On Sat, Sep 5, 2020 at 3:39 PM Cade Brown <brown.c...@gmail.com> wrote:
> The fact that so many modules and packages must define an 'inf' is, to me,
> a signal that such a constant WOULD be useful. All of them (should) be
> referring to the same value, anyways, so why not make a global constant
> instead?
>
`pi` is a widely used constant that is defined in both numpy and math. `e`
is a widely used constant that is defined in both numpy and math. Neither
of them is included in builtins. What is different about `inf` or
`Infinity`?
The only real goal I've seen is that you hope that `x == eval(repr(x))` for
floating point numbers. But that is doomed to failure since it cannot work
for NaN by its very definition. So with your change the situation would
be: It doesn't work for floats in general, but it works for two additional
floating point values that it didn't used to work for.... and even that
only means that you don't want to type one import:
>>> from math import inf
>>> inf == eval(repr(inf))
True
Lots of people have noted that being able to eval a repr is only a vague
goal in Python, that works *often* at most.
---
Now if you want something genuinely useful, I wish we had an integer
infinity. There are places where `float('inf')` just isn't suitable
because of the wrong type.
Doing a grep of CPython source, it looks like `sys.maxsize` occurs 343
times, and in almost every one of them it is a stand-in for "infinity." I
am certain there are other places where "a big number" is used because no
integer infinity exists; sys.maxsize is only one spelling of that.
The general context where I'd want it is in code like this:
last = int.Infinity if not n:=smaller_last() else n
good_stuff = all_stuff[first:last+1]
Or in a similar spirit, we might be looking for a bound, and run `bound =
min(new_thing, bound)` in a loop. For that code, I need an initial value;
albeit, in that case, float inf is probably fine. And if I'm writing code
to count the number of books on my shelf, sys.maxsize is a perfectly good
starting point as well. But int.Infinity expresses the actual intention
more clearly.
--
The dead increasingly dominate and strangle both the living and the
not-yet born. Vampiric capital and undead corporate persons abuse
the lives and control the thoughts of homo faber. Ideas, once born,
become abortifacients against new conceptions.
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