example_reduce_group_test.go

package goiteratorhelper_test

import (
	"fmt"
	"slices"

	"github.com/ngicks/go-iterator-helper/hiter"
)

// Example_reduceGroup demonstrates grouping and aggregation
func Example_reduceGroup() {
	// Group by key and sum values
	type data struct {
		Group       string
		Value       int
		OtherFields []any
	}
	pairs := hiter.Divide(
		func(d data) (string, int) { return d.Group, d.Value },
		slices.Values(
			[]data{
				{"fruit", 10, nil},
				{"vegetable", 20, nil},
				{"fruit", 30, nil},
				{"fruit", 15, nil},
				{"vegetable", 25, nil},
			},
		),
	)

	grouped := hiter.ReduceGroup(
		func(acc, val int) int { return acc + val },
		0,
		pairs,
	)
	fmt.Println("Grouped sums:", grouped)

	// Output:
	// Grouped sums: map[fruit:55 vegetable:45]
}