From: Nikodemus Siivola <tsiivola@...>
Date: 2002-07-09T20:13:45+09:00
Subject: Re: for ... else ... end


On Tue, 9 Jul 2002, Yukihiro Matsumoto wrote:

> But I don't feel "for .. else" is intuitive.  The "else" seem like
> indentation mistake rather than loop termination hook.  Maybe there
> can be a more suitable keyword.

Why not :

"iterator ... then ... else ... end"

while cond {
  # stuff
} then {
  # more stuff after succ. iteration
} else {
  # handle failed iteration
}

collection.each do |item|
  # handle item
then |collection|
  # handle collection after succ. iteration
else |collection|
  # handle collection after failed iteration
end

But then again, I get the feeling that instead of extending syntax for this
specific case there should be a way of defining your own control structures
by chaining blocks: (I believe SmallTalk has something like this?)

def iter &all then &ok else &err
  ok = true
  for x in @array
    yield(x) &all || { yield(self) &err; ok = false; break }
  end
  yield(self) &ok if ok
end

collection.iter { |x|
  break unless x.test
} then { |all|
  all.stamp
} else { |all|
  all.dump
}

 -- Nikodemus