21 Strings library [strings]

21.4 String view classes [string.view]

21.4.2 Class template basic_­string_­view [string.view.template]

21.4.2.6 String operations [string.view.ops]

constexpr size_type copy(charT* s, size_type n, size_type pos = 0) const;
Let rlen be the smaller of n and size() - pos.
Throws: out_­of_­range if pos > size().
Expects: [s, s + rlen) is a valid range.
Effects: Equivalent to traits::copy(s, data() + pos, rlen).
Returns: rlen.
Complexity: .
constexpr basic_string_view substr(size_type pos = 0, size_type n = npos) const;
Let rlen be the smaller of n and size() - pos.
Throws: out_­of_­range if pos > size().
Effects: Determines rlen, the effective length of the string to reference.
Returns: basic_­string_­view(data() + pos, rlen).
constexpr int compare(basic_string_view str) const noexcept;
Let rlen be the smaller of size() and str.size().
Effects: Determines rlen, the effective length of the strings to compare.
The function then compares the two strings by calling traits::compare(data(), str.data(), rlen).
Complexity: .
Returns: The nonzero result if the result of the comparison is nonzero.
Otherwise, returns a value as indicated in Table 59.
Table 59compare() results
Condition
Return Value
size() < str.size()
< 0
size() == str.size()
 0
size() > str.size()
> 0
constexpr int compare(size_type pos1, size_type n1, basic_string_view str) const;
Effects: Equivalent to: return substr(pos1, n1).compare(str);
constexpr int compare(size_type pos1, size_type n1, basic_string_view str, size_type pos2, size_type n2) const;
Effects: Equivalent to: return substr(pos1, n1).compare(str.substr(pos2, n2));
constexpr int compare(const charT* s) const;
Effects: Equivalent to: return compare(basic_­string_­view(s));
constexpr int compare(size_type pos1, size_type n1, const charT* s) const;
Effects: Equivalent to: return substr(pos1, n1).compare(basic_­string_­view(s));
constexpr int compare(size_type pos1, size_type n1, const charT* s, size_type n2) const;
Effects: Equivalent to: return substr(pos1, n1).compare(basic_­string_­view(s, n2));
constexpr bool starts_with(basic_string_view x) const noexcept;
Effects: Equivalent to: return substr(0, x.size()) == x;
constexpr bool starts_with(charT x) const noexcept;
Effects: Equivalent to: return !empty() && traits::eq(front(), x);
constexpr bool starts_with(const charT* x) const;
Effects: Equivalent to: return starts_­with(basic_­string_­view(x));
constexpr bool ends_with(basic_string_view x) const noexcept;
Effects: Equivalent to:
return size() >= x.size() && compare(size() - x.size(), npos, x) == 0;
constexpr bool ends_with(charT x) const noexcept;
Effects: Equivalent to: return !empty() && traits::eq(back(), x);
constexpr bool ends_with(const charT* x) const;
Effects: Equivalent to: return ends_­with(basic_­string_­view(x));