Conditional Statements

Conditional statements let you execute different blocks of code depending on whether a condition evaluates to true or false. Conditions must evaluate to a bool value.

if (condition) {
    // executes if condition is true
} else {
    // executes if condition is false
}

if (condition1) {
    // executes if condition1 is true
} else if (condition2) {
    // executes if condition1 is false but condition2 is true
} else {
    // executes if all previous conditions are false
}

Looping Constructs

A for loop allows repeating a block of code multiple times. It usually consists of three optional parts inside the loop header:

• Initializer - runs once before the loop begins (often used to declare and initialize a counter).
• Condition - checked before each iteration; if false, the loop exits.
• Increment/Update - executed after each iteration.

for (initializer; condition; increment) {
    // body
}

Classic Counter Loop

for (var i = 0; i < 10; i++) {
    // executes 10 times: i = 0..9
}

Manual Increment Loop

for (var i = 0; i < 10;) {
    // executes while i < 10
    // you must manually increment i inside the body
    i++;
}

Here, the increment part is omitted. The loop continues until the condition becomes false, but you control when i is updated.

Conditionless Loop with Initializer

for (var i = 0;) {
    // infinite unless you break manually
    // no condition, no increment
    if (i > 5) {
        break; // stop after 6 iterations
    }
    i++;
}

Only the initializer is given. Since there's no condition, the loop is infinite unless explicitly terminated with break or return.

Pure Infinite loop

for {
    // infinite loop with no initializer, no condition, no increment
    // must be exited with break or return
}

While Statement

A while loop repeatedly executes a block of code as long as a condition evaluates to true. The condition is checked before each iteration. If the condition is false at the start, the loop body never runs.

while (condition) {
    // body
}

#i = 0;

while (true) {
    printf("v: %d\n", i);
    i++;

    if (i == 10) {
        break; // exit when i reaches 10.
    }
}

Switch Statement

A switch statement allows execution to branch based on the value of an expression. It provides a concise way to compare against multiple possibilities without writing a long chain of if–else if statements.

⚠️ Note: This is not pattern matching. Cases in Cyrus are always compared against raw values, not structural patterns or conditions.

Basic Form

#i: int = 0;

switch (i) {
    case 0:
        // This block runs if i is equal to 0.
        break;

    case 1:
        // This block runs if i is equal to 1.
        break;

    default:
        // This block runs if none of the above cases match.
        break;
}

Fallthrough behavior

In Cyrus, switch statements automatically fall through to the next case unless you explicitly use break. This is the same behavior as in C and C++, and unlike languages such as Go or Rust where each case ends automatically.

#i: int = 2;

switch (i) {
    case 2:
        // Runs when i == 2
        // Execution continues into the next case unless we break.
    case 3:
        // This also runs, because there was no break after case 2.
        break;
}

Enum Variants

Switch statements can also match enum variants, but that will be explained in detail in the future on the Enums page.