functools's Introduction

functools

functools is a simple Go library that brings you your favourite functional paradigms without sacrificing type-safety using interface{} or reflect

Made possible by Go 1.18 using the newly introduced generics.

Features

Any
All
Count
Filter
ForEach
Map
Reduce
ReduceRight
Sum
Chunk

Installation

go get -u github.com/rakeeb-hossain/functools

Usage

import (
    "github.com/rakeeb-hossain/functools"
    "fmt"
)

type User struct {
	username     string
	hasPortfolio bool
}

var users = []User{
		{"gopher", true},
		{"rakeeb", false},
		{"jack", true}}

func main() {
    // Count users with linked portfolios
    fmt.Printf("num users with linked portfolios: %d", 
        functools.Count(users, func(u User) bool { return u.hasPortfolio }))

    // Print usernames of users with linked portfolios
    functools.ForEach(
        functools.Filter(users, func(u User) bool { return u.hasPortfolio }),
        func(u User) { fmt.Printf("%s has a linked portfolio\n", u.username) })
}

Documentation

https://pkg.go.dev does not yet support Go 1.18 packages that use generics: golang/go#48264

For now, documentation is provided via comments and by running go doc -all from the package directory.

Contributing

Please see CONTRIBUTING

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functools's Issues

Filter: redundant memory allocation

You should not allocate new slice, it can be too expensive, just reuse old one

func Filter[T any](slice []T, predicate func(T) bool) []T {
	res := slice[:0]
	for _, v := range slice {
		if predicate(v) {
			res = append(res, v)
		}
	}
	return res
}

`Chunk` func

Chunk consumes a slice of a generic type and returns a slice composed of multiple chunks of a user-specified size

Vacuously, empty slices return empty regardless of the chunk size.

When the chunk size is zero or negative, return an empty slice

exp:

slice := []int{1, 2, 3, 4}
chunk := Chunk(slice, 2) // []int{{1,2}, {3, 4}}

chunk = Chunk(slice, 3) // []int{{1, 2, 3}, {4}}

chunk = Chunk(slice, 10) // []int{{1, 2, 3, 4}}

chunk = Chunk(slice, 0) // []int{}

ReduceRight

I think ReduceRight is a good addition for completeness sake.

Sometimes the order of evaluation for a reduce changes the result.

e.g.

strConcat := func(a, b string) string { return a + b }

slice := []string{"a", "b", "c"}

Reduce(slice, "", strConcat) // Output: "abc"

ReduceRight(slice, "", strConcat) // Output: "cba"

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