From: Kent Dahl <kentda@...>
Date: 2001-08-02T04:58:02+09:00
Subject: [ruby-talk:18990] Re: "Bang" versions of numerical methods on non-immediate values [was:  Numbers classes.. Rational number? ]

Yukihiro Matsumoto wrote:
> immediate values (fixnums and symbols) cannot be modified from method,
> so you cannot implement any bang method for fixnums.  You need
> assignment to alter value in a variable.

So for this to work for all numeric objects, we'd need a bang version of
an operator short-cut such as *= and friends? That would look bad:
	a *!= 2
Ok, so chuck that part of the idea in the bin. :-)
Would it be difficult to add support to the Ruby interpreter itself to
do add! methods "magically" on the variables, as a way to do the
assignment behind the users back? Basically writing the *!= nicely?
 
> You want
> 
> |       a = b = 1
> |       a.add!(1)       # a==2 and b==1, due to immediate values
> 
> but since 1 is a fixnum, thus the value of a cannot be changed.
> Considering this fact and that fixnums are most common numeric, bang
> method for numeric is not a good idea.

I mostly wanted to have it in Numeric to be consistent across all
numeric objects, and making it transparent for the user, for instance
when his variable goes from containing a fixnum to a bignum. But in
light of your feedback and the inconsistencies it would introduce, I'll
forget about fixnums for now.

So, my secondary, trimmed version of the idea:
Add add! and friends for Bignum, Float (and Rational?) etc only,
forgetting about fixnums.
Then I could create one accumulator number before a loop using
induced_from:

	a = Float.induced_from(0)
	(1...1000).each{ |i| a.add!( 1.0 ) }

Basically what I'm looking for, is a way of using Float (and Bignum etc)
as close as possible to a double* in C, a wrapper to a value, since the
I'm not too fond of the number of babies Float objects make when they do
math :-)

-- 
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