Using fractions instead of floats

[Neil Cerutti]

On 2007-10-02, Arnaud Delobelle <arnodel at googlemail.com> wrote:
> On Oct 2, 12:42 pm, Neil Cerutti <horp... at yahoo.com> wrote:
>> On 2007-10-01, Arnaud Delobelle <arno... at googlemail.com> wrote:
>> > Scheme has prefix numeric operators, so that 1/2 is
>> > unambiguously (for the interpreter and the user) a litteral for
>> > 'the fraction 1/2'. You can't avoid the confusion in python, as
>> > binary operators are infix. Of course, we could create a new
>> > kind of litteral.  Let's see, / and // are already operators,
>> > so why not use /// ? ;)
>>
>> But you wouldn't actually need a literal rational represention.
>
> In which case rationals are better off in a module than in the
> language!

I was supposing that 1/2 would result in a rational number, which
would require language support, whether it's a literal rational
number or a division of two integer constants.

>> But I'm just playing Devil's Advocate here; I like rationals
>> in Scheme and Lisp, but I don't see a need for them in Python.
>
>> On the other hand, Python has had complex numbers a long time,
>> and it doesn't need those more than rationals, does it? My
>> guess is that it got complex numbers but not rationals because
>> rationals just aren't very efficient.
>
> Another guess could be that real numbers being closed under the
> four arithmetic operations, there is no danger to accidentally
> step into complex numbers. OTOH floats and rationals are two
> (conflicting) ways of extending integers.

You would have to adopt a few simple conversion rules, a la
Scheme. Inexact numbers are contagious, for example. It was
pretty shocking for a Scheme programmer to see the gmpy package
break that rule. ;)

> I use rationals a lot, and I don't want them in the language :)

Fair enough.

-- 
Neil Cerutti
The pastor will preach his farewell message, after which the choir will sing,
"Break Forth Into Joy." --Church Bulletin Blooper