Author jaredgrubb
Recipients alexandre.vassalotti, amaury.forgeotdarc, christian.heimes, eric.smith, gvanrossum, jaredgrubb, mark.dickinson, nascheme, noam, preston, rhettinger, tim.peters
Date 2009-04-07.21:02:00
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Message-id <1239138123.55.0.585460045597.issue1580@psf.upfronthosting.co.za>
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The process that you describe in msg85741 is a way of ensuring
"memcmp(&x, &y, sizeof(x))==0", and it's portable and safe and is the
Right Thing that we all want and expect. But that's not "x==y", as that
Sun paper explains. It's close, but not technically accurate, as the
implication arrow only goes one way (just as "x=1/y" implies "xy=1" in
algebra, but not the other way around)

I'd be interested to see if you could say that the Python object
model/bytecode interpretation enforces a certain quauntum of operations
that actually does imply "eval(repr(x))==x"; but I suspect it's
unprovable, and it's fragile as Python grows to have more support in
CLI/LLVM/JVM backends. 

My pedantic mind would strip any and all references to floating-point
equality out of the docs, as it's dangerous and insidiously misleading,
even in "obvious" cases. But, I'll stop now :) (FYI: I've enjoyed the
~100 messages here.. Great stuff!)
History
Date User Action Args
2009-04-07 21:02:04jaredgrubbsetrecipients: + jaredgrubb, gvanrossum, tim.peters, nascheme, rhettinger, amaury.forgeotdarc, mark.dickinson, eric.smith, christian.heimes, alexandre.vassalotti, noam, preston
2009-04-07 21:02:03jaredgrubbsetmessageid: <1239138123.55.0.585460045597.issue1580@psf.upfronthosting.co.za>
2009-04-07 21:02:02jaredgrubblinkissue1580 messages
2009-04-07 21:02:01jaredgrubbcreate