boost::split leaves empty tokens at the beginning and end of string - is this desired behaviour?
boost, c++, c++11, split
Solution
The behavior is intentional, because you could recreate the string (complete with starting and trailing spaces) from the split version. Boost doesn't know if that whitespace is significant or not to you (it might be, as some file formats, for example, might force leading spaces/specific space counts).
You should `trim_if` or `trim` as you are if you do need to remove leading/trailing spaces.
Problem
Since I couldn't find anything on this in the documentation, I thought I ask it here. I have the following program (C++11): ``` #include <iostream> #include <boost/algorithm/string.hpp> using namespace std; using namespace boost; int main () { string tmp = " #tag #tag1#tag2 #tag3 ####tag4 "; list<iterator_range<string::iterator> > matches; split( matches, tmp, is_any_of("\t #"), token_compress_on ); for( auto match: matches ) { cout << "'" << match << "'\n"; } } ``` The output is: ``` '' 'tag' 'tag1' 'tag2' 'tag3' 'tag4' '' ``` I would have thought that the `token_compress_on` option removes all empty tokens. The solution is, for example, to use `boost::trim_if`. Nevertheless I was wondering if this is the desired behaviour of boost::split, and why this is happening? (g++ 4.6.3, boost 1.48)