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Re: NaN semantics

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From:
Damian Conway
Date:
October 8, 2001 23:39
Subject:
Re: NaN semantics
Message ID:
200110090639.QAA03876@indy05.csse.monash.edu.au
 
   > But I assume that == means numerically equal (and here I could be
   > wrong). If what I assume is true however, then anything which doesn't
   > have any numerical meaning, numerically compared to anything (even to
   > itself) should not return the misleading result that the two compared
   > values are numerically equal.
   > 
   > Then again, if you tell me that == operator doesn't mean "numerically
   > equal", I will agree that NaN==NaN should be true even considering that
   > 'cat'=='dog' will also be true.

But 'cat'=='dog' *is* true. Numerically, they *are* equal.
They are equally not numbers.  One should certainly get a warning
(and one will if warnings are enabled), but this 
expression shouldn't return false.

Sigh. I *do* see your point of view (Laziness), but I still have immense
difficulty with the notion that:

        $x == NaN

doesn't return true if $x contains NaN.

Damian

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