Expression Returns

// Example: Expression-Based Returns in Neuro
// Demonstrates implicit returns: a function body whose final expression is its
// value, with no `return` keyword.
//
// Every function below is called and printed, so the feature is visible in the
// program's output as well as in its exit code.

// Simple expression-based return
func double(x: i32) -> i32 {
    x * 2
}

// Expression-based return with statements before
func calculate(a: i32, b: i32) -> i32 {
    val sum: i32 = a + b
    val product: i32 = a * b
    sum + product
}

// Comparison expression as return
func is_positive(x: i32) -> bool {
    x > 0
}

// Logical expression as return
func both_positive(a: i32, b: i32) -> bool {
    a > 0 && b > 0
}

// Function call as expression return
func quad(x: i32) -> i32 {
    double(double(x))
}

// Main entry point
func main() -> i32 {
    val result1: i32 = double(5)
    val result2: i32 = calculate(3, 4)
    val result3: i32 = quad(2)

    println("double(5)             = {result1}")
    println("calculate(3, 4)       = {result2}")
    println("quad(2)               = {result3}")

    // A `bool` renders in a hole just as a number does.
    val positive: bool = is_positive(result1)
    val both: bool = both_positive(result2, result3)
    println("is_positive(10)       = {positive}")
    println("both_positive(19, 8)  = {both}")

    val total: i32 = result1 + result2 + result3
    println("total                 = {total}")

    total
}