59 lines
1.7 KiB
C
59 lines
1.7 KiB
C
// Filename: nearly_zero.h
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// Created by: drose (08Mar00)
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//
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////////////////////////////////////////////////////////////////////
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#ifndef NEARLY_ZERO_H
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#define NEARLY_ZERO_H
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// The following two functions are defined just to make the
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// NEARLY_ZERO() macro work. They each return a suitable nearly-zero
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// value for their corresponding numeric type.
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INLINE double
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get_nearly_zero_value(double) {
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return 1.0e-12;
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}
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INLINE float
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get_nearly_zero_value(float) {
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return 1.0e-6f;
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}
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// IS_THRESHOLD_ZERO(value, threshold) returns true if the value is
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// within threshold of zero.
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#define IS_THRESHOLD_ZERO(value, threshold) \
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((value) < (threshold) && (value) > -(threshold))
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// IS_THRESHOLD_EQUAL(value1, value2, threshold) returns true if the
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// two values are within threshold of each other.
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#define IS_THRESHOLD_EQUAL(value1, value2, threshold) \
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(IS_THRESHOLD_ZERO((value1) - (value2), threshold))
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// NEARLY_ZERO(float) returns a number that is considered to be so
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// close to zero as not to matter for a float. NEARLY_ZERO(double)
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// returns a similar, smaller number for a double.
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#define NEARLY_ZERO(NumType) (get_nearly_zero_value((NumType)0))
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// IS_NEARLY_ZERO(value) returns true if the value is very close to
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// zero.
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#define IS_NEARLY_ZERO(value) \
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(IS_THRESHOLD_ZERO(value, get_nearly_zero_value(value)))
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// IS_NEARLY_EQUAL(value1, value2) returns true if the two values are
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// very close to each other.
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#define IS_NEARLY_EQUAL(value1, value2) \
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IS_NEARLY_ZERO((value1) - (value2))
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// MAYBE_ZERO(value) returns 0 if the value is nearly zero, and the
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// value itself otherwise.
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#define MAYBE_ZERO(value) \
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(IS_NEARLY_ZERO(value) ? 0.0 : value)
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#endif
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