Continuation

Continuation objects are generated by Kernel#callcc. They hold a return address and execution context, allowing a nonlocal return to the end of the callcc block from anywhere within a program. Continuations are somewhat analogous to a structured version of C’s setjmp/longjmp (although they contain more state, so you might consider them closer to threads).

For instance:

   arr = [ "Freddie", "Herbie", "Ron", "Max", "Ringo" ]
   callcc{|$cc|}
   puts(message = arr.shift)
   $cc.call unless message =~ /Max/

produces:

   Freddie
   Herbie
   Ron
   Max

This (somewhat contrived) example allows the inner loop to abandon processing early:

   callcc {|cont|
     for i in 0..4
       print "\n#{i}: "
       for j in i*5...(i+1)*5
         cont.call() if j == 17
         printf "%3d", j
       end
     end
   }
   print "\n"

produces:

   0:   0  1  2  3  4
   1:   5  6  7  8  9
   2:  10 11 12 13 14
   3:  15 16