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c038670114
It came about from a discussion in the bivector discord about programmatic testing for blade commutativity and why no texts talked about it. I came up with an idea that turned out not to work (I guess I'd overthought how count_flips works). In the end, I decided to keep it, and simplified metric's sign check.
31 lines
592 B
R
31 lines
592 B
R
#include "metric.h"
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#include "util.h"
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@implementation Metric
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+(Metric *)R:(int)p, int m, int z
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{
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Metric *metric = [[[Metric alloc] init] autorelease];
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metric.plus = ((1 << p) - 1) << z;
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metric.minus = ((1 << m) - 1) << (z + p);
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metric.zero = (1 << z) - 1;
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return metric;
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}
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static double
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count_minus (unsigned minus)
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{
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return count_bits (minus) & 1 ? -1 : 1;
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}
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-(double)apply:(unsigned) a, unsigned b
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{
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// find all the squared elements
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unsigned c = a & b;
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// any elements that square to 0 result in 0
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if (c & zero) {
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return 0;
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}
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return count_minus (c & minus);
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}
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@end
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