Continuing the next iteration

Ruby
1

What’s the Ruby equivalent of “next” in Perl or “continue” in C?
Is it possible to continue an outer loop, as in Perl’s “next”
with a label argument?

2

YAD wrote:

What’s the Ruby equivalent of “next” in Perl or “continue” in C?
Is it possible to continue an outer loop, as in Perl’s “next”
with a label argument?

You may or may not have heard this, but jumping to a label is frowned
upon
in reliable, maintainable code. I don’t find anything like “next” in
Ruby,
but there is a “Continuation” class that can jump out of a complex
nested
structure.

http://www.rubycentral.com/book/ref_c_continuation.html

3

YAD wrote:

callcc do |nextRow|

I wonder how much overhead there is associated with this
compared to the row.unique.size approach…

4

Paul L. wrote:

You may or may not have heard this, but jumping to a label is frowned upon
There’s nothing wrong with a structured jump without a label.

btw, next is listed in the manual along with break, redo, and retry.

but there is a “Continuation” class that can jump out of a complex nested
structure.
http://www.rubycentral.com/book/ref_c_continuation.html

Well, it’s a little on the clunky side, but it works.

def doRows (grid,char)
(0…3).each do |row|
callcc do |nextRow|
(0…3).each do |col|
nextRow.call() if grid[row][col] != char
end
return true
end
end
return false
end

Thanks for the help, I would have had a hard time finding that
on my own.

5

On 9/7/06, YAD [email protected] wrote:

What’s the Ruby equivalent of “next” in Perl or “continue” in C?
Is it possible to continue an outer loop, as in Perl’s “next”
with a label argument?

–
Yet another Dan

Try catch/throw, although if you can rework your code into smaller
chunks and use a return it is often more readable.

catch (:deep_error) do
(0…10).each do |i|
puts i
(0…10).each do |j|
puts j
throw :deep_error if 2 == j
end
end
end
puts “done”

6

YAD wrote:

Well, it’s a little on the clunky side, but it works.
return false
end

def do_rows(grid, char)
grid.each {|row|
return true if row.all?{|c| c==char}
}
return nil
end

7

On 9/8/06, Patrick H. [email protected] wrote:

Try catch/throw, although if you can rework your code into smaller
end
puts “done”

Sorry I did not read as closely as I should – my example was just of
a “break,” if you are after next/continue functionality, you need to
put the catch/throw inside the outer loop:

(0…10).each do |i|
puts i
catch :deep_error do
(0…10).each do |j|
puts j
(0…10).each do |k|
puts k
throw :deep_error if 2 == k
end
end
puts “never going to happen”
end
end

8

William J. wrote:

def do_rows(grid, char)
grid.each {|row|
return true if row.all?{|c| c==char}
}
return nil
end

Yes, that’s the way to do it. Columns are still an issue,
but that looks like the most natural solution. Thanks.

9

YAD wrote:

YAD wrote:

callcc do |nextRow|

I wonder how much overhead there is associated with this
compared to the row.unique.size approach…

Amen. If you have extra data in the data set, I’d personally just first
create a clean data set to process without jumps. And get rid of nested
loops. And indulge in a lot more anal code cleanliness.

David V.