Listy – Functional programming with Golang slices

Synopsis

import (
	"fmt"

	"github.com/xdg/listy"
)

func Example() {

	strings := []string{"foo", "bar", "bar", "baz"}
	ints := []int{3, 1, 4, 1, 5, 9, 2, 6, 5}

	// Wrap slices in listy types to "box" them

	xs := listy.S(strings)
	ys := listy.I(ints)

	// Call methods on boxed types. Chain them as needed.

	if xs.Contains("baz") {
		fmt.Println("Has 'baz'")
	}

	if ys.Contains(9) {
		fmt.Println("Has '9'")
	}

	uxs := xs.Uniq()
	uys := ys.Uniq()

	mxs := uxs.Reverse().Map(func(s string) string { return fmt.Sprintf("'%s'", s) })
	mys := uys.Reverse().Map(func(i int) int { return -1 * i })

	// Unbox them to get built-in slice types back

	fmt.Println("Unique xs:", uxs.Unbox())
	fmt.Println("Unique ys:", uys.Unbox())

	fmt.Println("Reverse mapped unique xs:", mxs.Unbox())
	fmt.Println("Reverse mapped unique ys:", mys.Unbox())

	// Output:
	// Has 'baz'
	// Has '9'
	// Unique xs: [foo bar baz]
	// Unique ys: [3 1 4 5 9 2 6]
	// Reverse mapped unique xs: ['baz' 'bar' 'foo']
	// Reverse mapped unique ys: [-6 -2 -9 -5 -4 -1 -3]
}

Description

This is an experiment-in-progress writing and generating functional list manipulation functions for Go slices. The list of functions is inspired by a subset of the Data.List package from Haskell, and similar libraries I've seen in other languages.

The emphasis of this library is on expressiveness and clarity. With one exception (Swap, for Sort.Interface), methods treat inputs as immutable, returning copies rather than mutating slices in place.

Copyright and License

Copyright 2017 by David A. Golden. All rights reserved.

Licensed under the Apache License, Version 2.0 (the "License"). You may obtain a copy of the License at http://www.apache.org/licenses/LICENSE-2.0