Control Flow & Branching Reference

Kyna provides structured constructs for branching, iterative loops, pattern matching, and error isolation.

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Conditionals: if, else if, else

Conditionals evaluate boolean expressions. In Kyna, conditional expressions do not require parentheses around the test expression, but braces { ... } around the execution blocks are always mandatory.

fn classifyStatus(code: int): str {
    if (code >= 200 && code < 300) {
        return "Success";
    } else if (code >= 400 && code < 500) {
        return "Client Error";
    } else if (code >= 500) {
        return "Server Error";
    } else {
        return "Informational or Redirect";
    }
}

Expression-Capable if

In Kyna, if can be evaluated as an expression producing a value:

const maxRetries = if (isProduction) 5 else 1;
print("Configured retries:", maxRetries);

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Switch Statements: switch / case

switch matches an expression against constant scalar values.

• Each case block must be enclosed in braces { ... }.
• Execution does not fall through between cases (no break keyword needed).
• An optional default case handles unmatched values.

fn getMimeType(extension: str): str {
    switch (extension) {
        case "json": {
            return "application/json";
        }
        case "html": {
            return "text/html";
        }
        case "png": {
            return "image/png";
        }
        default: {
            return "application/octet-stream";
        }
    }
}

print(getMimeType("json")); # "application/json"

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Pattern Matching: match

The match expression provides concise, declarative matching with the wildcard operator _:

fn describeHttpCode(status: int): str {
    return match (status) {
        200 => "OK";
        201 => "Created";
        400 => "Bad Request";
        401 => "Unauthorized";
        404 => "Not Found";
        500 => "Internal Server Error";
        _   => "Unknown Status Code";
    };
}

print(describeHttpCode(404)); # "Not Found"

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Loops: while and loop

Kyna supports two loop constructs: condition-driven while and 3-clause iterative loop.

while Loops

Executes as long as the boolean condition remains true:

var cursor = 0;
while (cursor < 5) {
    print("Cursor position:", cursor);
    cursor = cursor + 1;
}

3-Clause loop (C-style For Loop)

The loop (init; condition; step) construct allows clear index management:

var sum = 0;
loop (var i = 1; i <= 10; i = i + 1) {
    sum = sum + i;
}
print("Sum of 1 to 10:", sum); # 55

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Jump Statements: break and continue

• break: Immediately terminates the innermost loop.
• continue: Skips the remaining statements in the current iteration and evaluates the next loop cycle.

loop (var i = 0; i < 10; i = i + 1) {
    if (i % 2 == 0) {
        continue; # Skip even numbers
    }
    if (i > 7) {
        break;    # Stop loop after reaching 7
    }
    print("Odd number:", i); # Outputs 1, 3, 5, 7
}

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Labeled Loops

When working with nested iterations, you can attach labels to loops to break or continue an outer loop directly:

outer: loop (var row = 0; row < 5; row = row + 1) {
    inner: loop (var col = 0; col < 5; col = col + 1) {
        if (row == 2 && col == 2) {
            print("Found target at (2, 2). Terminating search.");
            break outer; # Breaks the outer loop directly
        }
    }
}