ref: dac5756766be04f303bceaea49eba4f6ffc4e25e
dir: /sys/src/libmp/port/mpsub.c/
#include "os.h" #include <mp.h> #include "dat.h" // diff = abs(b1) - abs(b2), i.e., subtract the magnitudes void mpmagsub(mpint *b1, mpint *b2, mpint *diff) { int n, m, sign; mpint *t; // get the sizes right if(mpmagcmp(b1, b2) < 0){ assert(((b1->flags | b2->flags | diff->flags) & MPtimesafe) == 0); sign = -1; t = b1; b1 = b2; b2 = t; } else { diff->flags |= (b1->flags | b2->flags) & MPtimesafe; sign = 1; } n = b1->top; m = b2->top; if(m == 0){ mpassign(b1, diff); diff->sign = sign; return; } mpbits(diff, n*Dbits); mpvecsub(b1->p, n, b2->p, m, diff->p); diff->sign = sign; diff->top = n; mpnorm(diff); } // diff = b1 - b2 void mpsub(mpint *b1, mpint *b2, mpint *diff) { int sign; if(b1->sign != b2->sign){ assert(((b1->flags | b2->flags | diff->flags) & MPtimesafe) == 0); sign = b1->sign; mpmagadd(b1, b2, diff); diff->sign = sign; return; } sign = b1->sign; mpmagsub(b1, b2, diff); if(diff->top != 0) diff->sign *= sign; }