c++ string iterator "find first of" - c++

Question

Is there a method in string iterator like find_first_of on string ?
Something like:
string::iterator it;
string str(" h asdasf ^& saafa");
it = FIND_FIRST_OF("&az^");
std::cout << *it << std::endl;
And the result:
a

Answer 1

You can do it indirectly
auto pos = str.find_first_of("&az^");
then advance the iterator
if(pos != std::string::npos) // thanks to #Mike Seymour
std::advance(it, pos);
I guess you can also do some kind of std::find with a lambda, but the above is really much more simpler and concise.

Answer 2

I think std::find_first_of is what you're looking for.
string::iterator it;
string str(" h asdasf ^& saafa");
string find_me ("&az^");
it = std::find_first_of (str.begin(), str.end(), find_me.begin(), find_me.end());
std::cout << *it << std::endl;
I would write a function to clean up the overhead involved in constructing/using the intermediary find_me variable if using this method with any frequency.

Answer 3

Try this:
std::string::size_type position = example.find_first_of(".");
if (position != std::string::npos)
{
std::advance(string_iterator, position);
}
else
{
string_iterator = example.end();
}

Answer 4

Class std::string has its own methods find_first_of and find_last_of apart from other find methods.
Here is a demonstrative program
#include <iostream>
#include <string>
int main()
{
std::string s( " h asdasf ^& saafa" );
auto pos = s.find_first_of( "&az^" );
if ( pos != std::string::npos ) std::cout << s[pos] << std::endl;
pos = s.find_last_of( "&az^" );
if ( pos != std::string::npos ) std::cout << s[pos] << std::endl;
return 0;
}
The program output is
a
a
Here is another demonstrative program that finds all characters in the string that are specified in the character literal
#include <iostream>
#include <string>
int main()
{
std::string s( " h asdasf ^& saafa" );
for ( std::string::size_type pos = 0;
( pos = s.find_first_of( "&az^", pos ) ) != std::string::npos;
++pos )
{
std::cout << pos << ": " << s[pos] << std::endl;
}
return 0;
}
The program output is
4: a
7: a
11: ^
12: &
15: a
16: a
18: a
Knowing the found position you always can get the corresponding iterator in the object:
std::string::iterator it = std::next( s.begin(), pos );
or
auto it = std::next( s.begin(), pos );
or simply
std::string::iterator it = s.begin() + pos;
Also there is standard algorithm std::find_first_of declared in header <algorithm> that also can be used with objects of type std::string.