[ruby-core:28207] Re: [Bug #2756] Issues with Math and Complex behavior on 1.9

Hi!

> Q. Should 1.9 coerce arguments to Math methods?

I really want to agree, but it seems intended change for
prohibiting string:

  $ ruby18 -ve 'p Math.atanh("0.5")'
  ruby 1.8.8dev (2010-02-01 revision 26536) [i686-linux]
  0.549306144334055

  $ ./ruby -ve 'p Math.atanh("0.5")'
  ruby 1.9.2dev (2010-02-18 trunk 26703) [i686-linux]
  -e:1:in `atanh': can't convert String into Float (TypeError)
          from -e:1:in `<main>'

The root cause is that explicit float conversion and implicit
one are not distinguished.  There are to_i, to_int and to_f,
but no to_flo.
I think this can be fixed by adding to_flo in theory, but it
may change behavior of many methods that take Float as arg.
Needs much time to discuss, and the change is too big for 1.9
series.


> Q. Can we change the 1.8.7 behavior when raising exceptions to be both in=
ternally consistent and consistent with the behavior of 1.9 (Note that nume=
rous changes to the exception raised have already been made in 1.8.5 -> 1.8=
.6 -> 1.8.7, so this request is not without precedent.)

Shyouhei, please decide it.
IMO, TEENY version may accept such a small spec change, but
patch-level might not.


> Q. Should the behavior of atanh after requiring lib/complex.rb be the sam=
e for non-Complex inputs as before?

I agree in this case.
Ruby library generally tends to ignore such a type difference.
(see http://redmine.ruby-lang.org/issues/show/2495)
But cmath.rb attempts to replace the core Math module, so I
think it has a responsibility to behave as similarly as
possible.  I'll work later.


> Q. Is lib/complex.rb deprecated or not? If it is, *why* is it deprecated =
and not removed?

The main features of lib/complex.rb are embedded to core in 1.9,
but some features (e.g., Numeric#im and complex-sensitive Math)
are not.  Complex-sensitive Math (just CMath, not replacing core
Math) are moved to cmath.rb.  Numeric#im and replacing core Math
seemed to be deprecated.  So lib/complex.rb is now just for
compatibility.

This is just the fact.  I don't know its reason.


> Q. Is there a definitive document that explains the policy and behavior o=
f Math and Complex in 1.9?

Of course, no it isn't, I guess ;-(

--=20
Yusuke ENDOH <[e-mail]>