21 Strings library [strings]

21.3 String classes [string.classes]

21.3.2 Class template basic_­string [basic.string]

21.3.2.7 String operations [string.ops]

21.3.2.7.1 Accessors [string.accessors]

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constexpr const charT* c_str() const noexcept; constexpr const charT* data() const noexcept;
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Returns: A pointer p such that p + i == addressof(operator[](i)) for each i in [0, size()].
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Complexity: Constant time.
3
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Remarks: The program shall not modify any of the values stored in the character array; otherwise, the behavior is undefined.
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constexpr charT* data() noexcept;
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Returns: A pointer p such that p + i == addressof(operator[](i)) for each i in [0, size()].
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Complexity: Constant time.
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Remarks: The program shall not modify the value stored at p + size() to any value other than charT(); otherwise, the behavior is undefined.
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constexpr operator basic_string_view<charT, traits>() const noexcept;
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Effects: Equivalent to: return basic_­string_­view<charT, traits>(data(), size());
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constexpr allocator_type get_allocator() const noexcept;
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Returns: A copy of the Allocator object used to construct the string or, if that allocator has been replaced, a copy of the most recent replacement.

21.3.2.7.2 Searching [string.find]

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Let F be one of find, rfind, find_­first_­of, find_­last_­of, find_­first_­not_­of, and find_­last_­not_­of.
  • (1.1)
    Each member function of the form 
    constexpr size_type F(const basic_string& str, size_type pos) const noexcept;
    has effects equivalent to: return F(basic_­string_­view<charT, traits>(str), pos);
  • (1.2)
    Each member function of the form 
    constexpr size_type F(const charT* s, size_type pos) const;
    has effects equivalent to: return F(basic_­string_­view<charT, traits>(s), pos);
  • (1.3)
    Each member function of the form 
    constexpr size_type F(const charT* s, size_type pos, size_type n) const;
    has effects equivalent to: return F(basic_­string_­view<charT, traits>(s, n), pos);
  • (1.4)
    Each member function of the form 
    constexpr size_type F(charT c, size_type pos) const noexcept;
    has effects equivalent to: 
    return F(basic_string_view<charT, traits>(addressof(c), 1), pos);
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template<class T> constexpr size_type find(const T& t, size_type pos = 0) const noexcept(see below); template<class T> constexpr size_type rfind(const T& t, size_type pos = npos) const noexcept(see below); template<class T> constexpr size_type find_first_of(const T& t, size_type pos = 0) const noexcept(see below); template<class T> constexpr size_type find_last_of(const T& t, size_type pos = npos) const noexcept(see below); template<class T> constexpr size_type find_first_not_of(const T& t, size_type pos = 0) const noexcept(see below); template<class T> constexpr size_type find_last_not_of(const T& t, size_type pos = npos) const noexcept(see below);
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Constraints:
  • (2.1)
    is_­convertible_­v<const T&, basic_­string_­view<charT, traits>> is true and
  • (2.2)
    is_­convertible_­v<const T&, const charT*> is false.
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Effects: Let G be the name of the function.
Equivalent to: 
basic_string_view<charT, traits> s = *this, sv = t;
return s.G(sv, pos);
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Remarks: The expression inside noexcept is equivalent to is_­nothrow_­convertible_­v<const T&, basic_­string_­view<charT, traits>>.

21.3.2.7.3 basic_­string​::​substr [string.substr]

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constexpr basic_string substr(size_type pos = 0, size_type n = npos) const;
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Throws: out_­of_­range if pos > size().
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Effects: Determines the effective length rlen of the string to copy as the smaller of n and size() - pos.
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Returns: basic_­string(data()+pos, rlen).

21.3.2.7.4 basic_­string​::​compare [string.compare]

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template<class T> constexpr int compare(const T& t) const noexcept(see below);
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Constraints:
  • (1.1)
    is_­convertible_­v<const T&, basic_­string_­view<charT, traits>> is true and
  • (1.2)
    is_­convertible_­v<const T&, const charT*> is false.
2
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Effects: Equivalent to: return basic_­string_­view<charT, traits>(*this).compare(t);
3
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Remarks: The expression inside noexcept is equivalent to is_­nothrow_­convertible_­v<const T&, basic_­string_­view<charT, traits>>.
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template<class T> constexpr int compare(size_type pos1, size_type n1, const T& t) const;
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Constraints:
  • (4.1)
    is_­convertible_­v<const T&, basic_­string_­view<charT, traits>> is true and
  • (4.2)
    is_­convertible_­v<const T&, const charT*> is false.
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Effects: Equivalent to: 
return basic_string_view<charT, traits>(*this).substr(pos1, n1).compare(t);
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template<class T> constexpr int compare(size_type pos1, size_type n1, const T& t, size_type pos2, size_type n2 = npos) const;
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Constraints:
  • (6.1)
    is_­convertible_­v<const T&, basic_­string_­view<charT, traits>> is true and
  • (6.2)
    is_­convertible_­v<const T&, const charT*> is false.
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Effects: Equivalent to: 
basic_string_view<charT, traits> s = *this, sv = t;
return s.substr(pos1, n1).compare(sv.substr(pos2, n2));
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constexpr int compare(const basic_string& str) const noexcept;
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Effects: Equivalent to: return compare(basic_­string_­view<charT, traits>(str));
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constexpr int compare(size_type pos1, size_type n1, const basic_string& str) const;
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Effects: Equivalent to: return compare(pos1, n1, basic_­string_­view<charT, traits>(str));
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constexpr int compare(size_type pos1, size_type n1, const basic_string& str, size_type pos2, size_type n2 = npos) const;
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Effects: Equivalent to: 
return compare(pos1, n1, basic_string_view<charT, traits>(str), pos2, n2);
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constexpr int compare(const charT* s) const;
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Effects: Equivalent to: return compare(basic_­string_­view<charT, traits>(s));
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constexpr int compare(size_type pos, size_type n1, const charT* s) const;
12
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Effects: Equivalent to: return compare(pos, n1, basic_­string_­view<charT, traits>(s));
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constexpr int compare(size_type pos, size_type n1, const charT* s, size_type n2) const;
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Effects: Equivalent to: return compare(pos, n1, basic_­string_­view<charT, traits>(s, n2));

21.3.2.7.5 basic_­string​::​starts_­with [string.starts.with]

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constexpr bool starts_with(basic_string_view<charT, traits> x) const noexcept; constexpr bool starts_with(charT x) const noexcept; constexpr bool starts_with(const charT* x) const;
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Effects: Equivalent to: 
return basic_string_view<charT, traits>(data(), size()).starts_with(x);

21.3.2.7.6 basic_­string​::​ends_­with [string.ends.with]

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constexpr bool ends_with(basic_string_view<charT, traits> x) const noexcept; constexpr bool ends_with(charT x) const noexcept; constexpr bool ends_with(const charT* x) const;
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Effects: Equivalent to: 
return basic_string_view<charT, traits>(data(), size()).ends_with(x);