[perl #60674] sign($x) always returns 1 when $x ~~ Complex

[Moritz Lenz via RT]

On Wed Nov 19 07:35:48 2008, masak wrote:
> <masak> what should the behaviour of sign($x) be when $x is complex?

I'd argue that it's a Failure.
If you care about complex numbers, you usually want an angle instead,
which you can get with Complex.polar. (And it's easier to give it a
another meaning later that way)

(If you wanted a complex number with magnitude one, then you should call
that method "phase" or so, but that would confuse most people when
talking about real numbers.)

Cheers,
Moritz

> <masak> rakudo: say sign($_) for 42, -42, 0+42i
> <p6eval> rakudo 32877: OUTPUT[1␤-1␤1␤]
> <masak> somehow, that last one doesn't feel right to me.
> <masak> I vote for either an error or $x/abs($x)
> <PerlJam> why would it be an error?
> <masak> because 'sign' could be argued to only be applicable to real
> numbers.
> <masak> i.e. positive numbers, negative numbers, and zero.
> <PerlJam> but what is it specced to do?  :-)
> <masak> ah.
> <masak> it's supposed to return the 'sign' of a number.
> <masak> i.e. +1, -1 or 0 for the above three groups.
> <masak> in that way, it's a bit like <=>, except it always compares to
> 0
> <PerlJam> oh, it's wrong anyway I think.
> <PerlJam> rakudo: say sign(-5+3i);
> <p6eval> rakudo 32877: OUTPUT[1␤]
> <PerlJam> that can't be right.
> <masak> it always returns 1 on complex numbers.
> * masak reports a bug