README
¶
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
Documentation
¶
Index ¶
- type Maybe
- func (m Maybe[T]) Filter(predicate func(T) bool) Maybe[T]
- func (m Maybe[T]) FilterNotNil() Maybe[T]
- func (m Maybe[T]) Get() (T, bool)
- func (m Maybe[T]) IfPresent(consume func(T)) Maybe[T]
- func (m Maybe[T]) IfPresentOrElse(consume func(T), els func()) Maybe[T]
- func (m Maybe[T]) IsEmpty() bool
- func (m Maybe[T]) IsPresent() bool
- func (m Maybe[T]) MapToAny(mapper func(T) any) Maybe[any]
- func (m Maybe[T]) MapToFloat32(mapper func(T) float32) Maybe[float32]
- func (m Maybe[T]) MapToFloat64(mapper func(T) float64) Maybe[float64]
- func (m Maybe[T]) MapToInt(mapper func(T) int) Maybe[int]
- func (m Maybe[T]) MapToInt16(mapper func(T) int16) Maybe[int16]
- func (m Maybe[T]) MapToInt32(mapper func(T) int32) Maybe[int32]
- func (m Maybe[T]) MapToInt64(mapper func(T) int64) Maybe[int64]
- func (m Maybe[T]) MapToString(mapper func(T) string) Maybe[string]
- func (m Maybe[T]) MapToUint(mapper func(T) uint) Maybe[uint]
- func (m Maybe[T]) MapToUint16(mapper func(T) uint16) Maybe[uint16]
- func (m Maybe[T]) MapToUint32(mapper func(T) uint32) Maybe[uint32]
- func (m Maybe[T]) MapToUint64(mapper func(T) uint64) Maybe[uint64]
- func (m Maybe[T]) Or(supply func() Maybe[T]) Maybe[T]
- func (m Maybe[T]) OrElse(other T) T
- func (m Maybe[T]) OrElseGet(supply func() T) T
- func (m Maybe[T]) Value() T
Constants ¶
This section is empty.
Variables ¶
This section is empty.
Functions ¶
This section is empty.
Types ¶
type Maybe ¶
type Maybe[T any] struct { // contains filtered or unexported fields }
Maybe is generic monadic container for value or it's absence
func Just ¶
Just constructs new Maybe with given value. This constructor will create non-empty Maybe even for nil value, for protection use Nilable instead.
func Nilable ¶
Nilable constructs new Maybe and performs emptiness check of given data. Will produce empty Maybe for following cases: - nil value - zero-length slice - zero-length map
func (Maybe[T]) Filter ¶
Filter applies given predicate of container returning original value only if predicate resulted in true.
func (Maybe[T]) FilterNotNil ¶
FilterNotNil filters Maybe leaving only non-nil value.
func (Maybe[T]) IfPresentOrElse ¶
IfPresent invokes given consumer callback if value present and plain func if container empty.
func (Maybe[T]) MapToFloat32 ¶
func (Maybe[T]) MapToFloat64 ¶
func (Maybe[T]) Or ¶
Or produces Maybe: 1. If current not empty - return it 2. If current is empty - return produced by supply func 3. Nothing if current is empty and supply function is nil
func (Maybe[T]) OrElse ¶
func (m Maybe[T]) OrElse(other T) T
OrElse returns value from Maybe if it presents, otherwise given value is returned.
Source Files
Directories