23 Strings library [strings]

23.3 String view classes [string.view]

23.3.3 Class template basic_string_view [string.view.template]

23.3.3.9 Searching [string.view.find]

Member functions in this subclause have complexity at worst, although implementations should do better.
Let F be one of find, rfind, find_first_of, find_last_of, find_first_not_of, and find_last_not_of.
  • Each member function of the form constexpr return-type F(const charT* s, size_type pos) const; has effects equivalent to: return F(basic_string_view(s), pos);
  • Each member function of the form constexpr return-type F(const charT* s, size_type pos, size_type n) const; has effects equivalent to: return F(basic_string_view(s, n), pos);
  • Each member function of the form constexpr return-type F(charT c, size_type pos) const noexcept; has effects equivalent to: return F(basic_string_view(addressof(c), 1), pos);
constexpr size_type find(basic_string_view str, size_type pos = 0) const noexcept;
Let xpos be the lowest position, if possible, such that the following conditions hold:
  • pos <= xpos
  • xpos + str.size() <= size()
  • traits​::​eq(at(xpos + I), str.at(I)) for all elements I of the string referenced by str.
Effects: Determines xpos.
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;
Let xpos be the highest position, if possible, such that the following conditions hold:
  • xpos <= pos
  • xpos + str.size() <= size()
  • traits​::​eq(at(xpos + I), str.at(I)) for all elements I of the string referenced by str.
Effects: Determines xpos.
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;
Let xpos be the lowest position, if possible, such that the following conditions hold:
  • pos <= xpos
  • xpos < size()
  • traits​::​eq(at(xpos), str.at(I)) for some element I of the string referenced by str.
Effects: Determines xpos.
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;
Let xpos be the highest position, if possible, such that the following conditions hold:
  • xpos <= pos
  • xpos < size()
  • traits​::​eq(at(xpos), str.at(I)) for some element I of the string referenced by str.
Effects: Determines xpos.
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;
Let xpos be the lowest position, if possible, such that the following conditions hold:
  • pos <= xpos
  • xpos < size()
  • traits​::​eq(at(xpos), str.at(I)) for no element I of the string referenced by str.
Effects: Determines xpos.
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;
Let xpos be the highest position, if possible, such that the following conditions hold:
  • xpos <= pos
  • xpos < size()
  • traits​::​eq(at(xpos), str.at(I)) for no element I of the string referenced by str.
Effects: Determines xpos.
Returns: xpos if the function can determine such a value for xpos.
Otherwise, returns npos.