The find_first_of() Family

The find_first_of() methods have these prototypes:

size_type find_first_of(const basic_string& str,
                        size_type pos = 0) const noexcept;
size_type find_first_of(const charT* s, size_type pos, size_type n) const;
size_type find_first_of(const charT* s, size_type pos = 0) const;
size_type find_first_of(charT c, size_type pos = 0) const noexcept;

These methods work like the corresponding find() methods, except that instead of looking for a match of the entire substring, they look for the first match for any single character in the substring:

string longer("That is a funny hat.");
string shorter("fluke");
size_type loc1 = longer.find_first_of(shorter);  // sets loc1 to 10
size_type loc2 = longer.find_first_of("fat");    // sets loc2 to 2

The first occurrence of any of the five characters of fluke in longer is the f in funny. The first occurrence of any of three characters of fat in longer is the a in That.