[Python-ideas] PEP 485: A Function for testing approximate equality (original) (raw)

Ron Adam ron3200 at gmail.com
Wed Feb 11 16:27:11 CET 2015

On 02/10/2015 11:15 PM, Chris Barker wrote:

Large tolerances ----------------

The most common use case is expected to be small tolerances -- on order of the default 1e-9. However there may be use cases where a user wants to know if two fairly disparate values are within a particular range of each other: "is a within 200% (reltol = 2.0) of b? In this case, the string test would never

string -> strong "the strong test would never"

indicate that two values are within that range of each other if one of them is zero. The strong case, however would use the larger (non-zero) value for the

strong -> weak "The weak case, ..."

test, and thus return true if one value is zero. For example: is 0 within 200% of 10? 200% of ten is 20, so the range within 200% of ten is -10 to +30. Zero falls within that range, so it will return True.

-Ron

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