Question

1. I need to use std::regex and validate the input strings in C++
   Input strings should be between folder-1 or folder-01 or folder-001 to folder-200 (Prefix must be ‘folder-‘)
   How to write a regular expression for this?

2. Is the regular expressions uses in C++ different from regular expressions use in other languages such as PHP and JavaScript?

3. Do most C++ developers use ‘Boost regx’ or ‘std::regex’ (some comments please)?

Answer 1

Something like

const std::regex re("folder-\\d{1,3}");

example:

http://liveworkspace.org/code/1EfD0Q$12

You can read about std::regex in C++ standard, or about boost::regex in boost docs.
boost::regex is stable library and std::regex is new feature of C++11 standard.

Now, for example gcc 4.7 cannot handle this regex, so, use boost is better (in sample on LWS I use boost::regex instead of std::regex, since std::regex in gcc 4.7 cannot handle correctly {n, m}).