Maybe

Simple zero dependency struct-based generic monad implementation in Go.

Installation

go get -u github.com/mono83/maybe

Usage

Instantiation

There are two main ways to create maybe.Maybe monadic container - it is either call to maybe.Nothing() or maybe.Just(value). First will create empty monad, while second one will produce not empty monad with given value.

Pay attention, that maybe.Just does not verify content of passed value, so constructions like maybe.Just[error](nil) can create not empty monads with nil value within. To avoid this behaviour use maybe.Nilable, that will perform nil check of given value.

In addition to raw instantiation, this library provide mapping constructor maybe.Map, able to convert Maybe from one type to another using mapping function

n := maybe.Nothing[string]()    // String type, but empty
i := maybe.Just(1)              // Int type
s := maybe.Map(i, strconv.Itoa) // String type

JSON

JSON bindings can be accessed using github.com/mono83/maybe/json package:

import "github.com/mono83/maybe/json"

type Request struct {
	ID       int
	ParentID json.Maybe[int]
}

Benchmarks

$ go test -bench=. -benchmem
goos: linux
goarch: amd64
pkg: github.com/mono83/maybe
cpu: Intel(R) Core(TM) i5-10400F CPU @ 2.90GHz
BenchmarkNothing-12             1000000000               0.2704 ns/op          0 B/op          0 allocs/op
BenchmarkJust-12                904382658                1.313 ns/op           0 B/op          0 allocs/op
BenchmarkPtr-12                 1000000000               1.051 ns/op           0 B/op          0 allocs/op
BenchmarkPtrNil-12              755984685                1.578 ns/op           0 B/op          0 allocs/op
BenchmarkNilableInt-12          72761029                16.37 ns/op            8 B/op          0 allocs/op
BenchmarkNilableNil-12          275986280                4.157 ns/op           0 B/op          0 allocs/op
PASS
ok      github.com/mono83/maybe 6.931s