kotlin-stdlib/kotlin.collections/DoubleIterator

DoubleIterator

abstract class DoubleIterator : Iterator<Double> (source)

An iterator over a sequence of values of type Double.

This is a substitute for Iterator<Double> that provides a specialized version of next(): T method: nextDouble(): Double and has a special handling by the compiler to avoid platform-specific boxing conversions as a performance optimization.

In the following example:

class DoubleContainer(private val data: DoubleArray) {

    // DoubleIterator instead of Iterator<Double> in the signature
    operator fun iterator(): DoubleIterator = object : DoubleIterator() {
        private var idx = 0

        override fun nextDouble(): Double {
            if (!hasNext()) throw NoSuchElementException()
            return data[idx++]
        }

        override fun hasNext(): Boolean = idx < data.size
    }
}

for (element in DoubleContainer(doubleArrayOf(1.0, 2.0, 3.0))) {
    ... handle element ...
}
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No boxing conversion is performed during the for-loop iteration. Note that the iterator itself will still be allocated.

Since Kotlin

1.0

Constructors

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constructor()

Functions

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fun <T> Iterator<T>.asSequence(): Sequence<T>

Creates a sequence that returns all elements from this iterator. The sequence is constrained to be iterated only once.

Since Kotlin 1.0
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inline fun <T> Iterator<T>.forEach(operation: (T) -> Unit)

Performs the given operation on each element of this Iterator.

Since Kotlin 1.0
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expect abstract operator fun hasNext(): Boolean

Returns true if the iteration has more elements.

Since Kotlin 1.0
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inline operator fun <T> Iterator<T>.iterator(): Iterator<T>

Returns the given iterator itself. This allows to use an instance of iterator in a for loop.

Since Kotlin 1.0
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operator override fun next(): Double

Returns the next element in the iteration.

Since Kotlin 1.0
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abstract fun nextDouble(): Double

Returns the next element in the iteration without boxing conversion.

Since Kotlin 1.0
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fun <T> Iterator<T>.withIndex(): Iterator<IndexedValue<T>>

Returns an Iterator that wraps each element produced by the original iterator into an IndexedValue containing the index of that element and the element itself.

Since Kotlin 1.0