Control Flow

if / else

if is an expression — it produces a value:

let status = if score >= 90 { "excellent" } else { "keep going" };

For side effects, use it as a statement:

if temperature > 100 {
    println("Warning: overheating!");
} else if temperature > 80 {
    println("Running warm.");
} else {
    println("All good.");
}

No parentheses around the condition. Braces are always required.

Loops

while

let mut count = 0;
while count < 10 {
    println(count);
    count = count + 1;
}

for loops

for iterates over anything iterable:

let names = ["Alice", "Bob", "Charlie"];
for name in names {
    println(f"Hello, {name}!");
}

With ranges:

// 0, 1, 2, 3, 4
for i in 0..5 {
    println(i);
}

// 0, 1, 2, 3, 4, 5 (inclusive)
for i in 0..=5 {
    println(i);
}

loop

An infinite loop. Use break to exit:

let mut attempt = 0;
let result = loop {
    attempt = attempt + 1;
    if try_connect() {
        break "connected";
    }
    if attempt >= 3 {
        break "failed";
    }
};

loop is an expression — break value sets the value of the whole loop.

break and continue

for i in 0..100 {
    if i % 2 == 0 {
        continue;    // skip even numbers
    }
    if i > 10 {
        break;       // stop after 10
    }
    println(i);      // prints 1, 3, 5, 7, 9
}

match

Pattern matching is one of the most powerful tools in Kāra. At its simplest, it's a better switch:

let day = 3;
let name = match day {
    1 => "Monday",
    2 => "Tuesday",
    3 => "Wednesday",
    4 => "Thursday",
    5 => "Friday",
    6 | 7 => "Weekend",
    _ => "Invalid",
};

But match goes far beyond this — it works with enums, structs, nested data, and guards. We'll cover it fully in Chapter 6.

The pipe operator

Kāra has a pipe operator |> for chaining function calls left-to-right:

let result = data
    |> transform
    |> validate
    |> save;

This is equivalent to save(validate(transform(data))) but reads in the order things happen. It's especially useful for data processing pipelines.