[Edu-sig] PEP 238 - non-integer division

[Kirby Urner]

At 12:24 PM 7/26/2001 -0700, Kirby Urner wrote:


>>languages.  This is especially troublesome since python is so often used 
>>in a hybrid C or Java environment.
>
>To argue the other side, C and Java both require you to
>explicity declare the type of your variable, and the
>rules of coercian tell you, in the code itself, when
>a change is happening.  But in Python, I have much less
>to go on when trying to track types, especially when
>user input is considered.  So there's something to be
>said for forcing a type where you might be in doubt
>given lack of knowledge about the args.


Last point, then I'll shut up re this thread:  you might
counter that by my argument a + b is as potentially
ambiguous as a/b, as we don't necessarily know the types
of a, b in either case, going in.  That's true, but the
core point to realize is that where ints and floats are
concerned, a + b doesn't lose info (longs are another
story).

The problem with / is that it might lose info without
telling us.  b*(a/b) might not give us something close
to a, whereas b+(a-b) always will return a (if a,b = int
and/or floats).

So the point is, when pushing ambiguous types through
a potentially lossy operator, do we want to have an
ambiguous or unambiguous result?  The proposed design
change opts for the latter.  It's a reality check to
make up for the weak typing of variables, the difficulty
of tracking, lexically, the types of args involved.

I think Arthur points too much emphasis on someone
writing their own programs and following the unambiguous
rules in the tutorial, vs. someone inheriting code written
by others, and trying to puzzle out what's going on.
The pro programmer (paid) is as likely to be in the
latter situation as the former.  It's the readability
of code that we're after, long after the original
coders are out of the picture, not just how easy it
is to dash off something and have it do what you want
(that's programming for self alone as reader, and is
the hallmark of non-professional coding).

Kirby