[Aldor-l] Using GMP and extending the biging protocol

[pip88nl at gmail.com]

On Sat, Aug 16, 2008 at 12:02:33AM -0400, Stephen Watt wrote:
> The bigint macros are supposed to use the 2's complement overflows for
> the purposes of good, not evil :).
> 
> That is, there are places where they are supposed to happen and we
> count on the overflows wrapping around. This is used, for example, in
> testing for carries.   It allows us to use full word arithmetic from
> C.

Is this one of the places where it's supposed to overflow:

  /*
   * Allocate a new, stored integer value.
   */
  BInt
  xintStoreI(long n)
  {
          BInt    b;
          ULong   u;
          IInt    a;
  
          u = (n < 0) ? -n : n; // <-- here it overflows
          for (a = 1; ; a += 1, u >>= BINT_LG_RADIX)
                  if( u < BINT_RADIX ) break;
          b = bintAllocPlaces(a);
          return xintCopyInI(b, n);
  }

for LONG_MIN, nothing happens there. -n == n for LONG_MIN. Is this right?

Pippijn
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