call-with-current-continuation
call/cc

    (call/cc) A Lisp control function that
   implements the continuation passing style of programming.

   In continuation passing style (CPS), every function f takes an
   extra final argument k called the "continuation".  The
   continuation is itself a function and represents the rest of the
   program.  Instead of just returning a value in the normal way, f
   passes it as an argument to k and returns the result of that.

   call/cc takes a function f as its argument and calls f, passing it
   the current continuation k.  It thus allows a CPS function to be
   called in a non-CPS (direct) context.

   For example, if the final result is to print the value returned by
   call/cc then anything passed to k will also be printed.

   E.g, in Scheme:

    (define (f k)
   	 (k 1)
   	 (k 2)
   	 3)

    (display (call-with-current-continuation f))

   Will display 1.

   [Is this correct?]

   (2014-09-24)