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Gforth Manual

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 most 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 section 5.8.5 Calls and returns.