Generic Prepend in Go!

genericprepend.go

package main

// https://play.golang.com/p/PNax2a1rL3q

import (
	"fmt"
	"math/rand"
	"time"

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

type Number interface {
	constraints.Signed | constraints.Unsigned | constraints.Float
}

func prepend[T Number](list []T, elems ...T) []T {
	results := make([]T, len(list)+len(elems))
	results = append(results, 0)
	copy(results[len(elems):], list)
	copy(results[:len(elems)], elems)
	return results
}

func intPrepend(list []int, elems ...int) []int {
	results := make([]int, len(list)+len(elems))
	results = append(results, 0)
	copy(results[len(elems):], list)
	//results[0] = elem
	copy(results[:len(elems)], elems)
	return results
}


func main() {
	rand.Seed(time.Now().Unix())

	var items []int
	items = rand.Perm(10)
	fmt.Println(items)
	results := prepend(items, 1000, 2000)
	items2 := []float32{10.0, 200.0, 200}
	results2 := prepend(items2, 10000.0)
	fmt.Println(results, results2)
}