24 Strings library [strings]

24.4 String view classes [string.view]

24.4.2 Class template basic_­string_­view [string.view.template]

24.4.2.7 Searching [string.view.find]

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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.

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

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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);

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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);

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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;

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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.

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Effects: Determines xpos.

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

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

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

  • (9.1)

    xpos <= pos

  • (9.2)

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

  • (9.3)

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

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Effects: Determines xpos.

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

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

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

  • (12.1)

    pos <= xpos

  • (12.2)

    xpos < size()

  • (12.3)

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

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Effects: Determines xpos.

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

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

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

  • (15.1)

    xpos <= pos

  • (15.2)

    xpos < size()

  • (15.3)

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

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Effects: Determines xpos.

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

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

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

  • (18.1)

    pos <= xpos

  • (18.2)

    xpos < size()

  • (18.3)

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

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Effects: Determines xpos.

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

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

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

  • (21.1)

    xpos <= pos

  • (21.2)

    xpos < size()

  • (21.3)

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

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Effects: Determines xpos.

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