What is the correct way to record a single channel in Go?
I'm new to go.
I am trying to find a simple way to implement a pipe that only outputs individual values.
I want to do the following:
package example
import (
"fmt"
"testing"
)
func TestShouldReturnDistinctValues(t *testing.T) {
var c := make([]chan int)
c <- 1
c <- 1
c <- 2
c <- 2
c <- 3
for e := range c {
// only print 1, 2 and 3.
fmt.println(e)
}
}
Should I be worried about leaking memory here if I used the map to remember the previous values?
Thank.
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2 answers
You really can't do that, you need to keep track of the values somehow map[int]struct{}
, probably the most memory efficient.
Simple example :
func UniqueGen(min, max int) <-chan int {
m := make(map[int]struct{}, max-min)
ch := make(chan int)
go func() {
for i := 0; i < 1000; i++ {
v := min + rand.Intn(max)
if _, ok := m[v]; !ok {
ch <- v
m[v] = struct{}{}
}
}
close(ch)
}()
return ch
}
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I've done similar things before, except my problem was output inputs in ascending order. You can do this by adding a normal routine. Here's an example:
package main
func main() {
input, output := distinct()
go func() {
input <- 1
input <- 1
input <- 2
input <- 2
input <- 3
close(input)
}()
for i := range output {
println(i)
}
}
func distinct() (input chan int, output chan int) {
input = make(chan int)
output = make(chan int)
go func() {
set := make(map[int]struct{})
for i := range input {
if _, ok := set[i]; !ok {
set[i] = struct{}{}
output <- i
}
}
close(output)
}()
return
}
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