Control Flow

This note covers conditionals, loops, and assertions in Compact.

Docs: Compact Reference

Intuition First

Control flow in Compact is constrained by design. No recursion, bounded loops only.

if (condition) {
  // then branch
} else {
  // else branch
}

if (value > 0) {
  result = true;
}

// wrong - not allowed
if (x == 1) { } else if (x == 2) { }

// correct
if (x == 1) { } else { if (x == 2) { } }

assert(condition, "error message");
assert(value > 0, "Must be positive");

for (const item of collection) {
  // process item
}

Bound must be compile-time known.

const sum = v.fold((acc, x) => acc + x, 0);

While loops are not allowed.

Not allowed. Use fold instead:

// wrong
for (const x of v) { if (x == target) return true; }

// correct
return v.fold((found, x) => found || x == target, false, v);

const found = v.fold((acc, x) => acc || x == target, false, v);

const total = v.fold((sum, x) => sum + x, 0n);

const max = v.fold((m, x) => x > m ? x : m, default<Field>());