| Doc No: | WG21 N2842 = 09-0032 |
| Date: | 2009-04-01 |
| Reply to: | Bill Seymour <stdbill.h@pobox.com> |
the first of April, two thousand nine
Because many current C++ implementations don’t have
To show that generating text for very large numbers is also possible,
the demo has a page that will generate
The author would like to thank (in
class numtext_base {
public:
enum inflection {
none = 0x0000,
// ...
cardinal = 0x0000,
ordinal = 0x8000,
};
};
We’ll have a non-template base class with bitmasks for the
various inflections that we might need.
At a minimum, even in the “C” locale, we’d
want to produce both cardinal and ordinal numbers; and other
locales will have additional requirements. In Danish, for example,
both the cardinal 1 and the ordinal 2 have gender
(en-et, anden-andet). In German,
the ordinals are considered adjectives with number, gender,
and case; there are three
complete sets of adjective declensions; and although there is a word for the cardinal 1
(eins), it is often replaced by the indefinite article
(ein-eines-einem-…).
template<class charT>
class numtext : public locale::facet, public numtext_base {
public:
// ...
void convert(basic_string<charT>&, uintmax_t, inflection = none) const;
};
Like codecvt<> and similar facets, numtext<>
doesn’t actually do I/O. Instead, it just returns the correct
text in a basic_string<> passed by The second argument, the number to convert, can be any unsigned integer that the C++ implementation can handle. Having many functions overloaded on the integer type wouldn’t have any noticeable effect on efficiency since the time it takes to generate the text would certainly swamp whatever it takes to promote the value to uintmax_t.
The optional third argument specifies the inflection. It defaults to producing uninflected cardinal numbers.
One or both of two additional overloads on the second argument, perhaps some user-defined type with integer semantics (presumably a bignum of some sort), or maybe a basic_string<> of digits, would serve to extend the range. These overloads are not proposed by this paper, but could be considered for a TR.
namespace std {
class numtext_base {
public:
enum inflection {
none = 0x0000,
number = 0x0003,
singular = 0x0000,
dual = 0x0001,
plural = 0x0002,
// = 0x0003,
gender = 0x000C,
common = 0x0000,
masculine = 0x0004,
feminine = 0x0008,
neuter = 0x000C,
lexcase = 0x00F0,
nominative = 0x0000,
genitive = 0x0010,
dative = 0x0020,
accusative = 0x0030,
oblative = 0x0040,
vocative = 0x0050,
locative = 0x0060,
ergative = 0x0070,
absolutive = 0x0080,
direct = 0x0090,
instrumental = 0x00A0,
prepositional = 0x00B0,
// = 0x00C0,
// = 0x00D0,
// = 0x00E0,
// = 0x00F0,
strength = 0x0300, // Sometimes, adjectives can be declined
strong = 0x0000, // more weakly if there’s another word in
mixed = 0x0100, // the phrase, like a definite article,
weak = 0x0200, // that provides the information.
// = 0x0300,
scale = 0x0C00, // In English, is 10**9
amer = 0x0000, // a billion,
euro = 0x0400, // a milliard,
olduk = 0x0800, // or a thousand million?
// = 0x0C00,
// bits 0x7000 unused so far
cardinal = 0x0000,
ordinal = 0x8000,
};
};
//
// The facet itself is unsurprising:
//
template<class charT>
class numtext : public locale::facet, public numtext_base {
public:
typedef charT char_type;
typedef basic_string<charT> string_type;
explicit numtext(size_t refs = 0) : locale::facet(refs) { }
void convert(string_type& dest, uintmax_t val, inflection i = none) const
{
do_convert(dest, val, i);
}
static locale::id id;
protected:
~numtext() { }
virtual void do_convert(string_type&, uintmax_t, inflection) const = 0;
};
} // namespace std
(You can download the current implementation’s source code
as .tar.gz
or .zip.
For the purposes of the demo, the leaf classes have public,
static