Terrence Brannon wrote:
I [found](http://bit.ly/ar7uDi) a couple of naive fibonacci programs
by Bill Spight that work:
: FIB ?DUP
CASE
0 of 1 endof
1 of 1- RECURSE 1 endof
1- RECURSE TUCK +
ENDCASE ;
: FIB DUP 0= IF 1 ELSE 1- RECURSE TUCK + THEN ;
But I would like to know why mine does not work:
: fib { n -- fibn }
assert( n 0>= )
n CASE
0 OF 0 ENDOF
1 OF 1 ENDOF
2 OF 1 ENDOF
( otherwise ) n 1 - recurse n 2 - recurse +
ENDCASE ;
There is a non-explicit DROP before the ENDCASE. That's because the case
parameter has to disappear at some point. Change your code in this way:
> ( otherwise ) n 1 - recurse n 2 - recurse + SWAP
This way, the parameter will be dropped, not your computed Fib value,
and it will work.
In general, CASE is not a very useful or used construct in Forth; this
is not C. The less you use it, the better.
