stream

package module
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 Go to latest Published: Mar 29, 2024 License: MIT Imports: 7 Imported by: 0

README

stream

streams package for Go.

docs

Quick Examples

Stream a slice
func ExampleFromSlice() {
	var (
		filterCalled    bool
		transformCalled bool
	)

	stream := FromSlice([]int{3, 8, 11, 24, 37, 42}).
		Filter(func(elem int) bool { filterCalled = true; return elem >= 10 }).
		Skip(1).
		Limit(2).
		Transform(func(elem int) int { transformCalled = true; return elem * 2 })

	fmt.Println(filterCalled)         // NOTE: false is printed here - streams are lazily evaluated
	fmt.Println(transformCalled)      // NOTE: false is printed here - streams are lazily evaluated
	fmt.Println(stream.First().Get()) // NOTE: the stream has now been consumed
	fmt.Println(stream.FirstWhere(func(i int) bool { return i%2 == 1 }).Get())
	fmt.Println(filterCalled)
	fmt.Println(transformCalled)

	// Output:
	// false
	// false
	// 48 true
	// 0 false
	// true
	// true
}
Stream a channel
func ExampleFromChan() {
	var (
		filterCalled    bool
		transformCalled bool
	)

	ch := make(chan int)
	go func() {
		defer close(ch)
		ch <- 3
		ch <- 8
		ch <- 11
		ch <- 24
		ch <- 37
		ch <- 42
	}()

	stream := FromChan(ch).
		Filter(func(elem int) bool { filterCalled = true; return elem >= 10 }).
		Skip(1).
		Limit(2).
		Transform(func(elem int) int { transformCalled = true; return elem * 2 })

	fmt.Println(filterCalled)    // NOTE: false is printed here - streams are lazily evaluated
	fmt.Println(transformCalled) // NOTE: false is printed here - streams are lazily evaluated
	fmt.Println(stream.First().Get())
	fmt.Println(stream.FirstWhere(func(i int) bool { return i%2 == 1 }).Get())
	fmt.Println(stream.First().Get())
	fmt.Println(filterCalled)
	fmt.Println(transformCalled)

	// Output:
	// false
	// false
	// 48 true
	// 0 false
	// 0 false
	// true
	// true
}

Documentation

Index

Examples

Constants

This section is empty.

Variables

This section is empty.

Functions

func And 

func And[T ~bool](cumulative, next T) T

func Append 

func Append[T any, S ~[]T](total, next S) S

func ApplyLeft 

func ApplyLeft[Left, Right, Out any, Func ~func(Left, Right) Out](f Func, left Left) func(Right) Out

ApplyLeft takes a binary function (Left, Right) -> Out, and a value for it's left argument, then returns a unary function Right -> Out.

Example 
package main

import (
	"fmt"

	"github.com/dabbertorres/stream"
)

func main() {
	concat := func(prefix, suffix string) string {
		return prefix + " " + suffix
	}

	commonPrefix := stream.ApplyLeft(concat, "INFO:")

	fmt.Println(commonPrefix("it worked!"))

}

Output:

INFO: it worked!

func ApplyRight 

func ApplyRight[Left, Right, Out any, Func ~func(Left, Right) Out](f Func, right Right) func(Left) Out

ApplyRight takes a binary function, (Left, Right) -> Out, and a value for it's right argument, then returns a unary function Left -> Out.

Example 
package main

import (
	"fmt"

	"github.com/dabbertorres/stream"
)

type Foo struct {
	X int
}

func (f Foo) Add(y int) int { return f.X + y }

func main() {
	f := stream.ApplyRight(Foo.Add, 5)
	result := f(Foo{X: 3})
	fmt.Println(result)

}

Output:

8

func Associate 

func Associate[K comparable, V any, In any](in Stream[In], f func(In) (K, V)) map[K]V

func AssociateBy 

func AssociateBy[K comparable, V any, In any](f func(In) (K, V)) func(Stream[In]) map[K]V

func AssociateByKeyValue 

func AssociateByKeyValue[K comparable, V any](in Stream[KeyValue[K, V]]) map[K]V

func AssociateKeyValue 

func AssociateKeyValue[K comparable, V any](kv KeyValue[K, V]) (K, V)

AssociateKeyValue provides a default function for [KeyValue]s for Associate.

func BitAnd 

func BitAnd[T Integer](cumulative, next T) T

func BitClear 

func BitClear[T Integer](cumulative, next T) T

func BitOr 

func BitOr[T Integer](cumulative, next T) T

func BitXor 

func BitXor[T Integer](cumulative, next T) T

func Chain 

func Chain[Out, Mid, In any, First ~func(In) Mid, Second ~func(Mid) Out](first First, second Second) func(In) Out

Chain creates a unary function In -> Out from two functions such that In -> Mid -> Out.

