Qi ushort_?

Hello,

What is this, exactly? I'm not sure I fully understand from the
documentation, and the parameters _0_, _1_, etc, aren't very
descriptive.

http://www.boost.org/doc/libs/1_65_1/libs/spirit/doc/html/spirit/qi/reference/numeric/uint.html

Am I specifying either a precise value? Or the range? Is the default
the full range? i.e.

using namespace std;
using namespace boost::spirit::qi;

// ...
ushort_ // same as saying...
ushort_(numeric_limits<uint16_t>::min(), numeric_limits<uint16_t>::max())
/* or this in case you had to prove it to yourself */ ushort_(0, 65535)

If so, that would be far simpler than taking a more circuitous route.
Just thank goodness port numbers, in this case, aren't 64-bit or even
32-bit unsigned integers.

Further than that, I'm not sure how these unit test assertions prove
exhaustively that this "works". They show alternatives, and that not
exhaustively, either. But not 0-65535, to be clear.

BOOST_TEST(test("123", ushort_(0) | ushort_(123)));
BOOST_TEST(test("123", ushort_(123) | ushort_(0)));

i.e.

_port_rule = (
    (char_('0'))
    | (char_('1', '5') >> -(digit >> -(digit >> -(digit >> -digit))))
    | (char_('6')
        >> -((char_('0', '4') >> -(digit >> -(digit >> -digit)))
            | (char_('5')
                >> -((char_('0', '4') >> -(digit >> -digit))
                    | (char_('5')
                        >> -((char_('0', '2') >> -digit)
                            | (char_('3') >> -char_('0', '5'))
                            | (char_('4', '9'))
                            ))
                    | (char_('6', '9') >> -digit)
                    ))
            | (char_('6', '9') >> -(digit >> -digit))
            )
        )
    | (char_('7', '9') >> -(digit >> -(digit >> -digit))))
    ;

Tested across the full range of 0-65535, including absurdly incorrect
use cases, negative numbers, non-digit character strings, floating
point string representations.

Looking at a migration path forward, does the same thing exist for X3?

Cheers,

Michael Powell

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