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channel

Channels provide a safe way for concurrent goroutines to communicate with each other in Soul. They allow you to send and receive values between different parts of your concurrent program, preventing race conditions and ensuring thread-safe data sharing.

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Creating Channels

Channels are created using the Concurrency.createChannel() function: 
// Unbuffered channel (synchronous)
ch = Concurrency.createChannel()

// Buffered channel with capacity of 5
bufferedCh = Concurrency.createChannel(5)

// Buffered channel with capacity of 10
largeCh = Concurrency.createChannel(10)

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Channel Send Operations

Send values to channels using the <- operator or the send() method: 
ch = Concurrency.createChannel(3)

// Send using arrow syntax
ch <- "hello"
ch <- 42
ch <- true

// Send using method syntax
ch.send("world")
ch.send(100)

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Channel Receive Operations

Receive values from channels using the <- operator or the receive() method: 
ch = Concurrency.createChannel()

// Send a value in another goroutine
Concurrency.run(soul() {
    ch <- "message from goroutine"
})

// Receive using arrow syntax
message = <-ch
println("Received: " + message)

// Receive using method syntax
value = ch.receive()
println("Received: " + value)

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Buffered vs Unbuffered Channels

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Unbuffered Channels (Synchronous)

// Unbuffered channel - blocks until receiver is ready
ch = Concurrency.createChannel()

Concurrency.run(soul() {
    ch <- "sync message"  // Blocks until someone receives
})

message = <-ch  // Blocks until someone sends
println(message)

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Buffered Channels (Asynchronous)

// Buffered channel - doesn't block until buffer is full
ch = Concurrency.createChannel(2)

ch <- "message 1"  // Doesn't block
ch <- "message 2"  // Doesn't block
// ch <- "message 3"  // Would block since buffer is full

msg1 = <-ch  // "message 1"
msg2 = <-ch  // "message 2"

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Select Statements

Select statements allow you to work with multiple channel operations: 
ch1 = Concurrency.createChannel()
ch2 = Concurrency.createChannel()

// Send to channels in separate goroutines
Concurrency.run(soul() {
    Concurrency.sleep(100)
    ch1 <- "from channel 1"
})

Concurrency.run(soul() {
    Concurrency.sleep(200)
    ch2 <- "from channel 2"
})

// Wait for the first available channel
select {
    case msg1 = <-ch1:
        println("Received from ch1: " + msg1)
    case msg2 = <-ch2:
        println("Received from ch2: " + msg2)
}

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Channel Patterns

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Producer-Consumer Pattern

soul producer(ch) {
    for (i = 0; i < 5; i++) {
        ch <- "item " + i
        println("Produced: item " + i)
        Concurrency.sleep(100)
    }
    ch.close()
}

soul consumer(ch) {
    while (!ch.isClosed()) {
        item = <-ch
        println("Consumed: " + item)
    }
}

// Usage
ch = Concurrency.createChannel(2)
Concurrency.run(producer, ch)
Concurrency.run(consumer, ch)

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Fan-Out Pattern

soul fanOut(input, output1, output2) {
    for (value in input) {
        // Send to both output channels
        output1 <- value
        output2 <- value
    }
}

input = Concurrency.createChannel()
output1 = Concurrency.createChannel()
output2 = Concurrency.createChannel()

Concurrency.run(fanOut, input, output1, output2)

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Worker Pool Pattern

soul worker(id, jobs, results) {
    for (job in jobs) {
        println("Worker " + id + " processing job " + job)
        Concurrency.sleep(100)  // Simulate work
        results <- "Result from worker " + id + " for job " + job
    }
}

soul genesis() {
    jobs = Concurrency.createChannel(5)
    results = Concurrency.createChannel(5)
    
    // Start 3 workers
    for (i = 1; i <= 3; i++) {
        Concurrency.run(worker, i, jobs, results)
    }
    
    // Send jobs
    for (j = 1; j <= 5; j++) {
        jobs <- j
    }
    jobs.close()
    
    // Collect results
    for (r = 1; r <= 5; r++) {
        result = <-results
        println(result)
    }
}

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Channel Methods

Channels support several useful methods: 
ch = Concurrency.createChannel(5)

// Send and receive
ch.send("hello")
message = ch.receive()

// Check channel state
println("Length: " + ch.length())    // Current buffer size
println("Capacity: " + ch.capacity()) // Maximum buffer size
println("Closed: " + ch.isClosed())   // Whether channel is closed

// Close channel
ch.close()

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Channel with Select and Timeout

ch = Concurrency.createChannel()
timeout = Concurrency.createChannel()

// Set up timeout
Concurrency.run(soul() {
    Concurrency.sleep(1000)  // 1 second timeout
    timeout <- true
})

// Wait for either data or timeout
select {
    case data = <-ch:
        println("Received data: " + data)
    case <-timeout:
        println("Operation timed out")
}

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Best Practices

  1. Close channels when done: Always close channels when no more data will be sent
  2. Use buffered channels for async: When you don’t need synchronous communication
  3. Use select for multiple channels: Don’t block on single channel operations
  4. Handle channel closure: Check if channels are closed before sending
// Good - proper channel usage
soul channelExample() {
    ch = Concurrency.createChannel(3)
    
    // Producer
    Concurrency.run(soul() {
        for (i = 0; i < 5; i++) {
            ch <- "data " + i
        }
        ch.close()  // Important: close when done
    })
    
    // Consumer
    while (!ch.isClosed()) {
        select {
            case data = <-ch:
                println("Processing: " + data)
            default:
                Concurrency.sleep(10)  // Prevent busy waiting
        }
    }
}
Channels are fundamental to Soul’s concurrency model, providing a safe and efficient way to coordinate between concurrent operations.