Re: NSNumber stringValue
Re: NSNumber stringValue
- Subject: Re: NSNumber stringValue
- From: Andrew Farmer <email@hidden>
- Date: Sat, 12 Dec 2009 15:57:37 -0800
On 12 Dec 2009, at 09:32, Ben Haller wrote:
>>> You should not compare floating point numbers for equality in most cases. This is true of any language on any platform.
>>
>> Indeed, some floating-point numbers (such as the one represented by the integer 0x7fc00000) will compare as not equal to themselves:
>
> I think what the OP really wanted to know (and I'm interested in the answer too) is whether going out to the stringValue and back to the doubleValue is guaranteed to yield a float that is bitwise identical to the original float, or whether there is "drift" in the least significant bit or two due to the changes in representation. Anyway, even if that's not the OP meant, that's what I'd like to ask. :->
Nope, there are trivial counterexamples there too. All NaNs stringify to "nan", for instance, and all infinities stringify to either "inf" or "-inf", depending on sign.
(And, even if you only care about finite numbers, Andy Lee has an excellent counterexample for that as well.)_______________________________________________
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