53 lines
792 B
C
53 lines
792 B
C
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#include "os.h"
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#include <mp.h>
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#include "dat.h"
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// diff = abs(b1) - abs(b2), i.e., subtract the magnitudes
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void
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mpmagsub(mpint *b1, mpint *b2, mpint *diff)
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{
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int n, m, sign;
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mpint *t;
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// get the sizes right
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if(mpmagcmp(b1, b2) < 0){
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sign = -1;
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t = b1;
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b1 = b2;
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b2 = t;
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} else
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sign = 1;
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n = b1->top;
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m = b2->top;
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if(m == 0){
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mpassign(b1, diff);
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diff->sign = sign;
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return;
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}
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mpbits(diff, n*Dbits);
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mpvecsub(b1->p, n, b2->p, m, diff->p);
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diff->sign = sign;
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diff->top = n;
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mpnorm(diff);
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}
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// diff = b1 - b2
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void
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mpsub(mpint *b1, mpint *b2, mpint *diff)
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{
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int sign;
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if(b1->sign != b2->sign){
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sign = b1->sign;
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mpmagadd(b1, b2, diff);
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diff->sign = sign;
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return;
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}
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sign = b1->sign;
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mpmagsub(b1, b2, diff);
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if(diff->top != 0)
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diff->sign *= sign;
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}
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