mirror of https://github.com/DanilaFe/abacus
42 lines
1.8 KiB
Kotlin
42 lines
1.8 KiB
Kotlin
package org.nwapw.abacus.plugin.standard.operator
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import org.nwapw.abacus.context.PluginEvaluationContext
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import org.nwapw.abacus.function.OperatorAssociativity
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import org.nwapw.abacus.function.OperatorType
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import org.nwapw.abacus.function.interfaces.NumberOperator
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import org.nwapw.abacus.number.NumberInterface
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/**
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* The "N pick R" operator.
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*
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* his is a standard operator that returns the number of possible combinations
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* of a certain size can be taken out of a pool of a bigger size.
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*/
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class OperatorNpr: NumberOperator(OperatorAssociativity.RIGHT, OperatorType.BINARY_INFIX, 1) {
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override fun matchesParams(context: PluginEvaluationContext, params: Array<out NumberInterface>) =
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params.size == 2 && params[0].isInteger()
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&& params[1].isInteger()
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override fun applyInternal(context: PluginEvaluationContext, params: Array<out NumberInterface>): NumberInterface {
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val implementation = context.inheritedNumberImplementation
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if (params[0] < params[1] ||
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params[0].signum() < 0 ||
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params[0].signum() == 0 && params[1].signum() != 0)
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return implementation.instanceForString("0")
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var total = implementation.instanceForString("1")
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var multiplyBy = params[0]
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var remainingMultiplications = params[1]
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val halfway = params[0] / implementation.instanceForString("2")
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if (remainingMultiplications > halfway) {
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remainingMultiplications = params[0] - remainingMultiplications
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}
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while (remainingMultiplications.signum() > 0) {
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total *= multiplyBy
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remainingMultiplications -= implementation.instanceForString("1")
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multiplyBy -= implementation.instanceForString("1")
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}
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return total
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}
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} |