Generic interval parser

x::interval is a template class for generic parsing of multidimensional numeric values, using localized strings as dimension names. This template class is used by other interval string parsers, but is useful enough for other purposes.

#include <x/locale.H>
#include <x/messages.H>
#include <x/interval.H>

x::locale en_us(x::locale::create("en_us.UTF-8"));

x::messages msgcat(x::messages::create(en_us), "application");

static const char *const units[]={"block", "blocks",
                                  "section", "sections",
                                  "lot", "lots",

x::interval<int> i(units, 0, msgcat);

std::vector>int< value(i.parse("3 blocks, 1 section, 1 lot"));

The first parameter to x::interval's constructor is a read-only array of strings. The number of strings must be even, and the last one followed by a null pointer. Each pair of strings specifies the name of a dimension, in the single and plural form. The single and the plural form is used to look up the localized dimensional name in the message catalog. The above example passes an array of six strings, or three dimensions. The second aprameter to the constructor is the 0-based index of the default dimension. In the above example the default dimension parameter may be between 0 and 2, inclusive.

parse() parses a character string, which must consists of pair of names and values. Each value gets associated with a dimension specified by the name. The value may appear before or after the corresponding name. parse() places each value in a vector sized to the number of dimensions, with the value being placed in the appropriate index in the vector. The above example returns a vector of three values: element 0 is the block value, element 1 is the section value, element 2 is the lot value. If the parsed string does not specify a value for some particular dimension, its value is 0. If the parsed string consists of a single numeric value, without a dimension name, the default dimension index specifies its dimension, and the corresponding vector element.