RECURSE   

RECURSE ( ---)

Append the execution semantics of the current definition to the current definition.

The usual example is the coding of the factorial function:

: FACTORIAL ( +n1 -- +n2)
   DUP 2 < IF DROP 1 EXIT THEN
   DUP 1- RECURSE *
;

Specific Flash Forth

n2 = n1(n1-1)(n1-2)...(2)(1), the product of n1 with all positive integers less than itself (as a special case, zero factorial equals one). While beloved of computer scientists, recursion makes unusually heavy use of both stacks and should therefore be used with caution.

: test01 ( n ---)
    dup 1- dup
    0 > if
        test01
    then 
    .
  ;