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
See also:
- 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
Why this name?
I love short name for such utility library. This name is similar to "Monad Go" and no Go package currently uses this name.
π‘ 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]
π Install
go get github.com/samber/mo@v1This 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.
π‘ Quick start
You can import mo using:
import (
"github.com/samber/mo"
)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.
π€ 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.
Constructors:
mo.Some()doc - playmo.None()doc - playmo.TupleToOption()doc - playmo.EmptyableToOption()doc - playmo.PointerToOption()doc - play
Methods:
.IsPresent()doc - play.IsAbsent()doc - play.Size()doc - play.Get()doc - play.MustGet()doc - play.OrElse()doc - play.OrEmpty()doc - play.ForEach()doc.Match()doc - play.Map()doc - play.MapNone()doc - play.FlatMap()doc - play.MarshalJSON()doc.UnmarshalJSON()doc.MarshalText()doc.UnmarshalText()doc.MarshalBinary()doc.UnmarshalBinary()doc.GobEncode()doc.GobDecode()doc.Scan()doc.Value()doc
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].
Constructors:
Methods:
.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.Match()doc - play.Map()doc - play.MapErr()doc - play.FlatMap()doc - play
Either[L any, R any]
Either respresents a value of 2 possible types. An instance of Either is an instance of either A or B.
Constructors:
Methods:
.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
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.NewEither3Arg1[A, B, C](A)mo.NewEither3Arg2[A, B, C](B)mo.NewEither3Arg3[A, B, C](C)mo.NewEither4Arg1[A, B, C, D](A)mo.NewEither4Arg2[A, B, C, D](B)- ...
Methods:
.IsArgX()doc.ArgX()doc.MustArgX()doc.Unpack()doc.ArgXOrElse()doc.ArgXOrEmpty()doc.ForEach()doc.Match()doc.MapArgX()doc
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
Methods:
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
Methods:
.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
Methods:
.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:
π© Benchmark
// @TODO
This library does not use reflect package. We don't expect overhead.
οΏ½? Contributing
- Ping me on twitter @samuelberthe (DMs, mentions, whatever :))
- Fork the project
- Fix open issues or request new features
Don't hesitate ;)
With Docker
docker-compose run --rm devWithout Docker
# Install some dev dependencies
make tools
# Run tests
make test
# or
make watch-testπ€ Contributors
π« Show your support
Give a
οΏ½? License
Copyright Β© 2022 Samuel Berthe.
This project is MIT licensed.
