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21 lines
327 B
C
21 lines
327 B
C
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#include <limits.h>
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#include "libm.h"
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/*
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special cases:
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logb(+-0) = -inf
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logb(+-inf) = +inf
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logb(nan) = nan
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these are calculated at runtime to raise fp exceptions
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*/
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double logb(double x) {
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int i = ilogb(x);
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if (i == FP_ILOGB0)
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return -1.0/fabs(x);
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if (i == FP_ILOGBNAN || i == INT_MAX)
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return x * x;
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return i;
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}
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