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lispread-eval-print-loopclisp

CLISP overflow after multiplication

i'm trying to get a first lisp program to work using the CLISP implementation, by typing

(print (mod (+ (* 28433 (expt 2 7830457) 1)) (expt 10 10))))

in the REPL.

but it gives me *** - overflow during multiplication of large numbers. i thought lisp features arbitrary size/precision. how could that ever happen then?

Solution

  • According to http://clisp.cons.org/impnotes/num-concepts.html the maximum size for a bignum is (2^2097088 - 1) and your 2^7830457 is much larger than that.

    Perhaps you can look at breaking down that number - perhaps separate out a number of smaller 2^X factors...