go_generics_tutorial_sum_function_with_type_constraints.go

1package main
2
3import "fmt"
4
5type Number interface {
6	int64 | float64
7}
8
9func main() {
10	// Initialize a map for the integer values
11	ints := map[string]int64{
12		"first":  34,
13		"second": 12,
14	}
15
16	// Initialize a map for the float values
17	floats := map[string]float64{
18		"first":  35.98,
19		"second": 26.99,
20	}
21
22	fmt.Printf("Non-Generic Sums: %v and %v\n",
23		SumInts(ints),
24		SumFloats(floats))
25
26	fmt.Printf("Generic Sums: %v and %v\n",
27		SumIntsOrFloats[string, int64](ints),
28		SumIntsOrFloats[string, float64](floats))
29
30	fmt.Printf("Generic Sums, type parameters inferred: %v and %v\n",
31		SumIntsOrFloats(ints),
32		SumIntsOrFloats(floats))
33
34	fmt.Printf("Generic Sums with Constraint: %v and %v\n",
35		SumNumbers(ints),
36		SumNumbers(floats))
37}
38
39// SumInts adds together the values of m.
40func SumInts(m map[string]int64) int64 {
41	var s int64
42	for _, v := range m {
43		s += v
44	}
45	return s
46}
47
48// SumFloats adds together the values of m.
49func SumFloats(m map[string]float64) float64 {
50	var s float64
51	for _, v := range m {
52		s += v
53	}
54	return s
55}
56
57// SumIntsOrFloats sums the values of map m. It supports both int64 and float64
58// as types for map values.
59func SumIntsOrFloats[K comparable, V int64 | float64](m map[K]V) V {
60	var s V
61	for _, v := range m {
62		s += v
63	}
64	return s
65}
66
67// SumNumbers sums the values of map m. It supports both integers and floats
68// as map values.
69func SumNumbers[K comparable, V Number](m map[K]V) V {
70	var s V
71	for _, v := range m {
72		s += v
73	}
74	return s
75}