docs / guide / The Cajeta Guide

12 — Control flow

The grammar is C-family. Conditions are parenthesized; bodies use braces. Run the examples: ControlFlowDemo and SwitchTernaryDemo.

if / else, while, do

int32 evenSum = 0;
int32 oddSum  = 0;
int32 i = 1;
while (i <= 5) {
    if (i % 2 == 0) {
        evenSum = evenSum + i;
    } else {
        oddSum = oddSum + i;
    }
    i = i + 1;
}

int32 n = 0;
do {
    n = n + 1;        // body runs at least once
} while (n < 3);

for and enhanced-for

int32 fact = 1;
for (int32 k = 1; k <= 5; k = k + 1) {
    fact = fact * k;
}

int32[] xs = [1, 2, 3, 4];
int32 sqSum = 0;
for (int32 x : xs) {          // x is a per-iteration borrow
    sqSum = sqSum + x * x;
}

break and continue

Both work unlabeled and labeled; a labeled break exits the named loop.

int32 sum = 0;
for (int32 i = 0; i < 10; i = i + 1) {
    if (i == 5) { break; }
    if (i % 2 == 0) { continue; }
    sum = sum + i;
}

outer: for (int32 a = 0; a < 3; a = a + 1) {
    for (int32 b = 0; b < 3; b = b + 1) {
        if (a + b == 3) { break outer; }
    }
}

switch — statement and expression

The classic statement form falls through unless you break; stacked labels (case 2: case 3:) share one arm.

int32 day = 3;
int32 out = 0;
switch (day) {
    case 1:
        out = 10;
        break;
    case 2: case 3:       // multi-label fall-through
        out = 23;
        break;
    default:
        out = 99;
        break;
}

The arrow form is an expression: each arm is a single expression, there is no fall-through, and the whole switch can be assigned, returned, or embedded.

int32 code = 2;
int32 r = switch (code) {
    case 1 -> 100;
    case 2, 3 -> 200;     // multi-label arm
    default -> -1;
};
int32 sum = 1000 + switch (code) {
    case 2 -> 7;
    default -> 0;
};

Ternary and instanceof

cond ? a : b evaluates only the selected branch; mixed-type branches widen to the larger type (int32 vs float64 below).

int32 a = 5;
int32 b = 10;
int32 min = a < b ? a : b;
float64 mixed = a < b ? 1.5 : 2;      // widens to float64

boolean isInt = a instanceof int32;
String tag = mixed instanceof float64 ? "f64" : "other";

instanceof currently matches against the operand’s static type; it does not yet walk the runtime class hierarchy for class types.

Next: Strings & formatting.

Source: docs/guide/12-control-flow.md · 1 min · 146 words