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Recursion Error
Posted: Thu Nov 16, 2006 5:50 pm
by Grundle
I am working with the latest newlisp-TK on a windows platform. I have written the following simple recursive algorithm for the fibonacci sequence
Code: Select all
(define (fib 'val)
(if (< val 2)
1
(+ (fib (- val 1)) (fib (- val 2)))))
What is strange is that when I try to do either of the following statements
It will always return 1. I have run the algorithm through the debugger supplied, and I have been able to determine that it is saying that all values are less than 2, which results in an automatic return of 1. Why would it be doing this?
Posted: Thu Nov 16, 2006 6:08 pm
by Grundle
Ahh, way to go n00ber. I just figured out why this is happening. Note the difference in the following statements
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(define (fib val) .... )
(define (fib 'val) ... )
The first define is of course correct. The second will cause this behavior, because I believe that it is setting a variable at that point in stead of allowing a variable to be passed in.
Such a silly mistake :D Please laugh accordingly ;)
Posted: Thu Nov 16, 2006 6:37 pm
by Lutz
This is what is happening:
'val' is passed as a symbol and therefor cannot binf to the number passed. The contents of 'val' beeing 'nil' in (< val 2) results in the comparison (< nil 2), which is 'true'. The compare operators when given operands of different types compare type values as of the following order:
Atoms: nil, true, integer or float, string, symbol, primitive
Lists: quoted list/expression, list/expression, lambda, lambda-macro
Lutz
ps:
http://newlisp.org/newlisp_manual.html#logical