Binary search with returned index in STL?

Question

I need a binary search function.

I couldn\'t find any function in the standard library that will return the index of the found item, and if it wasn\'t found,

Answer 1

using STL we can find the index

vector vec{1,2,3,4,5,6,7,8,9} ;
vector :: iterator index;
index=lower_bound(vec.begin(),vec.end(),search_data);
return (index-vec.begin());