stream.Reduce

Reduces the stream to a single value by executing a provided function for each value of the stream .

Function signature

    func Reduce(fn interface{}) output

Arguments

Name	Type	Description
fn	func	This function must receive two arguments, the first argument is an accumulator and the second a element of the same type that the elements in the stream. The output of this function will have the same type than the accumulator

Output

Name	Type	Description
output	stream.output	It returns the output (value and error)

Errors

Type	Message
err.items-nil	A nil stream can not be reduced
err.invalid-argument	The reduce operation requires a function as argument
err.invalid-argument	The provided function must retrieve 2 arguments
err.invalid-argument	The provided function must return 1 value
err.invalid-argument	The type of the second argument in the provided function must be %s
err.invalid-argument	The type of the first argument and the output in the provided function must be the same

Examples

package main

import (
	"fmt"
	"github.com/wesovilabs/koazee"
)

var numbers = []int{1, 3, 5, 7, 9}

func main() {
	avg := koazee.Stream().
		With(numbers).
		Reduce(func(acc, item int) int {
			return acc  + item
		}).Int()
	fmt.Printf("The average is %d\n", avg)
}

package main

import (
	"fmt"
	"github.com/wesovilabs/koazee"
)

type genre int

const (
	female genre = iota
	male
)

type primate struct {
	name   string
	age    int
	family string
	genre  genre
}

func newPrimate(name string, age int, family string, genre genre) *primate {
	return &primate{
		name:   name,
		age:    age,
		family: family,
		genre:  genre,
	}
}

var primates = []*primate{
	newPrimate("John", 15, "Capuchin", male),
	newPrimate("Laura", 12, "Squirrel monkey", female),
	newPrimate("Benjamin", 23, "Spider monkey", male),
	newPrimate("George", 19, "Golden Lion Tamarin", male),
	newPrimate("Jane", 33, "Orangutan", female),
	newPrimate("Sarah", 7, "Gibbon", female),
}

func main() {
	filteredPrimates := koazee.StreamOf(primates).
		Filter(func(primate *primate) bool {
			return primate.age > 10 && primate.genre == female
		}).Out().Val().([]*primate)
	for _, primate := range filteredPrimates {
		fmt.Printf("%s is a female and is %d years\n", primate.name, primate.age)
	}

}