Re: Ada.Numerics, Accuracy of trigonometric functions

[Dennis Lee Bieber <wlfraed@ix.netcom.com>]

On Fri, 7 Oct 2016 17:19:09 +0200, Markus Schöpflin <no.spam@spam.spam>
declaimed the following:

>Am 07.10.2016 um 16:52 schrieb Dennis Lee Bieber:
>> On Fri, 7 Oct 2016 12:13:48 +0200, Markus Schöpflin <no.spam@spam.spam>
>> declaimed the following:
>>
>>
>>> X = 4294967296.00000; COS(X) =  1.00000      <-- WHAT?
>>
>> 	That kind of surprises me...  Not the cos() result, but the input X
>>
>> 	Short float should only have around 23-24 bits of significance in the
>> mantissa -- enough for around 7 decimal digits. Yet you are seeing the full
>> UNSIGNED 32-bit integer value with a stack of fractional zeros tacked on.
>>
>> 	I'm tempted to think the compiler, not the run-time, is computing the
>> 2^32 as a universal (or whatever the preferred term is)  constant using the
>> smallest data type that holds the full value.
>>
>
>2**32 has an exact representation as short float: 0x4f800000 (in binary this 
>is 0 10011111 00000000000000000000000; sign 0, exponent 159, mantissa 0).
>
>Markus

	Ah... One of those magic numbers then...
-- 
	Wulfraed                 Dennis Lee Bieber         AF6VN
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