locale2.html

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<P><B><CODE><A HREF="#locale::category">category</A>
&#183; <A HREF="#locale::classic">classic</A>
&#183; <A HREF="#locale::combine">combine</A>
&#183; <A HREF="#locale::facet">facet</A>
&#183; <A HREF="#locale::global">global</A>
&#183; <A HREF="#locale::id">id</A>
&#183; <A HREF="#locale::locale">locale</A>
&#183; <A HREF="#locale::name">name</A>
&#183; <A HREF="#locale::operator!=">operator!=</A>
&#183; <A HREF="#locale::operator()">operator()</A>
&#183; <A HREF="#locale::operator==">operator==</A>
</CODE></B></P>
<HR>

<PRE>class <B>locale</B> {
public:
    class <B><A HREF="#locale::facet">facet</A></B>;
    class <B><A HREF="#locale::id">id</A></B>;
    typedef int <B><A HREF="#locale::category">category</A></B>;
    static const category <B>none</B>, <B>collate</B>, <B>ctype</B>, <B>monetary</B>,
        <B>numeric</B>, <B>time</B>, <B>messages</B>, <B>all</B>;
    <B><A HREF="#locale::locale">locale</A></B>();
    explicit <B><A HREF="#locale::locale">locale</A></B>(const char *locname);
    <B><A HREF="#locale::locale">locale</A></B>(const locale&amp; loc, const locale&amp; other,
        category cat);
    <B><A HREF="#locale::locale">locale</A></B>(const locale&amp; loc, const char *locname, category cat);
    template&lt;class Facet&gt;
        <B><A HREF="#locale::locale">locale</A></B>(const locale&amp; loc, Facet *fac);
    template&lt;class Facet&gt;
        locale <B><A HREF="#locale::combine">combine</A></B>(const locale&amp; loc) const;
    template&lt;class Elem, class Tr, class Alloc&gt;
        bool <B><A HREF="#locale::operator()">operator()</A></B>(const basic_string&lt;Elem, Tr, Alloc&gt;&amp; left,
            const basic_string&lt;Elem, Tr, Alloc&gt;&amp; right) const;
    string <B><A HREF="#locale::name">name</A></B>() const;
    bool <B><A HREF="#locale::operator==">operator==</A></B>(const locale&amp; right) const;
    bool <B><A HREF="#locale::operator!=">operator!=</A></B>(const locale&amp; right) const;
    static locale <B><A HREF="#locale::global">global</A></B>(const locale&amp; right);
    static const locale&amp; <B><A HREF="#locale::classic">classic</A></B>();
    };</PRE>

<P>The class describes a
<B><A NAME="locale object">locale object</A></B> that encapsulates a
<A HREF="locale.html#locale">locale</A>. It represents
culture-specific information as a list of
<B><A NAME="locale facet">facets</A></B>. A facet is a
pointer to an object of a class
derived from class <CODE><A HREF="#locale::facet">facet</A></CODE>
that has a public object of the form:

<PRE>static locale::id id;</PRE>

<P>You can define an open-ended set of these facets. You can also
construct a locale object that designates an arbitrary number of
facets.</P>

<P>Predefined groups of these facets represent the
<A HREF="locale.html#locale category">locale categories</A>
traditionally managed in the Standard C library by the function
<CODE><A HREF="locale.html#setlocale">setlocale</A></CODE>.</P>

<P>Category <B><CODE><A HREF="#locale::collate">collate</A></CODE></B>
(<CODE><A HREF="locale.html#LC_COLLATE">LC_COLLATE</A></CODE>)
includes the facets:</P>

<PRE>collate&lt;char&gt;
collate&lt;wchar_t&gt;</PRE>

<P>Category <B><CODE><A HREF="#locale::ctype">ctype</A></CODE></B>
(<CODE><A HREF="locale.html#LC_CTYPE">LC_CTYPE</A></CODE>)
includes the facets:</P>

