Association

Hi guys,

I have another noob question :)

Why Association>>#= is not

= anAssociation

        ^self == anAssociation or: [super = anAssociation and: [value =  
anAssociation value]]

Because I can have strange behavior like

association := #foo -> Float nan.

{association} includes: association

answer false

:S


Thanks,


Ben

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I don't really know the answer, but it is not about the implementation
in Association. It is reasonable for associations to be equal if both
their key & value are equal. The problem as you have seen is Float nan
does not compare using #=.

Float nan = Float nan --> false

I don't the details but perhaps the clue is in the implementation of isNaN

isNaN
        "simple, byte-order independent test for Not-a-Number"

        ^ self ~= self

so something like this seems a better test

association := #foo -> Float nan.
{association} anySatisfy: [:each | each value isNaN]


cheers,
Mike

On Mon, Nov 15, 2010 at 3:06 PM, Benjamin
<[hidden email]> wrote:
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On Nov 16, 2010, at 9:20 AM, Michael Roberts wrote:


Thank you, it's a good clue :)
It's not really cool to have to add special code to test NaN, but if  
it's the only way ...

Ben

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On Tue, Nov 16, 2010 at 3:17 AM, Benjamin
<[hidden email]> wrote:
NaN is an extremely special case. According to some random forum
posting I ran across talking about ISO floating point standards, for
example, HUGE_FLOAT * 0 is undefined (which seems ridiculous to me,
but there's probably a good reason for it, if it's true...which is
really completely beside the point). It might be 0, or it might be
NaN. Would you really want that value (in general) to be considered
equal to 1/0?

In my mind, they've pretty much wound in the same category as SQL's NULL.
>
> Ben

-- James

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