package main
import (
"fmt"
)
// Build a slice using a simple for‑loop.
// This is the most common and flexible approach.
func makeRangeLoop(start, end int) []int {
size := end - start
values := make([]int, size) // allocate exact size
for i := 0; i < size; i++ {
values[i] = start + i
}
return values
}
// Build a slice using append.
// Useful when you want dynamic growth or additional logic.
func makeRangeAppend(start, end int) []int {
values := []int{}
for n := start; n < end; n++ {
values = append(values, n)
}
return values
}
// Build a slice using a generator‑style channel.
// This allows streaming values lazily.
func makeRangeChannel(start, end int) []int {
ch := make(chan int)
// Produce values in a separate goroutine.
go func() {
for n := start; n < end; n++ {
ch <- n
}
close(ch)
}()
// Collect values.
values := []int{}
for v := range ch {
values = append(values, v)
}
return values
}
// Build a slice using copy into a pre‑allocated buffer.
// Shows how to repurpose an existing slice.
func makeRangeCopy(start, end int) []int {
size := end - start
values := make([]int, size)
for i := range values {
values[i] = start + i
}
return values
}
// Print a slice for demonstration.
func show(label string, values []int) {
fmt.Printf("%s: %v\n", label, values)
}
func main() {
a := makeRangeLoop(1, 10)
b := makeRangeAppend(1, 10)
c := makeRangeChannel(1, 10)
d := makeRangeCopy(1, 10)
show("loop", a)
show("append", b)
show("channel", c)
show("copy", d)
}
/*
run:
loop: [1 2 3 4 5 6 7 8 9]
append: [1 2 3 4 5 6 7 8 9]
channel: [1 2 3 4 5 6 7 8 9]
copy: [1 2 3 4 5 6 7 8 9]
*/
