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support transitive principle in nearly_equal

This commit is contained in:
David Rose 2002-06-05 19:41:13 +00:00
parent 2acf89afeb
commit 6d9042b006
1 changed files with 11 additions and 4 deletions
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15
panda/src/linmath/nearly_zero.h
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@ -40,9 +40,16 @@ get_nearly_zero_value(float) {
((value) < (threshold) && (value) > -(threshold))
// IS_THRESHOLD_EQUAL(value1, value2, threshold) returns true if the
// two values are within threshold of each other.
// two values are within threshold of each other. The transitive
// principle is guaranteed: IS_THRESHOLD_EQUAL(a, b, t) &&
// IS_THRESHOLD_EQUAL(b, c, t) implies IS_THRESHOLD_EQUAL(a, c, t).
// We could define this via IS_THRESHOLD_ZERO(a - b, t) that wouldn't
// guarantee the transitive principle, stated above. So we need a
// more complex definition that rounds these to the nearest multiples
// of threshold before comparing them.
#define IS_THRESHOLD_EQUAL(value1, value2, threshold) \
(IS_THRESHOLD_ZERO((value1) - (value2), threshold))
(cfloor(value1 / threshold + 0.5f) == cfloor(value2 / threshold + 0.5f))
// NEARLY_ZERO(float) returns a number that is considered to be so
@ -58,13 +65,13 @@ get_nearly_zero_value(float) {
// IS_NEARLY_EQUAL(value1, value2) returns true if the two values are
// very close to each other.
#define IS_NEARLY_EQUAL(value1, value2) \
IS_NEARLY_ZERO((value1) - (value2))
(IS_THRESHOLD_EQUAL(value1, value2, get_nearly_zero_value(value1)))
// MAYBE_ZERO(value) returns 0 if the value is nearly zero, and the
// value itself otherwise.
#define MAYBE_ZERO(value) \
(IS_NEARLY_ZERO(value) ? 0.0 : value)
(IS_NEARLY_ZERO(value) ? 0.0 : (value))
#endif