21 Strings library [strings]

21.4 String view classes [string.view]

21.4.2 Class template basic_string_view [string.view.template]

21.4.2.7 Searching [string.view.find]

1

This section specifies the basic_string_view member functions named find, rfind, find_first_of, find_last_of, find_first_not_of, and find_last_not_of.

2

Member functions in this section have complexity Ο(size() * str.size()) at worst, although implementations are encouraged to do better.

3

Each member function of the form 

constexpr return-type F(const charT* s, size_type pos);

is equivalent to return F(basic_string_view(s), pos);

4

Each member function of the form 

constexpr return-type F(const charT* s, size_type pos, size_type n);

is equivalent to return F(basic_string_view(s, n), pos);

5

Each member function of the form 

constexpr return-type F(charT c, size_type pos);

is equivalent to return F(basic_string_view(&c, 1), pos);

constexpr size_type find(basic_string_view str, size_type pos = 0) const noexcept;

6

Let xpos be the lowest position, if possible, such that the following conditions hold:

  • (6.1)

    pos <= xpos

  • (6.2)

    xpos + str.size() <= size()

  • (6.3)

    traits::eq(at(xpos + I), str.at(I)) for all elements I of the string referenced by str.

7

Effects: Determines xpos.

8

Returns: xpos if the function can determine such a value for xpos. Otherwise, returns npos.

9

Remarks: Uses traits::eq().

constexpr size_type rfind(basic_string_view str, size_type pos = npos) const noexcept;

10

Let xpos be the highest position, if possible, such that the following conditions hold:

  • (10.1)

    xpos <= pos

  • (10.2)

    xpos + str.size() <= size()

  • (10.3)

    traits::eq(at(xpos + I), str.at(I)) for all elements I of the string referenced by str.

11

Effects: Determines xpos.

12

Returns: xpos if the function can determine such a value for xpos. Otherwise, returns npos.

13

Remarks: Uses traits::eq().

constexpr size_type find_first_of(basic_string_view str, size_type pos = 0) const noexcept;

14

Let xpos be the lowest position, if possible, such that the following conditions hold:

  • (14.1)

    pos <= xpos

  • (14.2)

    xpos < size()

  • (14.3)

    traits::eq(at(xpos), str.at(I)) for some element I of the string referenced by str.

15

Effects: Determines xpos.

16

Returns: xpos if the function can determine such a value for xpos. Otherwise, returns npos.

17

Remarks: Uses traits::eq().

constexpr size_type find_last_of(basic_string_view str, size_type pos = npos) const noexcept;

18

Let xpos be the highest position, if possible, such that the following conditions hold:

  • (18.1)

    xpos <= pos

  • (18.2)

    xpos < size()

  • (18.3)

    traits::eq(at(xpos), str.at(I)) for some element I of the string referenced by str.

19

Effects: Determines xpos.

20

Returns: xpos if the function can determine such a value for xpos. Otherwise, returns npos.

21

Remarks: Uses traits::eq().

constexpr size_type find_first_not_of(basic_string_view str, size_type pos = 0) const noexcept;

22

Let xpos be the lowest position, if possible, such that the following conditions hold:

  • (22.1)

    pos <= xpos

  • (22.2)

    xpos < size()

  • (22.3)

    traits::eq(at(xpos), str.at(I)) for no element I of the string referenced by str.

23

Effects: Determines xpos.

24

Returns: xpos if the function can determine such a value for xpos. Otherwise, returns npos.

25

Remarks: Uses traits::eq().

constexpr size_type find_last_not_of(basic_string_view str, size_type pos = npos) const noexcept;

26

Let xpos the highest position, if possible, such that the following conditions hold:

  • (26.1)

    xpos <= pos

  • (26.2)

    xpos < size()

  • (26.3)

    traits::eq(at(xpos), str.at(I)) for no element I of the string referenced by str.

27

Effects: Determines xpos.

28

Returns: xpos if the function can determine such a value for xpos. Otherwise, returns npos.

29

Remarks: Uses traits::eq().