// Demonstrating built-in effects in Lux
//
// Lux provides several built-in effects:
// - Console: print and read from terminal
// - Fail: early termination with error
// - State: get/put mutable state (requires runtime initialization)
// - Reader: read-only environment access (requires runtime initialization)
//
// This example demonstrates Console and Fail effects.
//
// Expected output:
// Starting computation...
// Step 1: validating input
// Step 2: processing
// Result: 42
// Done!

// A function that can fail
fn safeDivide(a: Int, b: Int): Int with {Fail} =
    if b == 0 then Fail.fail("Division by zero")
    else a / b

// A function that validates input
fn validatePositive(n: Int): Int with {Fail} =
    if n < 0 then Fail.fail("Negative number not allowed")
    else n

// A computation that uses multiple effects
fn compute(input: Int): Int with {Console, Fail} = {
    Console.print("Starting computation...")
    Console.print("Step 1: validating input")
    let validated = validatePositive(input)
    Console.print("Step 2: processing")
    let result = safeDivide(validated * 2, 1)
    Console.print("Result: " + toString(result))
    result
}

// Main function
fn main(): Unit with {Console} = {
    let result = run compute(21) with {}
    Console.print("Done!")
}

let output = run main() with {}