how to do a next in a elisp dotimes loop

Question

By next I mean next as found in ruby/perl/python/etc

#!/usr/bin/ruby

for i in 0..5
   if i < 2 then
      next
   end
   puts "Value of local variable is #{i}"
end

Answer 1

There is no such facility for loops. Considering next in Ruby is the idiom to avoid a nested if, you can easily work around this by using this advice the other way around.

(dotimes (i 6)
  (unless (< i 2)
    (message "Value of local variable is %d" i)))

An even uglier workaround is using the throw/catch facility (which is designed for control flow, not exception handling):

(dotimes (i 6)
  (catch 'next
    (when (< i 2)
      (throw 'next t))
    (message "Value of local variable is %d" i)))

I'd recommend rethinking the problem so that you don't need next at all. Or use a more powerful looping construct, such as cl-loop.

Answer 2

The next statement is just a jump to the end of the loop. Emacs Lisp doesn't have one but it does have "goto":

(dotimes (i 5)
  (cl-tagbody
   (when (< i 2)
     (go next))
   (message "Value of i is %d." i)
   next))

(Here next is just an arbitrary label, specifying a target for the jump.)

I don't actually recommend this style. Prbably rephrasing your loop to avoid next is better.

Answer 3

Using cl-loop:

(cl-loop for i from 0 to 5
         unless (< i 2)
         do (message "Value of local variable is %d" i))