Example 
package main

import (
	"fmt"

	"github.com/dabbertorres/stream"
)

func main() {
	var (
		isPositive = func(x int) bool { return x > 0 }
		isEven     = func(x int) bool { return x%2 == 0 }
		doubleIt   = func(x int) int { return x * 2 }
	)

	bizLogic := stream.Chain(
		stream.Chain(
			stream.ApplyRight(stream.Stream[int].Filter, isPositive),
			stream.ApplyRight(stream.Stream[int].Filter, isEven),
		),
		stream.ApplyRight(stream.Stream[int].Transform, doubleIt),
	)

	bizLogic(stream.FromSlice([]int{-3, 4, 1, 12})).
		ForEach(func(i int) { fmt.Println(i) })

}

Output:

8
24

func Difference 

func Difference[T Number](cumulative, next T) T

func FilterBy 

func FilterBy[T any](filter func(T) bool) func(Stream[T]) Stream[T]

func FlatMapBy 

func FlatMapBy[In, Out any](mapper func(In) Stream[Out]) func(Stream[In]) Stream[Out]

func Identity 

func Identity[T comparable](v T) T

func KeyValueLess 

func KeyValueLess[K Ordered, V any](lhs, rhs KeyValue[K, V]) bool

KeyValueLess provides a generic LessFunc for [KeyValue]s with an Ordered key.

func LeftShift 

func LeftShift[T Integer](cumulative, next T) T

func MapBy 

func MapBy[In, Out any](mapper func(In) Out) func(Stream[In]) Stream[Out]

func Or 

func Or[T ~bool](cumulative, next T) T

func OrderedLess 

func OrderedLess[T Ordered](lhs, rhs T) bool

OrderedLess provides a generic LessFunc for builtin types that are Ordered.

func Pipe 

func Pipe[Out, Mid, In any, First ~func(In) Mid, Second ~func(Mid) Out](in In, first First, second Second) Out

Pipe applies in to first, passes its result to second, and returns second's result.

Example

ExamplePipe is the same logic as [ExampleChain], but shows the readability improvement of Pipe in certain cases. 

package main

import (
	"fmt"

	"github.com/dabbertorres/stream"
)

func main() {
	var (
		isPositive = func(x int) bool { return x > 0 }
		isEven     = func(x int) bool { return x%2 == 0 }
		doubleIt   = func(x int) int { return x * 2 }
	)

	stream.Pipe(
		stream.FromSlice([]int{-3, 4, 1, 12}),
		stream.Chain(
			stream.ApplyRight(stream.Stream[int].Filter, isPositive),
			stream.ApplyRight(stream.Stream[int].Filter, isEven),
		),
		stream.ApplyRight(stream.Stream[int].Transform, doubleIt),
	).ForEach(func(i int) { fmt.Println(i) })

}

Output:

8
24

func Product 

func Product[T Number](cumulative, next T) T

func Quotient 

func Quotient[T Number](cumulative, next T) T

func Remainder 

func Remainder[T Integer](cumulative, next T) T

func RightShift 

func RightShift[T Integer](cumulative, next T) T

func SortedBy 

func SortedBy[T any](less LessFunc[T]) func(Stream[T]) Stream[T]

func Sum 

func Sum[T Number | ~string](cumulative, next T) T

func TransformBy 

func TransformBy[T any](transform func(T) T) func(Stream[T]) Stream[T]

func ValueMapper 

func ValueMapper[K comparable, InV, OutV any](f func(InV) OutV) func(KeyValue[K, InV]) KeyValue[K, OutV]

ValueMapper is a helper wrapper to simplify mapping only the value of a KeyValue.

func ValueTransform 

func ValueTransform[K comparable, V any](f func(V) V) func(KeyValue[K, V]) KeyValue[K, V]

ValueTransform is a helper wrapper to simplify transforming only the value of a KeyValue.

Types

type Associater 

type Associater[In any, K comparable, V any] struct {
	// contains filtered or unexported fields
}

func (Associater[In, K, V]) By 

func (a Associater[In, K, V]) By(f func(In) (K, V)) map[K]V

func (Associater[In, K, V]) ByTo 

func (a Associater[In, K, V]) ByTo(to map[K]V, f func(In) (K, V))

type Decoder 

type Decoder interface {
	Decode(any) error
}

Decoder is implemented by most of the encoding/* packages in the standard library, and often by third-party packages providing similar capabilities.

type Float 

type Float interface {
	~float32 | ~float64
}

type Integer 

type Integer interface {
	Signed | Unsigned
}

type KeyValue 

type KeyValue[K comparable, V any] struct {
	Key K
	Val V
}

type KeyValueAssociater 

type KeyValueAssociater[K comparable, V any] struct {
	// contains filtered or unexported fields
}

