mirror of
https://github.com/wren-lang/wren.git
synced 2026-01-14 07:38:03 +01:00
a8ea2a91a6
The methods Sequence.map and Sequence.where are now implemented using deferred execution. They return an instance of a new Sequence-derived class that performs the operation while iterating. This has three main advantages: * It can be computationally cheaper when not the whole sequence is iterated. * It consumes less memory since it does not store the result in a newly allocated list. * They can work on infinite sequences. Some disadvantages are: * Iterating the returned iterator will be slightly slower due to the added indirection. * You should be aware that modifications made to the original sequence will affect the returned sequence. * If you need the result in a list, you now need to call Sequence.list on the result.
47 lines
1.1 KiB
Plaintext
47 lines
1.1 KiB
Plaintext
// Infinite iterator demonstrating that Sequence.map is not eager
|
|
class FibIterator {
|
|
new {
|
|
_current = 0
|
|
_next = 1
|
|
}
|
|
|
|
iterate {
|
|
var sum = _current + _next
|
|
_current = _next
|
|
_next = sum
|
|
}
|
|
|
|
value { _current }
|
|
}
|
|
|
|
class Fib is Sequence {
|
|
iterate(iterator) {
|
|
if (iterator == null) return new FibIterator
|
|
iterator.iterate
|
|
return iterator
|
|
}
|
|
|
|
iteratorValue(iterator) { iterator.value }
|
|
}
|
|
|
|
var squareFib = (new Fib).map {|fib| fib * fib }
|
|
var iterator = null
|
|
|
|
IO.print(squareFib is Sequence) // expect: true
|
|
IO.print(squareFib) // expect: instance of MapSequence
|
|
|
|
iterator = squareFib.iterate(iterator)
|
|
IO.print(squareFib.iteratorValue(iterator)) // expect: 0
|
|
|
|
iterator = squareFib.iterate(iterator)
|
|
IO.print(squareFib.iteratorValue(iterator)) // expect: 1
|
|
|
|
iterator = squareFib.iterate(iterator)
|
|
IO.print(squareFib.iteratorValue(iterator)) // expect: 1
|
|
|
|
iterator = squareFib.iterate(iterator)
|
|
IO.print(squareFib.iteratorValue(iterator)) // expect: 4
|
|
|
|
iterator = squareFib.iterate(iterator)
|
|
IO.print(squareFib.iteratorValue(iterator)) // expect: 9
|