[string.access] (original) (raw)

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]

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

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

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.

Complexity: Constant time.

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

Returns: operator[](pos).

Throws: out_of_rangeifpos >= size().

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

Hardened preconditions: empty() is false.

Effects: Equivalent to: return operator[](0);

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

Hardened preconditions: empty() is false.

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