fluffos/docs/lpc/constructs/if.md

title
constructs / if

if

The if else statement

LPC's if statement is identical to that provided by C. Syntax is as follows:

if (expression)
    statement;

Alternately:

if (expression) {
    statements;
}

Alternately:

if (expression0) {
    statements;
} else {
    statements1;
}

Alternately:

if (expression0) {
    statements0;
} else if (expression1) {
    statements1;
}

The number of else clauses is not explicitly limited.

---

Another favorite programming construct is the ? : operator, which also operates identical to C. The syntax is:

expression0 ? expression1_if_true : expression2_if_false

In some cases, ? : is an shorter way of expression constructs such as:

if (expression0)
    var = expression1;
else
    var = expression2;

which can be equivalently translated to:

var = expression0 ? expression1 : expression;

---

Nullish coalescing operator (??)

LPC also supports expr_left ?? expr_right, which returns expr_left when it is defined and evaluates/returns expr_right only when the left-hand side is undefined (see undefinedp() for what counts as undefined). It short-circuits like ||, but falsy values such as 0, 0.0, "", or ({ }) do not trigger the fallback.

int timeout = cfg["timeout"] ?? 60;          // use default only if key is undefined
string name = player->query_name() ?? "guest";  // RHS runs only when call returns undefined

Operator precedence sits between ?: and ||, mirroring the common pattern lookup ?? fallback without extra parentheses. Use || when you want to treat all falsy values as missing; use ?? when only truly undefined values should fall back.

Logical assignment operators (||=, &&=, ??=)

Short-circuit evaluation is also available in assignment form:

int connected = 0;
object sock = find_connection();

connected ||= open_default();       // assign only if connected is falsy
sock &&= reconnect(sock);           // assign only if sock is truthy
config["timeout"] ??= 60;           // assign only when key is undefined

||= evaluates the right-hand side only when the left-hand side is falsy (0 or 0.0). &&= does the reverse, running the right-hand side only when the left is truthy. ??= mirrors ??: the right-hand side runs only when the left-hand side is truly undefined (useful for lazily populating mappings). The lvalue is evaluated just once in every case.