golang 1.8泛型测试

golang 目前最新版本是1.8.1， 泛型功能测试一把。

golang.org 官方例子 main.go内容如下:

package main

import (
  "fmt"
)

type Number interface {
  int64 | float64
}

func main() {
  // Initialize a map for the integer values
  ints := map[string]int64{
    "first":  34,
    "second": 12,
  }

  // Initialize a map for the float values
  floats := map[string]float64{
    "first":  35.98,
    "second": 26.99,
  }

  fmt.Printf("Non-Generic Sums: %v and %v\n",
    SumInts(ints),
    SumFloats(floats))

  fmt.Printf("Generic Sums: %v and %v\n",
    SumIntsOrFloats[string, int64](ints),
    SumIntsOrFloats[string, float64](floats))

  fmt.Printf("Generic Sums, type parameters inferred: %v and %v\n",
    SumIntsOrFloats(ints),
    SumIntsOrFloats(floats))

  fmt.Printf("Generic Sums with Constraint: %v and %v\n",
    SumNumbers(ints),
    SumNumbers(floats))

}

// SumInts adds together the values of m.
func SumInts(m map[string]int64) int64 {
  var s int64
  for _, v := range m {
    s += v
  }
  return s
}

// SumFloats adds together the values of m.
func SumFloats(m map[string]float64) float64 {
  var s float64
  for _, v := range m {
    s += v
  }
  return s
}

// SumIntsOrFloats sums the values of map m. It supports both floats and integers
// as map values.
func SumIntsOrFloats[K comparable, V int64 | float64](m map[K]V) V {
  var s V
  for _, v := range m {
    s += v
  }
  return s
}

// SumNumbers sums the values of map m. Its supports both integers
// and floats as map values.
func SumNumbers[K comparable, V Number](m map[K]V) V {
  var s V
  for _, v := range m {
    s += v
  }
  return s
}

测试：

root@jack-VirtualBox:/tmp/test# ./test 
Non-Generic Sums: 46 and 62.97
Generic Sums: 46 and 62.97
Generic Sums, type parameters inferred: 46 and 62.97
Generic Sums with Constraint: 46 and 62.97
root@jack-VirtualBox:/tmp/test#

与c++的泛型的定义比较，不同之处：
golang的泛型放在[]种，c++的泛型放在<>中。