Skip to main content

Control Flow

Control flow statements determine the execution path of your program. In Kyna, all conditions must be parenthesized and all code blocks must use curly braces {}.

1. Branching with if, else if, and else​

Conditions evaluate to a boolean expression:

fn evaluateHealth(statusCode: int): str {
    if (statusCode >= 200 && statusCode < 300) {
        return "Healthy";
    } else if (statusCode >= 500) {
        return "Server Error";
    } else {
        return "Degraded";
    }
}

print(evaluateHealth(200)); # Healthy
print(evaluateHealth(503)); # Server Error

2. Pattern Matching with switch​

The switch statement matches a value against distinct case arms.

Key characteristics:

  • No Implicit Fall-Through: Only the matching arm executes.
  • Braces Required: Each arm body is scoped within {}.
  • Default Arm: Catch-all branch when no previous cases match.
fn getMethodDescription(method: str): str {
    switch (method) {
        case "GET": {
            return "Read resource";
        }
        case "POST": {
            return "Create resource";
        }
        case "PUT": {
            return "Replace resource";
        }
        case "DELETE": {
            return "Remove resource";
        }
        default: {
            return "Unsupported HTTP method";
        }
    }
}

print(getMethodDescription("POST")); # Create resource

3. Iteration: while Loops​

The while loop runs as long as its condition remains true:

var retries = 3;

while (retries > 0) {
    print("Retrying connection... attempts left:", retries);
    retries = retries - 1;
}

print("Connection aborted.");

4. Iteration: Structured loop​

Kyna's loop statement provides a classic three-clause for-loop syntax: loop (init; condition; increment):

var totalSum = 0;

loop (var i = 1; i <= 5; i = i + 1) {
    totalSum = totalSum + i;
}

print("Sum 1..5:", totalSum); # 15

5. Loop Control: break and continue​

  • break: Immediately exits the loop.
  • continue: Skips the remainder of the current iteration and begins the next.
loop (var i = 0; i < 10; i = i + 1) {
    if (i % 2 == 0) {
        continue; # Skip even numbers
    }
    if (i > 7) {
        break;    # Stop early
    }
    print("Odd number:", i);
}

Output:

Odd number: 1
Odd number: 3
Odd number: 5
Odd number: 7

Next Steps​