🦄 Monads and popular FP abstractions, powered by Go 1.18+ Generics (Option, Result, Either...)
mo - Monads
🦄 samber/mo brings monads and popular FP abstractions to Go projects. samber/mo uses the recent Go 1.18+ Generics.
Inspired by:
- Scala
- Rust
- FP-TS
- samber/ro: Reactive Programming for Go: declarative and composable API for event-driven applications
- samber/lo: A Lodash-style Go library based on Go 1.18+ Generics
- samber/do: A dependency injection toolkit based on Go 1.18+ Generics
- samber/cc-skills-golang: AI Agent Skills for Golang
Why this name?
I love short name for such utility library. This name is similar to "Monad Go" and no Go package uses this name.
💡 Features
We currently support the following data types:
Option[T](Maybe)Result[T]Either[A, B]EitherX[T1, ..., TX](With X between 3 and 5)Future[T]IO[T]IOEither[T]Task[T]TaskEither[T]State[S, A]
🚀 Install
go get github.com/samber/mo@v1
AI Agent Skill
npx skills add https://github.com/samber/cc-skills-golang --skill golang-samber-moThis library is v1 and follows SemVer strictly.
No breaking changes will be made to exported APIs before v2.0.0.
This library has no dependencies except the Go std lib.
💡 Quick start
You can import mo using:
import (
"github.com/samber/mo"
)Quick example using the option sub-package Pipe3 to compose transformations:
import (
"github.com/samber/mo"
"github.com/samber/mo/option"
)
out := option.Pipe3( mo.Some(21), option.Map(func(v int) int { return v * 2 }), option.FlatMap(func(v int) mo.Option[int] { return mo.None[int]() }), option.Map(func(v int) int { return v + 21 }), ) // out == None[int]
Then use one of the helpers below:
option1 := mo.Some(42)
// Some(42)
option1. FlatMap(func (value int) Option[int] { return Some(value*2) }). FlatMap(func (value int) Option[int] { return Some(value%2) }). FlatMap(func (value int) Option[int] { return Some(value+21) }). OrElse(1234) // 21
option2 := mo.None[int]() // None
option2.OrElse(1234) // 1234
option3 := option1.Match( func(i int) (int, bool) { // when value is present return i * 2, true }, func() (int, bool) { // when value is absent return 0, false }, ) // Some(42)
More examples in documentation.
Tips for lazy developers
I cannot recommend it, but in case you are too lazy for repeating mo. everywhere, you can import the entire library into the namespace.
import (
. "github.com/samber/mo"
)I take no responsibility on this junk. 😁 💩
🤠 Documentation and examples
GoDoc: https://godoc.org/github.com/samber/mo
Option[T any]
Option is a container for an optional value of type T. If value exists, Option is of type Some. If the value is absent, Option is of type None.
Implements:
mo.Foldable[T, U]
mo.Some()doc - playmo.None()doc - playmo.TupleToOption()doc - playmo.EmptyableToOption()doc - playmo.PointerToOption()doc - play
.IsPresent()doc - play.IsSome()doc - play.IsAbsent()doc - play.IsNone()doc - play.Size()doc - play.Get()doc - play.MustGet()doc - play.OrElse()doc - play.OrEmpty()doc - play.ToPointer()doc - play.ForEach()doc.Match()doc - play.Map()doc - play.MapNone()doc - play.MapValue()doc.FlatMap()doc - play.MarshalJSON()doc.UnmarshalJSON()doc.MarshalText()doc.UnmarshalText()doc.MarshalBinary()doc.UnmarshalBinary()doc.GobEncode()doc.GobDecode()doc.Scan()doc.Value()doc
mo.FoldT, U, R any R, failureFunc func(T) R) Rdoc
option (transformations and pipes):
option.Map()()docoption.FlatMap()()docoption.Match()()docoption.FlatMatch()()docoption.Pipe1..Pipe10()docs
Result[T any]
Result respresent a result of an action having one of the following output: success or failure. An instance of Result is an instance of either Ok or Err. It could be compared to Either[error, T].
Implements:
mo.Foldable[T, U]
mo.Ok()doc - playmo.Err()doc - playmo.Errf()doc - playmo.TupleToResult()doc - playmo.Try()doc - play
.IsOk()doc - play.IsError()doc - play.Error()doc - play.Get()doc - play.MustGet()doc - play.OrElse()doc - play.OrEmpty()doc - play.ToEither()doc - play.ForEach()doc - play.Match()doc - play.Map()doc - play.MapValue()doc - play.MapErr()doc - play.FlatMap()doc - play
mo.FoldT, U, R any R, failureFunc func(T) R) Rdocmo.DoT any T) (result mo.Result[T])doc
result (transformations and pipes):
result.Map()()docresult.FlatMap()()docresult.Match()()docresult.FlatMatch()()docresult.Pipe1..Pipe10()docs
Either[L any, R any]
Either represents a value of 2 possible types. An instance of Either is an instance of either A or B.
