before-generic-example.go

func MaxInt(args ...int) int {
	if len(args) == 0 {
		return *new(int)
	}
	max := args[0]
	for _, arg := range args[1:] {
		if arg > max {
			max = arg
		}
	}
	return max
}

func MaxFloat(args ...float64) float64 {
	if len(args) == 0 {
		return *new(float64)
	}
	max := args[0]
	for _, arg := range args[1:] {
		if arg > max {
			max = arg
		}
	}
	return max
}

generic-example-minmax.go

package main

import (
	"fmt"

	"golang.org/x/exp/constraints"
)

func Max[T constraints.Ordered](args ...T) T {
	if len(args) == 0 {
		return *new(T)
	}
	max := args[0]
	for _, arg := range args[1:] {
		if arg > max {
			max = arg
		}
	}
	return max
}

func Min[T constraints.Ordered](args ...T) T {
	if len(args) == 0 {
		return *new(T)
	}
	min := args[0]
	for _, arg := range args[1:] {
		if arg < min {
			min = arg
		}
	}
	return min
}

generic-example-test.go

func TestMinInt(t *testing.T) {
	var tests = []struct {
		args []int
		want int
	}{
		{[]int{}, 0},
		{[]int{1}, 1},
		{[]int{1, 3, 2}, 1},
	}
	for _, test := range tests {
		if got := Min(test.args...); got != test.want {
			t.Errorf("Min(%v) = %v, want %v", test.args, got, test.want)
		}
	}
}

func TestMaxFloat64(t *testing.T) {
	var tests = []struct {
		args []float64
		want float64
	}{
		{[]float64{}, 0},
		{[]float64{1.0}, 1.0},
		{[]float64{1, 3.2, -2}, 3.2},
	}
	for _, test := range tests {
		if got := Max(test.args...); got != test.want {
			t.Errorf("Max(%v) = %v, want %v", test.args, got, test.want)
		}
	}
}

func TestMaxString(t *testing.T) {
	var tests = []struct {
		args []string
		want string
	}{
		{[]string{}, ""},
		{[]string{"a"}, "a"},
		{[]string{"a", "b", "c"}, "c"},
	}
	for _, test := range tests {
		if got := Max(test.args...); got != test.want {
			t.Errorf("Max(%v) = %v, want %v", test.args, got, test.want)
		}
	}
}