Re: [Qemu-devel] [PATCH 04/21] qobject: add quint type

[Eric Blake]

On 03/13/2017 02:15 AM, Markus Armbruster wrote:
> Eric Blake <address@hidden> writes:
> 
>> On 03/11/2017 07:22 AM, Marc-André Lureau wrote:
>>> The type is not used at all yet. Add some tests to exercice it.
>>
>> s/exercice/exercise/
>>
>> I wonder if we need this patch at all.
>>
>> I've been thinking about a possible alternative representation, such
>> that a single QInt type can cover _both_ signed and unsigned types, by
>> having QInt track a sign bit bool in addition to a uint64_t value.
>>

> You say you've been thinking about extending QInt's range to cover
> uint64_t.  I've been thinking even more radically: replace both QInt and
> QFloat by QNumber.  This is how JSON *actually* works.
> 
> The new QNumber type provides constructors from double, int64_t and
> uint64_t.  It also provides conversion functions to double, int64_t and
> uint64_t.  The latter two can fail.

Interesting - I like it, as it takes my idea and goes one step further.
You'd want to track 64 bits of precision rather than just 53, when the
input was integral, but the idea seems to have some merit (we have some
special case in the testsuite for what happens in alternates with
various combinations of 'number' vs. 'int' that may need tweaking when
they are no longer distinguishable as QInt vs QFloat, but that's not too
onerous).

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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