sliceutil

sliceutil

Generic slice operations for Go — Map, Filter, Reduce, All, Any, and Chunk.

Problem

Go's type system supports generics (since 1.18) but the standard library does not include common higher-order slice functions. Every project ends up reimplementing map, filter, and reduce by hand. This package provides a small, stdlib-only set of generic slice utilities with a clean, idiomatic API.

Quick start

import "github.com/azghr/forge/sliceutil"

ints := []int{1, 2, 3, 4}

sqs := sliceutil.Map(ints, func(x int) int { return x * x })
// sqs == []int{1, 4, 9, 16}

evens := sliceutil.Filter(ints, func(x int) bool { return x%2 == 0 })
// evens == []int{2, 4}

sum := sliceutil.Reduce(ints, 0, func(acc, x int) int { return acc + x })
// sum == 10

API

Functions

All functions accept a slice S ~[]E (any concrete type whose underlying type is []E) and never mutate the input.

• Map[S ~[]E, E, R any](s S, f func(E) R) []R — apply f to each element, return new slice of results.
• Filter[S ~[]E, E any](s S, f func(E) bool) S — return new slice with elements where f returns true.
• Reduce[S ~[]E, E, R any](s S, init R, f func(R, E) R) R — accumulate elements left-to-right, starting with init.
• All[S ~[]E, E any](s S, f func(E) bool) bool — true if f holds for every element (vacuously true for empty slices). Short-circuits.
• Any[S ~[]E, E any](s S, f func(E) bool) bool — true if f holds for at least one element. Short-circuits.
• Chunk[S ~[]E, E any](s S, n int) []S — split into chunks of size n (last may be smaller). Returns nil when n <= 0 or s is empty.

Error semantics

None of the functions return errors. If the provided f panics, the panic propagates to the caller.

Performance

Function	Time	Extra space	Notes
Map	O(n)	O(n)	Allocates result slice
Filter	O(n)	O(n)	Pre-allocates capacity
Reduce	O(n)	O(1)	In-place accumulator
All	O(n)	O(1)	Short-circuits on false
Any	O(n)	O(1)	Short-circuits on true
Chunk	O(n)	O(n)	Shares backing with input

All functions are concurrency-safe (no shared state).