<PRE>ctype&lt;char&gt;
ctype&lt;wchar_t&gt;
codecvt&lt;char, char, mbstate_t&gt;
codecvt&lt;wchar_t, char, mbstate_t&gt;</PRE>

<P>Category <B><CODE><A HREF="#locale::monetary">monetary</A></CODE></B>
(<CODE><A HREF="locale.html#LC_MONETARY">LC_MONETARY</A></CODE>)
includes the facets:</P>

<PRE>moneypunct&lt;char, false&gt;
moneypunct&lt;wchar_t, false&gt;
moneypunct&lt;char, true&gt;
moneypunct&lt;wchar_t, true&gt;
money_get&lt;char, istreambuf_iterator&lt;char&gt; &gt;
money_get&lt;wchar_t, istreambuf_iterator&lt;wchar_t&gt; &gt;
money_put&lt;char, ostreambuf_iterator&lt;char&gt; &gt;
money_put&lt;wchar_t, ostreambuf_iterator&lt;wchar_t&gt; &gt;</PRE>

<P>Category <B><CODE><A HREF="#locale::numeric">numeric</A></CODE></B>
(<CODE><A HREF="locale.html#LC_NUMERIC">LC_NUMERIC</A></CODE>)
includes the facets:</P>

<PRE>num_get&lt;char, istreambuf_iterator&lt;char&gt; &gt;
num_get&lt;wchar_t, istreambuf_iterator&lt;wchar_t&gt; &gt;
num_put&lt;char, ostreambuf_iterator&lt;char&gt; &gt;
num_put&lt;wchar_t, ostreambuf_iterator&lt;wchar_t&gt; &gt;
numpunct&lt;char&gt;
numpunct&lt;wchar_t&gt;</PRE>

<P>Category <B><CODE><A HREF="#locale::time">time</A></CODE></B>
(<CODE><A HREF="locale.html#LC_TIME">LC_TIME</A></CODE>)
includes the facets:</P>

<PRE>time_get&lt;char, istreambuf_iterator&lt;char&gt; &gt;
time_get&lt;wchar_t, istreambuf_iterator&lt;wchar_t&gt; &gt;
time_put&lt;char, ostreambuf_iterator&lt;char&gt; &gt;
time_put&lt;wchar_t, ostreambuf_iterator&lt;wchar_t&gt; &gt;</PRE>

<P>Category <B><CODE><A HREF="#locale::messages">messages</A></CODE></B>
(<CODE>LC_MESSAGES</CODE>) includes the facets:</P>

<PRE>messages&lt;char&gt;
messages&lt;wchar_t&gt;</PRE>

<P>(The last category is required by Posix, but not the C Standard.)</P>

<P>Some of these predefined facets are used by the
<A HREF="lib_cpp.html#iostreams">iostreams</A> classes,
to control the conversion of numeric values to and from
text sequences.</P>

<P>An object of class <CODE>locale</CODE> also stores a
<B><A NAME="locale name">locale name</A></B> as an object of class
<CODE><A HREF="string2.html#string">string</A></CODE>. Using an
invalid locale name to construct a
<A HREF="#locale facet">locale facet</A> or a locale object
throws an object of class
<CODE><A HREF="stdexcep.html#runtime_error">runtime_error</A></CODE>.
The stored locale name is <CODE>"*"</CODE> if the locale object
cannot be certain that a C-style locale corresponds exactly
to that represented by the object. Otherwise, you can establish
a matching locale within the Standard C library,
for the locale object <CODE>loc</CODE>, by calling
<CODE><A HREF="locale.html#setlocale">setlocale</A>(
<A HREF="locale.html#LC_ALL">LC_ALL</A>,
loc.<A HREF="#locale::name">name</A>.
<A HREF="string2.html#basic_string::c_str">c_str</A>())</CODE>.</P>

