Created
December 5, 2022 18:15
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Kotlin sequence generator for stepping through float ranges without accumulating floating-point errors
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fun generateSequenceOfFractions( | |
range: ClosedFloatingPointRange<Float>, | |
step: Float | |
): Sequence<Float> { | |
val multiplier = 1f / step | |
val start = floor(range.start * multiplier).toInt() | |
val endInclusive = ceil(range.endInclusive * multiplier).toInt() | |
return generateSequence(start) { it + 1 } | |
.takeWhile { it <= endInclusive } | |
.map{ it.toFloat() / multiplier } | |
} |
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@RunWith(AndroidJUnit4::class) | |
class FractionsSequenceTest { | |
@Test | |
fun testGenerateSequenceOfFractions() { | |
val fractions = generateSequenceOfFractions(-1000f..1000f, step = 0.1f) | |
.toList() | |
fractions.forEach { | |
assertThat(it).isAtLeast(-1000f) | |
assertThat(it).isAtMost(1000f) | |
} | |
assertThat(fractions).isInStrictOrder() | |
assertThat(fractions).hasSize(1000 * 2 * 10 + 1) // Don't forget the 0 in the middle! | |
assertThat(fractions).contains(100f) | |
assertThat(fractions).contains(500.1f) | |
assertThat(fractions).contains(500.2f) | |
assertThat(fractions).contains(0.2f) | |
assertThat(fractions).contains(0f) | |
assertThat(fractions).contains(-10f) | |
assertThat(fractions).contains(-10f) | |
assertThat(fractions).contains(-10.3f) | |
assertThat(fractions).doesNotContain(-10.31f) | |
assertThat(fractions).doesNotContain(0.35f) | |
assertThat(fractions).doesNotContain(0.31f) | |
assertThat(fractions).doesNotContain(-.35f) | |
} | |
} |
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