channel.nula

// Channel.nula — a single-value channel actor (stdlib pattern)
// Provides put(value) and take() behaviors.
// Multiple puts before a take overwrite the stored value.
//
// This is the simplest channel pattern, modelled on Erlang's
// "process as mailbox" idiom.  A multi-value buffered channel
// would use an array buffer with the same put/take interface;
// bounded backpressure (sender suspension on full) requires
// VM-level mailbox capacity support.

actor Channel {
    state value = nil
    state has_value = false

    // Put a value into the channel.  Overwrites any unread value.
    behavior put(v) {
        self.value = v
        self.has_value = true
    }

    // Take the stored value.  Returns nil if nothing was put.
    behavior take() {
        if self.has_value then {
            self.has_value = false
            self.value
        } else {
            nil
        }
    }

    // True when a value is waiting to be taken.
    behavior is_full() {
        self.has_value
    }
}