[Python-ideas] Approximately equal operator

[Antoine Pitrou]

On Fri, 15 Jun 2018 14:38:22 -0300
Andre Roberge <andre.roberge at gmail.com>
wrote:
> 
> Here's a sample session for demonstration purpose...
> 
> $ python -m experimental
> experimental console version 0.9.5. [Python version: 3.6.1]
> 
> ~~> 0.1 + 0.2  
> 0.30000000000000004
> ~~> 0.1 + 0.2 == 0.3  
> False
> ~~> from __experimental__ import approx
> ~~> 0.1 + 0.2 ~= 0.3    # use approximately equal operator  
> True
> ~~> 0.1 + 0.2 <~= 0.3  
> True
> ~~> 0.1 + 0.2 >~= 0.3  
> True
> ~~> 2 ** 0.5  
> 1.4142135623730951
> ~~> 2**0.5 ~= 1.414  
> False
> ~~> set_tols(0.001, 0.001)
> ~~> 2**0.5 ~= 1.414  
> True

On the one hand, this matches the corresponding math notation quite
pleasantly.  On the other hand, it doesn't seem so useful that it
deserves to be a builtin operator.  I'm also not sure we want to
encourage its use for anything other than experimenting at the prompt
and writing unit tests.

Being able to set a global tolerance setting is an anti-pattern IMHO,
regardless of the operator proposal.

Regards

Antoine.