e.g. "%1|int%", and you could name the
inserts as well as use numbers (e.g., "%count|int%"). After
some preprocessing to pull out the types, you then wanted to strip the
type specifiers to make the string Boost.Format compliant. So
'%1|int%" would become "%1%" and "%2%" would
remain unchanged (because type specifiers are not required).

// This matches the insert strings, e.g. "%1|int%" with
subexpressions for the number or name
boost::regex
const

RXP_INSERT(
"%(?:(\\d+)|([_a-z][_a-z0-9]*))(?:[|]([_a-z][_:a-z0-9]*))?%"
, boost::regex_constants::icase);
// ...
// Time to strip the type specifiers. We match each insert then replace
with the first two groups,
// exactly one of which will be set ($1 if a number, $2 if name)
           
msgText = boost::regex_replace(msgText, RXP_INSERT,

"%$1$2%");
// No more type specifiers. Changing names to numbers is a bit more
complex but this should illustrate
// the principle.

At 04:41 PM 12/18/2008, P.C. wrote:

> my doubt is the following: I
> want to know how to do search and replace
> regexp operations, like it can be done in Perl by using groups
> (expressions
> surrounded by parentheses), which allow to select the substrings, matched
> by
> the regexp, in the form of $1, $2