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Re: GMP code committed -- watch for bugs.

From: Mikael Djurfeldt
Subject: Re: GMP code committed -- watch for bugs.
Date: Sun, 06 Apr 2003 11:23:01 +0200
User-agent: Gnus/5.090016 (Oort Gnus v0.16) Emacs/21.2 (gnu/linux)

Rob Browning <address@hidden> writes:

> (Mikael: if you get a second, could you look at random.c and make sure
>  you don't see any obvious mistakes.  One thing in particular -- could
>  you look at the FIXME there -- if there's a chance that a random
>  bignum could end up with enough leading zeroes to place it in fixnum
>  territory, then we need to return scm_i_normbig (result), but I
>  wanted to check with you first.  Returning a bignum with a value in
>  fixnum range would violate an assumption made by other guile
>  numerical code.)

Yes, we certainly must normalize.  The old code looked like this:

      /* now fill up the rest of the bignum */
      while (i)
        bits[--i] = scm_the_rng.random_bits (state);
      /* use scm_i_normbig to cut away leading zeros and/or convert to inum */
      b = scm_i_normbig (b);
      if (SCM_INUMP (b))
        return b;

Best regards,

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