Implements:
mo.Foldable[T, U]
.IsLeft()doc.IsRight()doc.Left()doc.Right()doc.MustLeft()doc.MustRight()doc.Unpack()doc.LeftOrElse()doc.RightOrElse()doc.LeftOrEmpty()doc.RightOrEmpty()doc.Swap()doc.ForEach()doc.Match()doc.MapLeft()doc.MapRight()doc
mo.FoldT, U, R any R, failureFunc func(T) R) Rdoc
either (transformations and pipes):
either.MapLeft()()doceither.MapRight()()doceither.Match()()doceither.Swap()()doceither.Pipe1..Pipe10()docs
EitherX[T1, ..., TX] (With X between 3 and 5)
EitherX respresents a value of X possible types. For example, an Either3 value is either T1, T2 or T3.
Constructors:
mo.NewEitherXArgY()doc. Eg:
mo.NewEither3Arg1A, B, C
- mo.NewEither3Arg2A, B, C
- mo.NewEither3Arg3A, B, C
- mo.NewEither4Arg1A, B, C, D
- mo.NewEither4Arg2A, B, C, D
- ...
Methods:
.IsArgX()doc.ArgX()doc.MustArgX()doc.Unpack()doc.ArgXOrElse()doc.ArgXOrEmpty()doc.ForEach()doc.Match()doc.MapArgX()doc
either3, either4, either5 (transformations and pipes):
- either3 docs: https://pkg.go.dev/github.com/samber/mo/either3
either3.Match()() doc
- either3.MapArg1()() doc
- either3.MapArg2()() doc
- either3.MapArg3()() doc
- either3.Pipe1..Pipe10() docs
- either4 docs: https://pkg.go.dev/github.com/samber/mo/either4
either4.Match()() doc
- either4.MapArg1()() doc
- either4.MapArg2()() doc
- either4.MapArg3()() doc
- either4.Pipe1..Pipe10() docs
- either5 docs: https://pkg.go.dev/github.com/samber/mo/either5
either5.Match()() doc
- either5.MapArg1()() doc
- either5.MapArg2()() doc
- either5.MapArg3()() doc
- either5.Pipe1..Pipe10() docs
Future[T any]
Future represents a value which may or may not currently be available, but will be available at some point, or an exception if that value could not be made available.
Constructors:
mo.NewFuture()doc
IO[T any]
IO represents a non-deterministic synchronous computation that can cause side effects, yields a value of type R and never fails.
Constructors:
Methods:.Run()doc
IOEither[T any]
IO represents a non-deterministic synchronous computation that can cause side effects, yields a value of type R and can fail.
Constructors:
mo.NewIOEither()docmo.NewIOEither1()docmo.NewIOEither2()docmo.NewIOEither3()docmo.NewIOEither4()docmo.NewIOEither5()doc
.Run()doc
Task[T any]
Task represents a non-deterministic asynchronous computation that can cause side effects, yields a value of type R and never fails.
Constructors:
mo.NewTask()docmo.NewTask1()docmo.NewTask2()docmo.NewTask3()docmo.NewTask4()docmo.NewTask5()docmo.NewTaskFromIO()docmo.NewTaskFromIO1()docmo.NewTaskFromIO2()docmo.NewTaskFromIO3()docmo.NewTaskFromIO4()docmo.NewTaskFromIO5()doc
.Run()doc
TaskEither[T any]
TaskEither represents a non-deterministic asynchronous computation that can cause side effects, yields a value of type R and can fail.
Constructors:
Methods:State[S any, A any]
State represents a function (S) -> (A, S), where S is state, A is result.
Constructors:
Methods:Foldable[T, U]
Foldable represents a type that can be folded into a single value based on its state.
mo.FoldT, U, R any R, failureFunc func(T) R) Rdoc
🛩 Benchmark
// @TODO
This library does not use reflect package. We don't expect overhead.
🤝 Contributing
- Ping me on Twitter @samuelberthe (DMs, mentions, whatever :))
- Fork the project
- Fix open issues or request new features
# Install some dev dependencies
make tools
Run tests
make test
or
make watch-test👤 Contributors
💫 Show your support
Give a ⭐️ if this project helped you!
📝 License
Copyright © 2022 Samuel Berthe.
This project is MIT licensed.