KeyValueAssociater is a helper to reduce noise when using Associate with [KeyValue]s.

func AssociateFromKeyValue 

func AssociateFromKeyValue[K comparable, V any](in Stream[KeyValue[K, V]]) KeyValueAssociater[K, V]

func (KeyValueAssociater[K, V]) By 

func (a KeyValueAssociater[K, V]) By(f func(K, V) (K, V)) map[K]V

By creates a map[K]V from the Stream, with keys and values defined by f. If f is nil, the identity function is used (K and V without any changes).

func (KeyValueAssociater[K, V]) ByTo 

func (a KeyValueAssociater[K, V]) ByTo(to map[K]V, f func(K, V) (K, V))

ByTo fills to from the Stream, with keys and values defined by f. If f is nil, the identity function is used (K and V without any changes).

type LessFunc 

type LessFunc[T any] func(lhs, rhs T) bool

LessFunc is a function that returns true when lhs is less than rhs.

type MinMax 

type MinMax[T any] struct {
	Min T
	Max T
}

type Number 

type Number interface {
	Integer | Float
}

type Optional 

type Optional[T any] struct {
	// contains filtered or unexported fields
}

func None 

func None[T any]() Optional[T]

func OptionalFromPointer 

func OptionalFromPointer[T any](ptr *T) Optional[T]

func Some 

func Some[T any](value T) Optional[T]

func (Optional[T]) Get 

func (o Optional[T]) Get() (T, bool)

func (Optional[T]) GetOrDefault 

func (o Optional[T]) GetOrDefault(defaultVal T) T

func (Optional[T]) GetOrDefaultFunc 

func (o Optional[T]) GetOrDefaultFunc(defaultFunc func() T) T

func (Optional[T]) IfNone 

func (o Optional[T]) IfNone(f func())

func (Optional[T]) IfSome 

func (o Optional[T]) IfSome(f func(T))

func (Optional[T]) MarshalJSON 

func (o Optional[T]) MarshalJSON() ([]byte, error)

func (Optional[T]) MustGet 

func (o Optional[T]) MustGet() T

func (Optional[T]) None 

func (o Optional[T]) None() bool

func (Optional[T]) Some 

func (o Optional[T]) Some() bool

func (*Optional[T]) UnmarshalJSON 

func (o *Optional[T]) UnmarshalJSON(data []byte) error

type Ordered 

type Ordered interface {
	Number | ~string
}

type Signed 

type Signed interface {
	~int | ~int8 | ~int16 | ~int32 | ~int64
}

type Stream 

type Stream[T any] struct {
	// contains filtered or unexported fields
}

func ApplyTo 

func ApplyTo[T any, Func ~func(Stream[T]) Stream[T]](in Stream[T], f Func) Stream[T]

func Filter 

func Filter[T any](in Stream[T], filter func(T) bool) Stream[T]

func FlatMap 

func FlatMap[In, Out any](in Stream[In], mapper func(In) Stream[Out]) Stream[Out]

func Flatten 

func Flatten[T any](in Stream[Stream[T]]) Stream[T]

func FromChan 

func FromChan[T any](src <-chan T) Stream[T]
Example 
var (
	filterCalled    bool
	transformCalled bool
)

ch := make(chan int)
go func() {
	defer close(ch)
	ch <- 3
	ch <- 8
	ch <- 11
	ch <- 24
	ch <- 37
	ch <- 42
}()

stream := FromChan(ch).
	Filter(func(elem int) bool { filterCalled = true; return elem >= 10 }).
	Skip(1).
	Limit(2).
	Transform(func(elem int) int { transformCalled = true; return elem * 2 })

fmt.Println(filterCalled)    // NOTE: false is printed here - streams are lazily evaluated
fmt.Println(transformCalled) // NOTE: false is printed here - streams are lazily evaluated
fmt.Println(stream.First().Get())
fmt.Println(stream.FirstWhere(func(i int) bool { return i%2 == 1 }).Get())
fmt.Println(stream.First().Get())
fmt.Println(filterCalled)
fmt.Println(transformCalled)

Output:

false
false
48 true
0 false
0 false
true
true

func FromDecoder 

func FromDecoder[T any](dec Decoder, onError func(error)) Stream[T]

FromDecoder reads T values from the given Decoder until an error is encountered, which results in the end of the Stream. If the error is not io.EOF, onError is called with the error. onError may be nil, in which case the error is silently dropped.

