C++ Primer Plus

size_type rfind(const charT* s, size_type pos = npos) const;

size_type rfind(const charT* s, size_type pos, size_type n) const;

size_type rfind(charT c, size_type pos = npos) const noexcept;

These methods work like the analogous find() methods, except that they find the last occurrence of a string or character that starts at or before position pos. If the substring is not found, the method returns npos.

Here’s code for finding the location of the substring "hat" in a longer string, starting at the end of the longer string:

string longer("That is a funny hat.");

string shorter("hat");

size_type loc1 = longer.rfind(shorter);           // sets loc1 to 16

size_type loc2 = longer.rfind(shorter, loc1 - 1); // sets loc2 to 1

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.

The find_last_of() Family

The find_last_of() methods have these prototypes:

size_type find_last_of (const basic_string& str,

                        size_type pos = npos) const noexcept;

size_type find_last_of (const charT* s, size_type pos, size_type n) const;

size_type find_last_of (const charT* s, size_type pos = npos) const;

size_type find_last_of (charT c, size_type pos = npos) const noexcept;

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

Here’s code for finding the location of the last and next to last occurrences of any of the letters in "fluke" in a longer string:

string longer("That is a funny hat.");

string shorter("hat");

size_type loc1 = longer.find_last_of(shorter);  // sets loc1 to 18

size_type loc2 = longer.find_last_of("any");    // sets loc2 to 17

The last occurrence of any of the three letters of hat in longer is the t in hat. The last occurrence of any of the three characters of any in longer is the a in hat.

The find_first_not_of() Family

The find_first_not_of() methods have these prototypes:

size_type find_first_not_of(const basic_string& str,

                           size_type pos = 0) const noexcept;

size_type find_first_not_of(const charT* s, size_type pos,

                            size_type n) const;

size_type find_first_not_of(const charT* s, size_type pos = 0) const;

size_type find_first_not_of(charT c, size_type pos = 0) const noexcept;

These methods work like the corresponding find_first_of() methods, except that they search for the first occurrence of any character not in the substring.

Here’s code for finding the location of the first two occurrences of any of the letters not in "This" in a longer string:

string longer("That is a funny hat.");

string shorter("This");

size_type loc1 = longer.find_first_not_of(shorter);  // sets loc1 to 2

size_type loc2 = longer.find_first_not_of("Thatch"); // sets loc2 to 4

The a in That is the first character in longer that does not appear in This. The first space in the longer string is the first character not present in Thatch.

The find_last_not_of() Family

The find_last_not_of() methods have these prototypes:

size_type find_last_not_of (const basic_string& str,

                            size_type pos = npos) const noexcept;

size_type find_last_not_of (const charT* s, size_type pos,

                            size_type n) const;

size_type find_last_not_of (const charT* s,

                            size_type pos = npos) const;

size_type find_last_not_of (charT c, size_type pos = npos) const noexcept;

These methods work like the corresponding find_last_of() methods, except that they search for the last occurrence of any character not in the substring.

Here’s code for finding the location of the last two occurrences of any of the letters not in "This" in a longer string:

string longer("That is a funny hat.");

string shorter("That.");

size_type loc1 = longer.find_last_not_of(shorter);     // sets loc1 to 15

size_type loc2 = longer.find_last_not_of(shorter, 10); // sets loc2 to 10

The last space in longer is the last character in longer that does not appear in shorter. The f in the longer string is the last character not present in shorter found up through position 10.

Comparison Methods and Functions