From: David Alan Black <dblack@...>
Date: 2002-07-10T02:36:18+09:00
Subject: Re: for ... else ... end

Hi --

On Wed, 10 Jul 2002, Austin Ziegler wrote:

> On Wed, 10 Jul 2002 01:52:38 +0900, David Alan Black wrote:
> > I still don't see how a code block can have an 'else' clause.
> > Wouldn't this make for some awfully bizarre code?

[...]

> > array.each {|e| else puts "Empty array"}
>
> > Given an empty array, this else clause would execute. [...] And,
> > come to think of it.... shouldn't the block not be entered at all
> > if the array is empty? What the "else" thing means is that the
> > block *will* be entered. I wish I knew the technical term for why
> > that isn't OK :-) but doesn't it feel very non-OK?
>
> Agreed. I'd prefer to do that as:
>
> puts "Empty array" if array.empty?
> array.each { |e| puts e } unless array.empty?
>
> It might be nice to have some syntactic sugar that does something
> like that:
>
> array.each { |e| puts e } unless array.empty then puts "Empty array"

Hmmm... unless I'm missing something, this can be done very simply:

  if array.empty?
    puts "Empty array"
  else
    array.each {|e| puts e}
  end

or even:

  puts "Empty array" if array.each {|e| puts e}.empty?

since Array#each returns the original array.  (But that has a slightly
inside-out feel to it.)

(Of course if it's really just #puts, then:

  puts if array.empty? then "Empty array" else array end

(or ternary operator equivalent, as I think Det pointed out)

but that can't be generalized :-)

> FWIW, this was someone else's example that I adapted from a
> for...end format to an each do...end format -- because I don't think
> that it's necessarily a good way of doing it.

Sorry if I was attributing too much to you... it was actually hard to
find exactly the right point of entry into the thread!


David

-- 
David Alan Black
home: dblack@candle.superlink.net
work: blackdav@shu.edu
Web:  http://pirate.shu.edu/~blackdav