[Python-Dev] decimal API (original) (raw)

mcherm2 at mcherm.com mcherm2 at mcherm.com
Tue Jul 6 20:59:20 CEST 2004

Raymond writes:

For the alpha, I've left all of the traps off except for ConversionSyntax. The reasoning that the numeric model is otherwise self-contained. Dividing by zero usefully gives Infinity. NaNs result from non-sensical operations. NaNs can even have diagnositic information associated with them. Let's let people experience what the standard has to offer. [...] Though decimals play nice with many other Python tools, we shouldn't hide that the model is different and that many of those differences are for the better:

I guess I'm -0.5 on this... I object, but not strongly. I WILL go ahead and express my reasons for objecting, but if you don't find them convincing, then go ahead as planned and I won't complain.

Your list of ways that Decimal's model is better is an excellent list, but much of it doesn't apply to the question of whether the traps should default to on or off. I'll admit that the feature

is "invisible" if we turn on my prefered list of traps because you can't create a NaN or an Infinity. Obviously, the traps can easily be turned off, but that doesn't negate the fact that people will be more aware that Decimal supports NaN and Infinity if they get NaNs and Infinities while playing interactively.

The feature:

is pretty much a wash... if we turn traps ON people will have to read the docs to realize that signals can be ignored (and inspected after), and if we turn them OFF they'll have to read to realize that signals can RAISE.

The other features:

are all visible whether traps default to ON or OFF.

So in the end, we're talking about what we want to do for people who choose NOT to read the docs. And I submit that we want those people to get an exception, because when they try to do their task and they get an exception instead, they will then turn to the docs to decide how to fix it. But if we left traps OFF then these foolish people might see that their program had run to completion and then accept the results without even realizing that there was a way to check for signals.

-- Michael Chermide

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