0.3 - 0.2 == 0.2 - 0.1 is falsy. Which language gets this right?

Re:0.3 - 0.2 == 0.2 - 0.1 is falsy. Which language gets this... by beagle3 on Thursday October 04, 2012 @02:02PM (#4613508)

But the APL family (APL, J, K) does get this right despite using IEEE 754 floating point - it has comparison tolerance built in.

And you would probably look at what it does with disgust, given that it breaks transitivity of equality (that is, there are numbers such that a==b and b==c but a<>c). However, in practice it does work very well. You can still run into weird corners, but e.g.

    (3*(a/3.0))==a

always holds true, unlike with C comparison semantics.

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Re:0.3 - 0.2 == 0.2 - 0.1 is falsy. Which language gets this... by anonymouz on Thursday October 04, 2012 @03:11PM (#4613827)

This seems to be a very sensible default way to handle the comparison, assuming the programmer already knows about the problems with floating point math. A programmer who does not know about that will probably trip up sooner or later no matter how the language implements comparison.

So personally I would not see it as "right" (or "wrong"), simply because it is a choice between many different methods with their own advantages and disadvantages. I view this not as a problem a language can (or has to) solve, but as one a programmer has to be aware of and has to solve depending on his particular application.

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