Add BigDecimal implementation

This commit is contained in:
Alexander Nozik 2023-08-12 16:36:09 +03:00
parent efb853c1bc
commit 45eca71b3a
3 changed files with 116 additions and 1 deletions

View File

@ -0,0 +1,94 @@
/*
* Copyright 2018-2023 KMath contributors.
* Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
*/
package space.kscience.kmath.operations
import space.kscience.kmath.UnstableKMathAPI
import kotlin.math.abs
import kotlin.math.min
/**
* Decimal value with unfixed length
*
* The value is computed as `intValue*10^scale`.
*/
@UnstableKMathAPI
public data class BigDecimal(val intValue: BigInt, val scale: Int)
/**
* Convert current [BigInt] to a [BigDecimal] with scale 0.
*/
@UnstableKMathAPI
public fun BigInt.asDecimal(): BigDecimal = BigDecimal(this, 0)
/**
* A field for [BigDecimal] on top of [BigIntField]
*/
@UnstableKMathAPI
public object BigDecimalField : Field<BigDecimal> {
override val one: BigDecimal = BigIntField.one.asDecimal()
override val zero: BigDecimal = BigIntField.zero.asDecimal()
internal val ten: BigInt = BigIntField.number(10)
internal fun pow10(power: UInt): BigInt = ten.pow(power)
public fun Number.toDecimal(): BigDecimal = number(this)
/**
* Rescale a [BigDecimal] to have [targetScale]. If the target scale is larger than the current scale, loss of precision is possible.
*/
public fun BigDecimal.rescale(targetScale: Int): BigDecimal = if (targetScale == scale) {
this
} else {
val scaleDif = scale - targetScale
if (scaleDif > 0) {
BigDecimal(BigIntField.multiply(intValue, pow10(scaleDif.toUInt())), targetScale)
} else {
BigDecimal(BigIntField.divide(intValue, pow10(abs(scaleDif).toUInt())), targetScale)
}
}
public fun BigDecimal.pow10(power: Int): BigDecimal = BigDecimal(intValue, scale + power)
override fun add(left: BigDecimal, right: BigDecimal): BigDecimal = if (left.scale == right.scale) {
BigDecimal(BigIntField.add(left.intValue, right.intValue), left.scale)
} else {
val minScale = min(left.scale, right.scale)
//rescale both to a minimal scale
add(left.rescale(minScale), right.rescale(minScale))
}
override fun BigDecimal.unaryMinus(): BigDecimal = BigDecimal(-intValue, scale)
override fun scale(a: BigDecimal, value: Double): BigDecimal = with(BigIntField) {
BigDecimal(a.intValue * value, a.scale)
}
override fun divide(left: BigDecimal, right: BigDecimal): BigDecimal =
BigDecimal(BigIntField.divide(left.intValue, right.intValue), left.scale - right.scale)
override fun multiply(left: BigDecimal, right: BigDecimal): BigDecimal =
BigDecimal(BigIntField.multiply(left.intValue, right.intValue), left.scale + right.scale)
public operator fun Double.times(other: BigDecimal): BigDecimal = toDecimal() * other
public operator fun Double.div(other: BigDecimal): BigDecimal = toDecimal() / other
public operator fun Double.plus(other: BigDecimal): BigDecimal = toDecimal() + other
public operator fun Double.minus(other: BigDecimal): BigDecimal = toDecimal() - other
public operator fun BigDecimal.times(other: Double): BigDecimal = this * other.toDecimal()
public operator fun BigDecimal.div(other: Double): BigDecimal = this / other.toDecimal()
public operator fun BigDecimal.plus(other: Double): BigDecimal = this + other.toDecimal()
public operator fun BigDecimal.minus(other: Double): BigDecimal = this - other.toDecimal()
}

View File

@ -16,7 +16,6 @@ import kotlin.math.min
import kotlin.math.sign import kotlin.math.sign
private typealias Magnitude = UIntArray private typealias Magnitude = UIntArray
private typealias TBase = ULong
/** /**
* Kotlin Multiplatform implementation of Big Integer numbers (KBigInteger). * Kotlin Multiplatform implementation of Big Integer numbers (KBigInteger).
@ -215,6 +214,9 @@ public class BigInt internal constructor(
} }
} }
/**
* Convert this [BigInt] to a string using hexadecimal representation
*/
override fun toString(): String { override fun toString(): String {
if (this.sign == 0.toByte()) { if (this.sign == 0.toByte()) {
return "0x0" return "0x0"

View File

@ -0,0 +1,19 @@
/*
* Copyright 2018-2023 KMath contributors.
* Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
*/
package space.kscience.kmath.operations
import space.kscience.kmath.UnstableKMathAPI
import kotlin.test.Test
import kotlin.test.assertEquals
@OptIn(UnstableKMathAPI::class)
class BigDecimalTest {
@Test
fun simpleExpression() = with(BigDecimalField) {
assertEquals( 1000.0.toDecimal(),22.2.toDecimal().pow10(2) / 1.11)
}
}