[OpenBIOS] Kickstarting a revolution ...

[Stefan Reinauer]

* Mads Martin Jørgensen <mmj at suse.de> [011219 12:50]:
> * Stefan Reinauer <stepan at openbios.net> [Dec 19. 2001 01:56]:
> > -- 
> > Ok : FC RECURSE DUP 1 > IF DUP 1 - FC * ELSE DROP 1 ENDIF ; 42 FC .
> 
> :-) Maybe our project founder would elaborate on that one? Not all of us
> speak Forth that good (yet :)

:-) Actually it should have been a little forth word definition that
calculates faculty of the given number recursively. But there were 2 mistakes
in it.
The correct version would be:
	Ok : fc recursive dup 1 > if dup 1 - fc * then ; 42 fc .
(with Ok being the Open Firmware prompt)

The program can be written in a more readable way: 

: FC RECURSIVE ( n -- n! | 1 )	\ This is the word definition including
				\ the stack diagram.
  DUP 1 >			\ safe n and compare it to 1
  IF				\ if (n>1)
    DUP 1 - FC *		\ fc(n) = fc(n-1) * n
  ELSE
    DROP 1			\ If n=1 or below (n! not defined for n<1)
				\ bail out of recursion.
  THEN
;

"42 fc ." then pushes 42 to the stack, calculates faculty and prints it.

Best regards,
  Stefan Reinauer

-- 
Ok : fc recursive dup 1 > if dup 1 - fc * then ; 42 fc .
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