Example 
type bar struct {
	Foo int `json:"foo"`
}

data := []byte(`
    {"foo": 7}
    {"foo": 5}
    {"foo": 7}
    {"foo": -13}
`)

results := FromDecoder[bar](json.NewDecoder(bytes.NewReader(data)), nil).
	Distinct().
	Filter(func(b bar) bool { return b.Foo >= 0 }).
	Collect()

fmt.Println(results)

Output:

[{7} {5}]

func FromFunc 

func FromFunc[T any](f func() Optional[T]) Stream[T]
Example 
var transformCalled bool

i := 1
stream := FromFunc(func() Optional[int] {
	v := i
	i *= 2
	if v <= 64 {
		return Some(v)
	}
	return None[int]()
}).Skip(1).
	Limit(10).
	Transform(func(elem int) int { transformCalled = true; return elem * 3 })

fmt.Println(transformCalled) // NOTE: false is printed here - streams are lazily evaluated
fmt.Println(stream.Collect())
fmt.Println(transformCalled)

Output:

false
[6 12 24 48 96 192]
true

func FromMap 

func FromMap[K comparable, V any, M ~map[K]V](src M) Stream[KeyValue[K, V]]

func FromOptional 

func FromOptional[T any](opt Optional[T]) Stream[T]

func FromSlice 

func FromSlice[T any, S ~[]T](src S) Stream[T]
Example 
var (
	filterCalled    bool
	transformCalled bool
)

stream := FromSlice([]int{3, 8, 11, 24, 37, 42}).
	Filter(func(elem int) bool { filterCalled = true; return elem >= 10 }).
	Skip(1).
	Limit(2).
	Transform(func(elem int) int { transformCalled = true; return elem * 2 })

fmt.Println(filterCalled)         // NOTE: false is printed here - streams are lazily evaluated
fmt.Println(transformCalled)      // NOTE: false is printed here - streams are lazily evaluated
fmt.Println(stream.First().Get()) // NOTE: the stream has now been consumed
fmt.Println(stream.FirstWhere(func(i int) bool { return i%2 == 1 }).Get())
fmt.Println(filterCalled)
fmt.Println(transformCalled)

Output:

false
false
48 true
0 false
true
true

func Join 

func Join[T any](streams ...Stream[T]) Stream[T]

func Map 

func Map[In, Out any](in Stream[In], mapper func(In) Out) Stream[Out]

func Sorted 

func Sorted[T any](in Stream[T], less LessFunc[T]) Stream[T]

func Transform 

func Transform[T any](in Stream[T], transform func(T) T) Stream[T]

func (Stream[T]) All 

func (s Stream[T]) All(f func(T) bool) (allMatched bool)

func (Stream[T]) Any 

func (s Stream[T]) Any(f func(T) bool) (anyMatched bool)

func (Stream[T]) Append 

func (s Stream[T]) Append(out []T) []T

func (Stream[T]) Collect 

func (s Stream[T]) Collect() (out []T)

func (Stream[T]) Distinct 

func (s Stream[T]) Distinct() Stream[T]

func (Stream[T]) DropWhile 

func (s Stream[T]) DropWhile(f func(T) bool) Stream[T]

func (Stream[T]) Filter 

func (s Stream[T]) Filter(filter func(T) bool) Stream[T]

func (Stream[T]) First 

func (s Stream[T]) First() (opt Optional[T])

func (Stream[T]) FirstWhere 

func (s Stream[T]) FirstWhere(f func(T) bool) (opt Optional[T])

func (Stream[T]) ForEach 

func (s Stream[T]) ForEach(f func(T))

func (Stream[T]) Limit 

func (s Stream[T]) Limit(n int) Stream[T]

func (Stream[T]) Max 

func (s Stream[T]) Max(less LessFunc[T]) (max Optional[T])

func (Stream[T]) Min 

func (s Stream[T]) Min(less LessFunc[T]) (min Optional[T])

func (Stream[T]) MinMax 

func (s Stream[T]) MinMax(less LessFunc[T]) (minMax Optional[MinMax[T]])

func (Stream[T]) None 

func (s Stream[T]) None(f func(T) bool) (noneMatched bool)

func (Stream[T]) Range 

func (s Stream[T]) Range() <-chan T

func (Stream[T]) RangeTo 

func (s Stream[T]) RangeTo(ch chan<- T)

func (Stream[T]) Reduce 

func (s Stream[T]) Reduce(start T, reducer func(cumulative T, next T) T) T

func (Stream[T]) Skip 

func (s Stream[T]) Skip(n int) Stream[T]

func (Stream[T]) Sorted 

func (s Stream[T]) Sorted(less LessFunc[T]) Stream[T]

func (Stream[T]) TakeWhile 

func (s Stream[T]) TakeWhile(f func(T) bool) Stream[T]

func (Stream[T]) Transform 

func (s Stream[T]) Transform(f func(T) T) Stream[T]

type Unsigned 

type Unsigned interface {
	~uint | ~uint8 | ~uint16 | ~uint32 | ~uint64 | ~uintptr
}

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