60 lines
663 B
C++
60 lines
663 B
C++
// Subtract rational numbers
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//
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// Input: tos-2 minuend
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//
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// tos-1 subtrahend
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//
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// Output: difference on stack
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#include "stdafx.h"
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#include "defs.h"
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void
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qsub(void)
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{
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unsigned int *a, *ab, *b, *ba, *c;
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save();
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p2 = pop();
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p1 = pop();
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ab = mmul(p1->u.q.a, p2->u.q.b);
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ba = mmul(p1->u.q.b, p2->u.q.a);
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a = msub(ab, ba);
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mfree(ab);
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mfree(ba);
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// zero?
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if (MZERO(a)) {
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mfree(a);
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push(zero);
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restore();
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return;
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}
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b = mmul(p1->u.q.b, p2->u.q.b);
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c = mgcd(a, b);
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MSIGN(c) = MSIGN(b);
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p1 = alloc();
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p1->k = NUM;
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p1->u.q.a = mdiv(a, c);
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p1->u.q.b = mdiv(b, c);
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mfree(a);
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mfree(b);
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mfree(c);
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push(p1);
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restore();
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}
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