mirror of https://github.com/DanilaFe/abacus
37 lines
1.4 KiB
Kotlin
37 lines
1.4 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 factorial operator.
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*
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* This is a standard operator that simply evaluates the factorial of a number.
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*/
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class OperatorFactorial: NumberOperator(OperatorAssociativity.LEFT, OperatorType.UNARY_POSTFIX, 0) {
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override fun matchesParams(context: PluginEvaluationContext, params: Array<out NumberInterface>) =
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params.size == 1
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&& params[0].isInteger()
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&& params[0].signum() >= 0
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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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val one = implementation.instanceForString("1")
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if (params[0].signum() == 0) {
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return one
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}
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var factorial = params[0]
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var multiplier = params[0] - one
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//It is necessary to later prevent calls of factorial on anything but non-negative integers.
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while (multiplier.signum() == 1) {
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factorial *= multiplier
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multiplier -= one
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}
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return factorial
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}
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} |