README
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ranges
Composable combinators over Go 1.23 iter.Seq[T] range-over-func iterators: Values, Empty, Filter/FilterPointer, Map, Join, Limit, Unique, and Slice. Part of rosetta.
This is the modern iteration toolkit (built on iter.Seq); for the older cursor-style Next(any) bool interface, see iterator.
What matters here
- Every combinator propagates early termination via the
yieldreturn value. Each wraps the source sequence and returns from its ownyieldloop when the downstreamyieldreturnsfalse. This is what makesfor x := range ranges.Limit(10, seq)stop the source after 10 items instead of draining it —breakin the consumer must reach the producer. The tests assert this (*_EarlyTermination); a combinator that ignoresyield's bool would silently break it. iter.Seqvalues are lazy and re-runnable. Ranging the same sequence twice re-executes it from the start; combinators build a pipeline that does no work until ranged. Don't assume single-shot semantics.FilterPointerpasses*Tto its predicate (to avoid copying large elements), whileFilterpassesTby value. PickFilterPointerfor big structs; the predicate must not retain the pointer past the call.Sliceis the terminal that materializes a sequence into[]T— use it when you need a concrete slice; otherwise keep things lazy.
Documentation
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Overview ¶
Package ranges provides combinators for iter.Seq iterators: Filter, Map, Limit, Join, Unique, Empty, and Values, plus Slice to collect one.
Everything here is lazy. Each combinator returns a new iter.Seq that pulls from its source only as the consumer ranges over it, so chaining them composes a single pass rather than building intermediate slices, and stopping early stops the whole chain.
This is the modern counterpart to the iterator package, which adapts the older cursor-style interface. New code should start here.
Index ¶
- func Empty[T any]() iter.Seq[T]
- func Filter[T any](iterator iter.Seq[T], predicate func(T) bool) iter.Seq[T]
- func FilterPointer[T any](iterator iter.Seq[T], predicate func(*T) bool) iter.Seq[T]
- func Join[T any](iterators ...iter.Seq[T]) iter.Seq[T]
- func Limit[T any](max int, iterator iter.Seq[T]) iter.Seq[T]
- func Map[IN any, OUT any](iterator iter.Seq[IN], transform func(IN) OUT) iter.Seq[OUT]
- func Slice[T any](rangeFunc iter.Seq[T]) []T
- func Unique[T comparable](fn iter.Seq[T]) iter.Seq[T]
- func Values[T any](values ...T) iter.Seq[T]
Constants ¶
This section is empty.
Variables ¶
This section is empty.
Functions ¶
func Filter ¶ added in v0.25.28
Filter returns a new iterator that yields only the items from the input iterator for which the predicate function returns true.
func FilterPointer ¶ added in v0.25.34
FilterPointer returns a new iterator that yields only the items from the input iterator for which the predicate function returns true.
func Join ¶ added in v0.25.28
Join combines multiple iterators into a single iterator that yields all items from each input iterator in sequence.
func Map ¶ added in v0.25.28
Map transforms a rangeFunc of type T into a rangeFunc of type U using the provided transform function.
Types ¶
This section is empty.
Source Files