30 Localization library [localization]

30.3 Locales [locales]

30.3.1 Class locale [locale]

30.3.1.3 Constructors and destructor [locale.cons]

locale() noexcept;
Effects: Constructs a copy of the argument last passed to locale​::​global(locale&), if it has been called; else, the resulting facets have virtual function semantics identical to those of locale​::​classic().
[Note 1: 
This constructor yields a copy of the current global locale.
It is commonly used as a default argument for function parameters of type const locale&.
— end note]
explicit locale(const char* std_name);
Effects: Constructs a locale using standard C locale names, e.g., "POSIX".
The resulting locale implements semantics defined to be associated with that name.
Throws: runtime_error if the argument is not valid, or is null.
Remarks: The set of valid string argument values is "C", "", and any implementation-defined values.
explicit locale(const string& std_name);
Effects: Equivalent to locale(std_name.c_str()).
locale(const locale& other, const char* std_name, category cats);
Preconditions: cats is a valid category value ([locale.category]).
Effects: Constructs a locale as a copy of other except for the facets identified by the category argument, which instead implement the same semantics as locale(std_name).
Throws: runtime_error if the second argument is not valid, or is null.
Remarks: The locale has a name if and only if other has a name.
locale(const locale& other, const string& std_name, category cats);
Effects: Equivalent to locale(other, std_name.c_str(), cats).
template<class Facet> locale(const locale& other, Facet* f);
Effects: Constructs a locale incorporating all facets from the first argument except that of type Facet, and installs the second argument as the remaining facet.
If f is null, the resulting object is a copy of other.
Remarks: If f is null, the resulting locale has the same name as other.
Otherwise, the resulting locale has no name.
locale(const locale& other, const locale& one, category cats);
Preconditions: cats is a valid category value.
Effects: Constructs a locale incorporating all facets from the first argument except those that implement cats, which are instead incorporated from the second argument.
Remarks: If cats is equal to locale​::​none, the resulting locale has a name if and only if the first argument has a name.
Otherwise, the resulting locale has a name if and only if the first two arguments both have names.
const locale& operator=(const locale& other) noexcept;
Effects: Creates a copy of other, replacing the current value.
Returns: *this.