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Programming Challenge: Launch 4 threads, goroutines, coroutines, or whatever your language uses for concurrency, in addition to the main thread. In the first 3, add numbers together (see sample code below) and pass the results to the 4th thread. That 4th thread should receive the 3 results, add the numbers together, format the results as a strin…
// Steve Phillips / elimisteve
// 2013.01.03
package main
import "fmt"
// intDoubler doubles the given int, then sends it through the given channel
func intDoubler(ch chan int, n int) {
ch <- n*2
func main() {
// Make channel of ints
ch := make(chan int)
answer := make(chan string)
// Spawn 3 goroutines (basically threads) to process data in background
go intDoubler(ch, 10)
go intDoubler(ch, 20)
go func(a, b int) { ch <- a+b }(30, 40) // Take 2 ints, write sum to `ch`
// Create anonymous function on the fly, launch as goroutine!
go func() {
// Save the 3 values passed through the channel as x, y, and z
x, y, z := <-ch, <-ch, <-ch
// Calculate answer, write to `answer` channel
answer <- fmt.Sprintf("%d + %d + %d = %d", x, y, z, x+y+z)
// Print answer resulting from channel read
fmt.Printf("%s\n", <-answer)
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timhuff commented Sep 28, 2015

Rust 1.3 solution (looks like the earlier Rust solutions are outdated)

use std::thread;

fn main() {
    let mut children = vec![];
    children.push(thread::spawn(move || {10*2}));
    children.push(thread::spawn(move || {20*2}));
    children.push(thread::spawn(move || {30+40}));

    let adder = thread::spawn(move || {
        let mut sum = 0;
        let result = children.into_iter().map(|child| {
            let value = child.join().unwrap();
            sum += value;
            format!("{}", value)
        }).collect::<Vec<_>>().join(" + ");
        return format!("{} = {}", result, sum);

    let result = adder.join().unwrap();
    println!("{}", result);

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Zizaco commented Jan 12, 2016

@polonskiy Actually, I'm not even mad! That's amazing 😨

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elimisteve commented Mar 12, 2017

Would be interesting to see this done with !

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