<P>In this
<A HREF="index.html#implementation">implementation</A>,
you can also call the static member function:</P>

<PRE>static locale <B><A NAME="locale::empty">empty</A></B>();</PRE>

<P>to construct a locale object that has no facets. It is also a
<B><A NAME="transparent locale">transparent locale</A></B> --
if the template functions
<CODE><A HREF="#has_facet">has_facet</A></CODE> and
<CODE><A HREF="#use_facet">use_facet</A></CODE> cannot find
the requested facet in a transparent locale, they consult first the
<A HREF="#global locale">global locale</A> and then,
if that is transparent, the
<A HREF="#classic locale">classic locale</A>. Thus, you can write:</P>

<PRE>cout.imbue(locale::empty());</PRE>

<P>Subsequent insertions to
<CODE><A HREF="iostream.html#cout">cout</A></CODE> are
mediated by the current state of the global locale.
You can even write:</P>

<PRE>locale loc(locale::empty(), locale::classic(),
    locale::numeric);
cout.imbue(loc);</PRE>

<P>Numeric formatting rules for subsequent insertions to
<CODE>cout</CODE> remain the same as in the
<A HREF="locale.html#C locale">C locale</A>,
even as the global locale supplies changing rules for inserting
dates and monetary amounts.</P>

<H3><CODE><A NAME="locale::category">locale::category</A></CODE></H3>

<PRE>typedef int <B>category</B>;
static const category <B>none</B>, <B>collate</B>, <B>ctype</B>, <B>monetary</B>,
    <B>numeric</B>, <B>time</B>, <B>messages</B>, <B>all</B>;</PRE>

<P>The type is a synonym for <I>int</I> so that it can represent
any of the C <A HREF="locale.html#locale category">locale categories</A>.
It can represent a group of distinct elements of a
<A HREF="lib_cpp.html#bitmask type">bitmask type</A>
(which is anonymous) local to class <CODE>locale</CODE>.
The elements are:</P>

<UL>
<LI><B><CODE><A NAME="locale::collate">collate</A></CODE></B>,
corresponding to the C category
<CODE><A HREF="locale.html#LC_COLLATE">LC_COLLATE</A></CODE></LI>

<LI><B><CODE><A NAME="locale::ctype">ctype</A></CODE></B>,
corresponding to the C category
<CODE><A HREF="locale.html#LC_CTYPE">LC_CTYPE</A></CODE></LI>

<LI><B><CODE><A NAME="locale::monetary">monetary</A></CODE></B>,
corresponding to the C category
<CODE><A HREF="locale.html#LC_MONETARY">LC_MONETARY</A></CODE></LI>

<LI><B><CODE><A NAME="locale::numeric">numeric</A></CODE></B>,
corresponding to the C category
<CODE><A HREF="locale.html#LC_NUMERIC">LC_NUMERIC</A></CODE></LI>

<LI><B><CODE><A NAME="locale::time">time</A></CODE></B>,
corresponding to the C category
<CODE><A HREF="locale.html#LC_TIME">LC_TIME</A></CODE></LI>

<LI><B><CODE><A NAME="locale::messages">messages</A></CODE></B>,
corresponding to the Posix category
<CODE>LC_MESSAGES</CODE></LI>
</UL>

<P>In addition, two useful values are:</P>

<UL>
<LI><B><CODE><A NAME="locale::none">none</A></CODE></B>, corresponding to none of
the C categories</LI>

<LI><B><CODE><A NAME="locale::all">all</A></CODE></B>,
corresponding to the C union of all categories
<CODE><A HREF="locale.html#LC_ALL">LC_ALL</A></CODE></LI>
</UL>

<P>You can represent an arbitrary group of categories by ORing
these constants, as in <CODE>monetary | time</CODE>.</P>

