From: Brian Candler <B.Candler@...>
Date: 2004-09-29T18:18:28+09:00
Subject: Re: DRY ruby idiom

>      I will not that (in the original poster's terms), this is
>    
>           var = val || var

or
   a = foo.value || a

which more clearly shows the value (!) of this construct. Smart.

Thinking about my own code, I tend to write

  var = val unless val.nil?

which is even more verbose, but seems a bit clearer, and works for the case
where val=false. However I end up assigning to a temporary variable 'val' in
the case of a complex expression. Maybe I'll adopt your pattern instead,
although I think it would leave some people scratching their heads at first.

There is the more general case of

    if some.complex.expression
      ... do something with some.complex.expression
    end

which I typically write as

    if (val = some.complex.expression)
       ... do something with val
    end

This does suggest some other solutions:

    a = tmp if tmp = foo.value      ## fails - first tmp is treated as method
    if tmp = foo.value; a = tmp; end
    (tmp = foo.value) && (a = tmp)

Icky though. It might be nice if the value of the condition evaluated in an
'if', or the LHS of && or ?:, were somehow available to the body/RHS. I
can't think how it would work nicely:

    foo.value && a = $#    #yuk

Regards,

Brian.