I would like to know if the go language allows checking for multiple channels being ready at the same time.
Here is a somewhat contrived example of what I'm trying to do. (The actual reason is to see if I can implement petrinets natively in go)
package main
import "fmt"
func mynet(a, b, c, d <-chan int, res chan<- int) {
for {
select {
case v1, v2 := <-a, <-b:
res <- v1+v2
case v1, v2 := <-c, <-d:
res <- v1-v2
}
}
}
func main() {
a := make(chan int)
b := make(chan int)
c := make(chan int)
d := make(chan int)
res := make(chan int, 10)
go mynet(a, b, c, d, res)
a <- 5
c <- 5
d <- 7
b <- 7
fmt.Println(<-res)
fmt.Println(<-res)
}
This doesn't compile as shown. It can be made to compile by only checking one channel, but then it can trivially deadlock if that channel is ready but the other one is not.
package main
import "fmt"
func mynet(a, b, c, d <-chan int, res chan<- int) {
for {
select {
case v1 := <-a:
v2 := <-b
res <- v1+v2
case v1 := <-c:
v2 := <-d
res <- v1-v2
}
}
}
func main() {
a := make(chan int)
b := make(chan int)
c := make(chan int)
d := make(chan int)
res := make(chan int, 10)
go mynet(a, b, c, d, res)
a <- 5
c <- 5
d <- 7
//a <- 5
b <- 7
fmt.Println(<-res)
fmt.Println(<-res)
}
In the general case, I might have multiple cases waiting on the same channel, e.g.
case v1, v2 := <-a, <-b:
...
case v1, v2 := <-a, <-c:
...
so I can't commit to either branch when a value is ready on channel a: only when all values are ready.