P48 - Truth tables for logical expressions (3).

> true.xor_(true, false, true)
true

kotlin

package org.kotlin99.logic

import com.natpryce.hamkrest.assertion.assertThat
import com.natpryce.hamkrest.equalTo
import org.junit.Test

// Functions below cannot be "inline" because there are recursive.

fun Boolean.and_(vararg others: Boolean): Boolean =
    if (others.isEmpty()) this else this.and_(others.first()).and_(*others.tail())

fun Boolean.or_(vararg others: Boolean): Boolean =
    if (others.isEmpty()) this else this.or_(others.first()).or_(*others.tail())

fun Boolean.xor_(vararg others: Boolean): Boolean =
    if (others.isEmpty()) this else this.xor_(others.first()).xor_(*others.tail())

private fun BooleanArray.tail() = drop(1).toBooleanArray()


class P48Test {
    @Test fun `logical expressions`() {
        assertThat(true.and_(true, false, true), equalTo(false))
        assertThat(true.or_(true, false, false), equalTo(true))
        assertThat(true.xor_(true, false, true), equalTo(true))
    }
}