Go functional programming library inspired (mostly) on Java Streams
- This plugin requires Go 1.23
- Contains several Java style streams (called steams) and Optionals too.
go get -u github.com/javiorfo/steams@latestMore examples here
package main
import (
"fmt"
"github.com/javiorfo/steams"
"github.com/javiorfo/steams/examples/data"
)
func main() {
steams.OfSlice(data.PersonsWithPets).
Filter(func(p data.Person) bool {
return p.Age > 21
}).
Peek(func(p data.Person) { fmt.Println("After Filter => Person:", p.Name) }).
FlatMapToAny(func(p data.Person) steams.Steam[any] {
results := make(steams.List[any], 0)
for _, v := range p.Pets {
results = append(results, v)
}
return results
}).
Peek(func(p any) { fmt.Println("After FlatMap = Pet:", p.(data.Pet).Name) }).
Filter(func(p any) bool {
animal, ok := p.(data.Pet)
if ok {
if animal.Type == data.CAT {
return true
}
}
return false
}).
Peek(func(p any) { fmt.Println("After second Filter => Pet:", p.(data.Pet).Name) }).
GetCompared(comparator).IfPresentOrElse(print, func() { fmt.Println("No results") })
}
func comparator(a any, b any) bool {
ageA := a.(data.Pet).Age
ageB := b.(data.Pet).Age
return ageA < ageB
}
func print(cat any) {
younger := cat.(data.Pet)
fmt.Printf("The younger cat of the list is %s, age %d", younger.Name, younger.Age)
}// Steam[T] is an interface for a collection of elements of type T,
// providing various methods for functional-style processing.
type Steam[T any] interface {
Filter(predicate func(T) bool) Steam[T]
MapToAny(mapper func(T) any) Steam[any]
MapToInt(mapper func(T) int) Steam[int]
MapToString(mapper func(T) string) Steam[string]
FilterMapToAny(predicate func(T) bool, mapper func(T) any) Steam[any]
FlatMapToAny(mapper func(T) Steam[any]) Steam[any]
FlatMapToInt(mapper func(T) Steam[int]) Steam[int]
FlatMapToString(mapper func(T) Steam[string]) Steam[string]
ForEach(consumer func(T))
Peek(consumer func(T)) Steam[T]
Limit(limit int) Steam[T]
AllMatch(predicate func(T) bool) bool
AnyMatch(predicate func(T) bool) bool
NoneMatch(predicate func(T) bool) bool
TakeWhile(predicate func(T) bool) Steam[T]
DropWhile(predicate func(T) bool) Steam[T]
Reduce(initValue T, acc func(T, T) T) T
Reverse() Steam[T]
Sorted(cmp func(T, T) bool) Steam[T]
GetCompared(cmp func(T, T) bool) opt.Optional[T]
FindFirst() opt.Optional[T]
Last() opt.Optional[T]
Position(predicate func(T) bool) opt.Optional[int]
Skip(n int) Steam[T]
Count() int
Collect() []T
}
// Steam2[K, V] is an interface for a map of elements of type K and V,
// providing various methods for functional-style processing.
type Steam2[K comparable, V any] interface {
Filter(predicate func(K, V) bool) Steam2[K, V]
MapToAny(mapper func(K, V) any) Steam2[K, any]
MapToInt(mapper func(K, V) int) Steam2[K, int]
MapToString(mapper func(K, V) string) Steam2[K, string]
FilterMapToAny(predicate func(K, V) bool, mapper func(K, V) any) Steam2[K, any]
ForEach(consumer func(K, V))
Peek(consumer func(K, V)) Steam2[K, V]
Limit(limit int) Steam2[K, V]
AllMatch(predicate func(K, V) bool) bool
AnyMatch(predicate func(K, V) bool) bool
NoneMatch(predicate func(K, V) bool) bool
Sorted(cmp func(K, K) bool) Steam2[K, V]
GetCompared(cmp func(K, K) bool) opt.Optional[Pair[K, V]]
Count() int
Collect() map[K]V
KeysToSteam() Steam[K]
ValuesToSteam() Steam[V]
ToAnySteam(mapper func(K, V) any) Steam[any]
}func Of[T any](args ...T) Steam[T]
func OfSlice[T any](slice []T) Steam[T]
func OfMap[K comparable, V any](m map[K]V) Steam2[K, V]
func Mapping[T, R any](s Steam[T], mapper func(T) R) Steam[R]
func Distinct[T comparable](s Steam[T]) Steam[T]
func CollectSteamToSteam2[K comparable, V, T any](s Steam[T], keyFunc func(T) K, valueFunc func(T) V) Steam2[K, V]
func CollectSteam2ToSteam[K comparable, V, R any](s Steam2[K, V], mapper func(K, V) R) Steam[R]
func GroupBy[K comparable, V any](s Steam[V], classifier func(V) K) Steam2[K, Steam[V]]
func GroupByCounting[K comparable, V any](s Steam[V], classifier func(V) K) Steam2[K, int]
func Zip[T, R any](s1 Steam[T], s2 Steam[R]) Steam[struct { first T; second R }]