Slices on Nalar

Append Iterator Values to Go Slices with slices.AppendSeq

Thu, 10 Sep 2026 00:00:00 +0700

An iterator is convenient while data is flowing through a pipeline, but sooner or later you may need those values in a slice. If you already have a destination slice, collecting the iterator separately and then appending it creates an unnecessary intermediate step.

Go 1.23 added slices.AppendSeq for exactly this boundary. It consumes an iter.Seq, appends each yielded value to an existing slice, and returns the resulting slice.

What slices.AppendSeq does

The function has a compact signature:

Process Go Slices in Batches with slices.Chunk

Thu, 10 Sep 2026 00:00:00 +0700

Batching a slice sounds simple until the loop starts collecting edge cases: the final batch may be short, an empty input needs sensible behavior, and careless subslicing can leave each batch with capacity to overwrite later elements.

Go 1.23 added slices.Chunk, which handles that bookkeeping and exposes the batches as an iterator. If you already have the data in a slice and want to process consecutive groups without first building a [][]T, it’s a useful small tool.

Remove Consecutive Duplicates in Go with slices.Compact

Thu, 10 Sep 2026 00:00:00 +0700

If a Go slice contains repeated values next to each other, you don’t need to write an index-heavy loop to collapse them. Since Go 1.21, slices.Compact handles that operation directly for comparable element types.

The word consecutive matters. Given []string{"api", "api", "web", "api"}, the result is []string{"api", "web", "api"}. The last "api" stays because it belongs to a different run. slices.Compact isn’t a general-purpose “unique values” function.

What slices.Compact actually does

slices.Compact replaces each consecutive run of equal elements with its first element. It modifies the slice’s backing array and returns a slice with the resulting length.