3.20 Recursion

Usually the name of a definition is not visible in the definition; but earlier definitions are usually visible:

     1 0 / . \ "Floating-point unidentified fault" in Gforth on some platforms
     : / ( n1 n2 -- n )
       dup 0= if
         -10 throw \ report division by zero
       endif
       /           \ old version
     ;
     1 0 /

For recursive definitions you can use recursive (non-standard) or recurse:

     : fac1 ( n -- n! ) recursive
      dup 0> if
        dup 1- fac1 *
      else
        drop 1
      endif ;
     7 fac1 .
     
     : fac2 ( n -- n! )
      dup 0> if
        dup 1- recurse *
      else
        drop 1
      endif ;
     8 fac2 .

Assignment: Write a recursive definition for computing the nth Fibonacci number.

Reference (including indirect recursion): See Calls and returns.