From: Joel VanderWerf <vjoel@...>
Date: 2009-09-19T16:28:42+09:00
Subject: [ruby-core:25646] Re: [Bug #2121] mathn/rational destroys Fixnum#/, Fixnum#quo and Bignum#/, Bignum#quo

Charles Nutter wrote:
> The mathn library replaces Fixnum#/ and Bignum#/ causing them to
> return a different value. When the result of a division is not an
> integral value, the default versions will return 0. I can think of
> many algorithms that would use this expectation, and most other
> languages will not upconvert integral numeric types to floating-point
> or fractional types without explicit consent by the programmer.
> 
> When requiring 'mathn', Fixnum#/ and Bignum#/ are replaced with
> versions that return a fractional value ('quo') causing a core math
> operator to return not just a different type, but *a different
> value*.
> 
> No core library should be allowed to modify the return value of core
> numeric operators, or else those operators are worthless; you can't
> rely on them to return a specific value *ever* since someone else
> could require 'mathn' or 'rational'.

Perhaps it should be the responsibility of users of numeric operators to 
#floor explicitly when that is the intent, rather than rely on the 
(mostly standard, sometimes convenient, but questionable) 1/2==0 
behavior. Doing so would make it easier to adapt the code to float, 
rational, or other numeric types.

In your proposal, would Rational(1,3) be the preferred notation, since 
1/3==0? Or would there be something else, 1//3 or ...?

I've always thought of mathn as a kind of alternate ruby, not just 
another core library, hence to be used with caution...

-- 
       vjoel : Joel VanderWerf : path berkeley edu : 510 665 3407