Intercepting break within a block after yield

[Alexey Verkhovsky]

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Sorry for posting this without a subject earlier.

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Posted: Tue, 14 Sep 2004 21:51:07 +0300
From: Alexey Verkhovsky <[email protected]>
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A question from Ruby-Forum:
http://www.ruby-forum.org/bb/viewtopic.php?t=13

If I do this:

Code:

a = [1, 2, 3]
a.each do |x|
puts x
if x == 2 then break; end
end

It works (prints 1, 2 then stops), but returns nil. Normally a.each
should return a.

I need an iterator that will return all elements processed until the
break. E.g.

Code:

class Array
def each_with_a_twist
self.each_with_index do
|element, index|
yield elementbreak self[0, index]
end
end
end

Is it possible?

I've come up with the following suggestion:

class A
def a
yield
ensure puts "after block"; return 1
end
end

I can see that this code is not good enough, because it doesn't
differentiate between the block terminated by break and the block
terminated by an error. What would be the Ruby Way here?

Alex





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[Jamis Buck]

Sorry for posting this without a subject earlier.


------------------------------------------------------------------------

Subject:
No Subject
From:
Alexey Verkhovsky <[email protected]>
Date:
Thu, 16 Sep 2004 03:50:06 +0900
To:
(e-mail address removed) (ruby-talk ML)

To:
(e-mail address removed) (ruby-talk ML)


A question from Ruby-Forum:
http://www.ruby-forum.org/bb/viewtopic.php?t=13

If I do this:

Code:

a = [1, 2, 3]
a.each do |x|
puts x
if x == 2 then break; end
end

It works (prints 1, 2 then stops), but returns nil. Normally a.each
should return a.

I need an iterator that will return all elements processed until the
break. E.g.

Code:

class Array
def each_with_a_twist
self.each_with_index do
|element, index|
yield element

INTERCEPT THE BREAK <<<

break self[0, index]
end
end
end

Is it possible?

I've come up with the following suggestion:

class A
def a
yield
ensure puts "after block"; return 1
end
end

I can see that this code is not good enough, because it doesn't
differentiate between the block terminated by break and the block
terminated by an error. What would be the Ruby Way here?

Alex

Would something like this work?

class Array
def each_with_a_twist
index = 0
return_list = true
self.each_with_index do |element, index|
yield element
end
rescue Exception
return_list = false
raise
ensure
return_list and return self[0..index]
end
end

a = [ 1, 2, 3, 4, 5 ]
result = a.each_with_a_twist { |i| break "blah" if i > 2 }
p result

result = a.each_with_a_twist { |i| raise "blah" if i > 2 }
p result

--
Jamis Buck
(e-mail address removed)
http://www.jamisbuck.org/jamis

"I use octal until I get to 8, and then I switch to decimal."