Stateful Goroutines in Standard ML

(* In this example, we'll use modules to manage state and simulate
   concurrent operations. Standard ML doesn't have built-in concurrency
   primitives like goroutines, so we'll use a simplified approach. *)

structure StateManager = struct
    (* Our state will be a simple key-value store *)
    val state = ref (IntRedBlackMap.empty)

    (* Function to read from the state *)
    fun read key =
        case IntRedBlackMap.find(!state, key) of
            SOME value => value
          | NONE => 0  (* Default value if key not found *)

    (* Function to write to the state *)
    fun write (key, value) =
        state := IntRedBlackMap.insert(!state, key, value)
end

(* Simulating read and write operations *)
fun simulateOps () =
    let
        val readOps = ref 0
        val writeOps = ref 0
        
        (* Simulate read operations *)
        fun doReads 0 = ()
          | doReads n =
            let
                val key = Random.randRange (0, 4) (Random.rand (0, 0))
                val _ = StateManager.read key
                val _ = readOps := !readOps + 1
            in
                doReads (n - 1)
            end

        (* Simulate write operations *)
        fun doWrites 0 = ()
          | doWrites n =
            let
                val key = Random.randRange (0, 4) (Random.rand (0, 0))
                val value = Random.randRange (0, 99) (Random.rand (0, 0))
                val _ = StateManager.write (key, value)
                val _ = writeOps := !writeOps + 1
            in
                doWrites (n - 1)
            end
    in
        (* Start read and write operations *)
        doReads 1000;
        doWrites 100;
        
        (* Print results *)
        print ("readOps: " ^ Int.toString (!readOps) ^ "\n");
        print ("writeOps: " ^ Int.toString (!writeOps) ^ "\n")
    end

(* Main function *)
fun main () =
    (
        Random.rand (0, 0);  (* Initialize random seed *)
        simulateOps ()
    )

(* Run the main function *)
val _ = main ()

This Standard ML code simulates the stateful operations from the original Go example. Here’s a breakdown of the translation:

We define a StateManager structure to encapsulate the state and operations on it. This replaces the goroutine-based approach in Go.
The state is implemented as a reference to an IntRedBlackMap, which is a built-in map type in Standard ML.
read and write functions are defined within the StateManager to interact with the state.
The simulateOps function simulates concurrent read and write operations. It uses recursive functions doReads and doWrites to perform multiple operations.
We use mutable references readOps and writeOps to keep track of the number of operations performed.
The Random module is used to generate random numbers for keys and values.
The main function initializes the random seed and calls simulateOps.

To run this program, you would typically save it in a file (e.g., stateful_operations.sml) and use an Standard ML compiler or interpreter. For example, with the MLton compiler:

$ mlton stateful_operations.sml
$ ./stateful_operations
readOps: 1000
writeOps: 100

This Standard ML version provides a similar functionality to the Go example, demonstrating state management and simulated concurrent operations. However, it’s important to note that Standard ML doesn’t have built-in concurrency primitives like Go’s goroutines, so this is a simplified simulation of concurrent behavior.

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Stateful Goroutines in Standard ML