[Rcpp-devel] regular expression in Rcpp

On 1/13/2015 07:27, Mark Leeds wrote:

Hi All: I was trying to do something with regular expressions in Rcpp so
I piggy backed
heavily off of Dirk's boost.regex example in the Rcpp Gallery where he
takes streams of digits and checks them for machine and human readability.

Hi!

My problem is actually pretty different and simpler. Essentially, if a
character string ends in "rhofixed" or "norhofixed", then that part of the
character string should be removed. The R code below illiustrates what I'm
trying to do.

But, when I write the Rcpp code to do the same thing and  set
Sys.setenv("PKG_LIBS"="-lboost_regex"), I don't get the same result. I
don't know if  it's due to the regex engine being different in boost or I
could be doing something else wrong. Thanks for any help.

It does indeed seems simpler than an usual use case for regex. Hence,
perhaps you can go about it differently:
- use `boost::algorithm::ends_with` (from <boost/algorithm/string/predicate.hpp>)
to check whether your predicate (i.e., a character string ends in
"rhofixed" or "norhofixed") holds
- if so, use the `erase` member function (http://en.cppreference.com/w/
cpp/string/basic_string/substr) to get rid of the substring (note: if one
of the aforementioned predicates is satisfied, then you can trivially infer
how long is the substring subject to removal -- and can thus use, say, the
iterator-pair version, stepping backward from `std::end(your_string)` as
needed).

HTH!

Best,

Matt