<H3><CODE><A NAME="locale::classic">locale::classic</A></CODE></H3>

<PRE>static const locale&amp; <B>classic</B>();</PRE>

<P>The static member function returns a locale object that represents the
<B><A NAME="classic locale">classic locale</A></B>,
which behaves the same as the
<A HREF="locale.html#C locale">C locale</A> within the
Standard C library.</P>

<H3><CODE><A NAME="locale::combine">locale::combine</A></CODE></H3>

<PRE>template&lt;class Facet&gt;
    locale <B>combine</B>(const locale&amp; loc) const;</PRE>

<P>The member function returns a locale object that
replaces in (or adds to) <CODE>*this</CODE> the facet <CODE>Facet</CODE>
listed in <CODE>loc</CODE>.</P>

<H3><CODE><A NAME="locale::facet">locale::facet</A></CODE></H3>

<PRE>class <B>facet</B> {
protected:
    explicit <B>facet</B>(size_t refs = 0);
    virtual <B>~facet</B>();
private:
    <B>facet</B>(const facet&amp;)          // not defined
    <B>void operator=</B>(const facet&amp;) // not defined
    };</PRE>

<P>The member class serves as the base class for all
<A HREF="#locale facet">locale facets</A>. Note that you
can neither copy nor assign an object of class <CODE>facet</CODE>.
You can construct and destroy objects derived from class
<CODE>locale::facet</CODE>, but not objects of the base class proper.
Typically, you construct an object <CODE>myfac</CODE> derived
from <CODE>facet</CODE> when you construct a locale, as in:</P>

<PRE>locale loc(locale::classic(), new myfac);</PRE>

<P>In such cases, the constructor for the base class <CODE>facet</CODE>
should have a zero <CODE>refs</CODE> argument. When the object
is no longer needed, it is deleted. Thus, you supply a nonzero
<CODE>refs</CODE> argument only in those rare cases where you
take responsibility for the lifetime of the object.</P>

<H3><CODE><A NAME="locale::global">locale::global</A></CODE></H3>

<PRE>static locale <B>global</B>(const locale&amp; loc);</PRE>

<P>The static member function stores a copy of <CODE>loc</CODE> as the
<B><A NAME="global locale">global locale</A></B>. It also calls
<CODE><A HREF="locale.html#setlocale">setlocale</A>(
<A HREF="locale.html#LC_ALL">LC_ALL</A>,
loc.<A HREF="#locale::name">name</A>.
<A HREF="string2.html#basic_string::c_str">c_str</A>())</CODE>,
to establishing a matching locale within the Standard C library.
The function then returns the previous global locale. At
<A HREF="lib_over.html#program startup">program startup</A>,
the global locale is the same as the
<A HREF="#classic locale">classic locale</A>.</P>

<H3><CODE><A NAME="locale::id">locale::id</A></CODE></H3>

<PRE>class <B>id</B> {
protected:
    <B>id</B>();
private:
    <B>id</B>(const id&amp;)             // not defined
    <B>void operator=</B>(const id&amp;) // not defined
    };</PRE>

<P>The member class describes the static
member object required by each unique
<A HREF="#locale facet">locale facet</A>. Note that you
can neither copy nor assign an object of class <CODE>id</CODE>.</P>

<H3><CODE><A NAME="locale::locale">locale::locale</A></CODE></H3>

<PRE><B>locale</B>();
explicit <B>locale</B>(const char *locname);
<B>locale</B>(const locale&amp; loc, const locale&amp; other,
    category cat);
<B>locale</B>(const locale&amp; loc, const char *locname, category cat);
template&lt;class Facet&gt;
    <B>locale</B>(const locale&amp; loc, Facet *fac);</PRE>

<P>The first constructor initializes the object to match the
<A HREF="#global locale">global locale</A>. The second constructor
initializes all the
<A HREF="locale.html#locale category">locale categories</A> to have behavior
consistent with the <A HREF="#locale name">locale name</A>
<CODE>locname</CODE>. The remaining constructors copy <CODE>loc</CODE