How to use in C++11

Question

I'm trying to use a regular expression to accept strings that have sequences like

ifelseifelseififif

So every else needs an if, but not every if needs an else. I know I could do this with pen and paper with a simple regular expression like this ((if)*+(ifelse)*)* .Now I'm not sure if I'll be able to do this with the library as I've never used it before. So would it be possible to accept or reject a string based on a regular expression like the one I wrote above?

I wrote this sample to get my feet wet and I don't understand why it returns false. Isn't regex_search() supposed to find substring matches? That snippet prints nope every time.

#include <regex>
#include <iostream>
using namespace std;

int main(){
  string sequence="ifelse";
  regex rx("if");
  if(regex_search(sequence.begin(),sequence.end(),rx)){
    cout<<"match found"<<endl;
  }else{
    cout<<"nope"<<endl;
  }
}

I'm using g++ 4.7 and have tried compiling with both g++ -std=gnu+11 reg.cpp and g++ -std=c++11 reg.cpp

not yet fully supported, considering . it worked, see this [post](http://stackoverflow.com/questions/8060025/is-this-c11-regex-error-me-or-the-compiler). — gongzhitaao, May 03 '13 at 01:37
possible duplicate of [No matches with c++11 regex](http://stackoverflow.com/questions/11269766/no-matches-with-c11-regex) — nhahtdh, May 03 '13 at 04:45
@gongzhitaao - "not yet fully supported" doesn't do it justice. There's nothing useful there, and the useless `` header should not have been put into gcc's library implementation. — Pete Becker, May 03 '13 at 11:50

score 1 · Accepted Answer · answered May 03 '13 at 01:32

1

If you are compiling with g++ it may be because regex is not fully supported yet. See here for current C++11 status in g++.

answered May 03 '13 at 01:32

Dr.Tower

985
5
11

I added my compiler flag sup above, I guess I'm going to try to switch to visual studio instead of emacs with g++ – Tyler Pfaff May 03 '13 at 01:46
1

@TylerPfaff No need to get drastic. You could just use boost/regex or one of the other available regex implementations out there. – Cubic May 03 '13 at 08:11

score 1 · Answer 2 · answered May 03 '13 at 01:34

1

This prints "match found", I just ran it. It wouldn't compile if you weren't using c++11 but heres how I compiled it. clang++ -std=c++11 -stdlib=libc++ reg.cpp

answered May 03 '13 at 01:34

aaronman

18,343
7
63
78

I added my compiler flag sup above, I guess I'm going to try to switch to visual studio instead of emacs with g++ – Tyler Pfaff May 03 '13 at 01:37
generally you will need to use the flag -stdlib=libc++ – aaronman May 03 '13 at 01:48
@aaronman libc++ is atm pretty much only an option on OSX when using clang. – Cubic May 03 '13 at 08:12
How would you make use of c++11 libs on linux or windows than. – aaronman May 03 '13 at 16:10

How to use in C++11

2 Answers2