qobject: Explain how QNum works, and why

    QNUM_DOUBLE

} QNumKind;

/*

 * QNum encapsulates how our dialect of JSON fills in the blanks left

 * by the JSON specification (RFC 7159) regarding numbers.

 *

 * Conceptually, we treat number as an abstract type with three

 * concrete subtypes: floating-point, signed integer, unsigned

 * integer.  QNum implements this as a discriminated union of double,

 * int64_t, uint64_t.

 *

 * The JSON parser picks the subtype as follows.  If the number has a

 * decimal point or an exponent, it is floating-point.  Else if it

 * fits into int64_t, it's signed integer.  Else if it fits into

 * uint64_t, it's unsigned integer.  Else it's floating-point.

 *

 * Any number can serve as double: qnum_get_double() converts under

 * the hood.

 *

 * An integer can serve as signed / unsigned integer as long as it is

 * in range: qnum_get_try_int() / qnum_get_try_uint() check range and

 * convert under the hood.

 */

typedef struct QNum {

    QObject base;

    QNumKind kind;