From: Benjamin Oakes <benjamin.d.oakes@...>
Date: 2008-03-11T20:18:12+09:00
Subject: Re: newbie question

On Mon, Mar 10, 2008 at 9:11 AM, Frantisek Psotka
<frantisek.psotka@matfyz.cz> wrote:
> yes, i can write
>
>  a = b || a
>
>  but isn't it more complex. imagine that b is nil. then a = a will be
>  evaluated?
>
>  maybe time for feature request? new operator a =|| (a = b if b)
>
>  (variable = params[:nice_symbol] if params[:nice_symbol] doesnt look
>  very nice)
>
>
>
>
>  Lars wrote:
>  > On Mar 10, 11:50 am, Farrel Lifson <farrel.lif...@gmail.com> wrote:
>  >> On 10/03/2008, Frantisek Psotka <frantisek.pso...@matfyz.cz> wrote:
>  >>
>  >> > is in ruby operator for:
>  >>
>  >> >  a = b if b
>  >>
>  >> >  a (operator) b
>  >>
>  >> a ||= b
>  >
>  > "a ||= b" means "a = b unless a".
>  >
>  > I don't think there is an operator for "a = b if b".
>  >
>  > Luckily, "a = b if b" is valid ruby code. "a = b || a" or "a = (b or
>  > a)" would also work.
>
>
>
> --
>  Posted via http://www.ruby-forum.com/.
>
>

I guess I don't understand what the point of having a = b if b is.
The only thing I can see that's different than a ||= b is that false
will become nil.  Here's what I tried:

def demo(some_value)
  out = some_value if some_value
  puts("out: #{out.inspect}")
  out = nil || some_value
  puts("out: #{out.inspect}")
  out = some_value
  puts("out: #{out.inspect}")
  a_different_variable ||= some_value
  puts("a_different_variable: #{a_different_variable.inspect}")
  puts('------------')
end

demo(nil)
demo(88)
demo(false)

Outputs:

out: nil
out: nil
out: nil
a_different_variable: nil
------------
out: 88
out: 88
out: 88
a_different_variable: 88
------------
out: nil
out: false
out: false
a_different_variable: false
------------

So... Why doesn't ||= work for how you're using it?  (Why do you want
the "b if b" behavior?)

-- Ben (aka divokz)