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Message-ID: <4AFD67C4.9070100@codemonkey.ws>
Date: Fri, 13 Nov 2009 08:05:56 -0600
From: Anthony Liguori <anthony@codemonkey.ws>
MIME-Version: 1.0
Subject: Re: [Qemu-devel] [PATCH 3/3] Add test suite for json marshalling
References: <1257967478-4847-1-git-send-email-aliguori@us.ibm.com>	<1257967478-4847-3-git-send-email-aliguori@us.ibm.com>
	<20091113031431.GF19405@shareable.org>
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To: Jamie Lokier <jamie@shareable.org>
Cc: Anthony Liguori <aliguori@us.ibm.com>, qemu-devel@nongnu.org, Luiz Capitulino <lcapitulino@redhat.com>

Jamie Lokier wrote:
> Anthony Liguori wrote:
>   
>> After checking that we can demarshal, marshal again and compared to
>> the expected decoded value.  This doesn't work so well for floats
>> because they cannot be accurately represented in decimal but we try
>> our best.
>>     
>
> Good sprintf/scanf/strtod implementations do guarantee that what's
> printed and then parsed gets back the same floating point value, as
> long as you have printed sufficient decimal digits.
>
> I'm not sure if FLT_DIG/DLB_DIG are the right number of digits,
> though.  Glibc's documentation of those is confusing and they might
> mean something a little different.
>   

Eh, I played around quite a bit and the results were disappointing.

$ printf "%f\n" 43.32
43.320000
$ printf "%0.32f\n" 43.32
43.31999999999999999972244424384371

Regards,

Anthony Liguori
> -- Jamie
>
>
>