[Python-Dev] Expert floats (original) (raw)

Greg Ewing greg at cosc.canterbury.ac.nz
Tue Apr 6 21:58:33 EDT 2004


Andrew Koenig <ark-mlist at att.net>:

The reason is that the first example does arithmetic, and it is easy to explain that floating-point arithmetic is not completely accurate.

Then how would you explain this to them:

1.1 < 1.1000000000000001 False

There's no arithmetic being done there.

And if you're thinking of something like "floats don't have that many digits of precision", you then need to explain

1.2 < 1.2000000000000001 True

Greg Ewing, Computer Science Dept, +--------------------------------------+ University of Canterbury, | A citizen of NewZealandCorp, a | Christchurch, New Zealand | wholly-owned subsidiary of USA Inc. | greg at cosc.canterbury.ac.nz +--------------------------------------+



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