cppdraft_translate/cppdraft/string/access.md

[string.access]

27 Strings library [strings]

27.4 String classes [string.classes]

27.4.3 Class template basic_string [basic.string]

27.4.3.6 Element access [string.access]

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constexpr const_reference operator[](size_type pos) const; constexpr reference operator[](size_type pos);

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Hardened preconditions: pos <= size() is true.

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Returns: *(begin() + pos) if pos < size().

Otherwise, returns a reference to an object of type charT with valuecharT(), where modifying the object to any value other thancharT() leads to undefined behavior.

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Throws: Nothing.

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Complexity: Constant time.

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constexpr const_reference at(size_type pos) const; constexpr reference at(size_type pos);

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Returns: operator.

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Throws: out_of_range ifpos >= size().

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constexpr const charT& front() const; constexpr charT& front();

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Hardened preconditions: empty() is false.

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Effects: Equivalent to: return operator;

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constexpr const charT& back() const; constexpr charT& back();

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Hardened preconditions: empty() is false.

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Effects: Equivalent to: return operator[](size() - 1);