functools/functools.go

// Copyright 2022 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

package functools

import (
	"golang.org/x/exp/constraints"
	"golang.org/x/exp/slices"
)

// Filter returns a new slice containing all the elements of `original` for
// which `f` returns true.
func Filter[T any](original []T, f func(T) bool) []T {
	var filtered []T
	for _, element := range original {
		if f(element) {
			filtered = append(filtered, element)
		}
	}
	return filtered
}

// SortBy sorts the given slice in-place, using the return value of `getter`
// as the key by which elements are sorted.
func SortBy[T any, C constraints.Ordered](slice []T, getter func(T) C) {
	slices.SortFunc(slice, func(a, b T) bool {
		return getter(a) < getter(b)
	})
}