Re: [Chicken-users] most-{positive,negative}-fixnum

[Alejandro Forero Cuervo]

> I need to determine the most positive and most negative fixnums,
> given that Chicken has both 32-bit and 64-bit builds.  Can these
> be added as constants, or is there some easy way to compute them?

I used the following:

  (use format)

  (define (find type)
    (let loop ((i type) (mult 2))
      (format (current-error-port) "Try: ~A (~A)~%" i mult)
      (cond
        ((fixnum? (round (+ type (* i mult)))) (loop (round (+ type (* i 
mult))) mult))
        ((> mult 1.0000000000001) (loop i (/ (+ mult 1) 2)))
        ((fixnum? (+ type i)) (loop (+ type i) mult))
        (else i))))

  (format (current-error-port) "Range: ~A to ~A~%" (find -1) (find 1))

In my build this gives:

Range: -1073741824 to 1073741823

Note, however, that you can use doubles to represent greater numbers
without losing precision (since, AFAIR, doubles can use more bits for
their non-decimal part than integers/fixnums can).

Alejo.
http://azul.freaks-unidos.net/