Question

The standard library provides std::advance, but that only advances an iterator to a given offset.

Writing that algorithm yourself is pretty trivial:

template<class Iter, class T>
void advance_until(Iter& it, Iter end, T const& delim){
  while(it != end && *it != delim)
    ++it;
}

Or even:

template<class Iter, class T>
void unsafe_advance_until(Iter& it, T const& delim){
  while(*it != delim)
    ++it;
}

Which would more closely model the way std::advance behaves.

Usage example:

std::string s("hello world!");
std::string::iterator it(s.begin());
advance_until(it, s.end(), 'w');
//unsafe_advance_until(it, 'w');
if(it != s.end())
  std::cout << *it << '\n'; // prints 'w'

But maybe there’s already something like that in the standard library or Boost, so I thought I’d ask away.

Answer 1

This is commonly known as std::find():

std::string::iterator it = std::find(s.begin(), s.end(), 'w');

if (it == s.end()) { /* not found */ }
else               { /* found *it */ }

Successive items can be found through a loop:

while (it != s.end())
{
  // ...
  ++it; // always valid
  it = std::find(it, s.end(), 'w');
}