Programming Horror

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God I wish there was an easier way to do this (programming.dev)

submitted 11 months ago* (last edited 11 months ago) by [email protected] to c/[email protected]

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[–] [email protected] 0 points 11 months ago (3 children)

Divide by 2 and check for a decimal point.

I mean, it ain't wrong.

[–] [email protected] 0 points 11 months ago (2 children)

You know, I was going to let this slide under the notion that we're just ignoring the limited precision of floating point numbers... But then I thought about it and it's probably not right even if you were computing with real numbers! The decimal representation of real numbers isn't unique, so this could tell me that "2 = 1.9999..." is odd. Maybe your string coercion is guaranteed to return the finite decimal representation, but I think that would be undecidable.

[–] [email protected] 0 points 11 months ago (1 children)

Ackchyually-- IEEE 754 guarantees any integer with absolute value less than 2^24 to be exactly representable as a single precision float. So, the "divide by 2, check for decimals" should be safe as long as the origin of the number being checked is somewhat reasonable.

[–] [email protected] 0 points 11 months ago

Of course, but it's somewhat nasty when all of a sudden is_even doesn't do what you expect :).