Operators

Arithmetic

Operator	Operation
+	Addition, or string concatenation when both operands are strings
-	Subtraction
*	Multiplication or repetition
/	Division
%	Remainder
^	Power

OSL evaluates mixed arithmetic operators from left to right. It does not apply the usual multiplication-before-addition rule.

number wrong = 10 + 2 * 3
number right = 10 + (2 * 3)

The first expression is (10 + 2) * 3. The compiler warns about unparenthesized mixed arithmetic. Parenthesize the intended grouping, especially for time, sizes, and persisted values.

Integer overflow raises an error. A divisor that the compiler knows is zero is a compile error.

Concatenation and merge

++ converts operands to strings when used with scalar values. It merges arrays or objects when both sides are collections.

string label = "count: " ++ count
int[] values = [1, 2] ++ [3]
object options = defaults ++ overrides

Comparison

Operator	Meaning
==, !=	Loose equality and inequality
===, !==	Strict equality and inequality
<, <=, >, >=	Ordering
in, !in	Membership
of	Membership alias in expressions, position iteration in loops

Loose string equality is case-insensitive and may coerce values. Use === when case and runtime type matter.

Boolean and nullish operators

boolean valid = ready and !failed
any selected = primary ?? fallback

and and or return according to OSL truthiness and short-circuit. ?? only falls back for null. ??= assigns only when the current value is null.

Logical operators have precedence rules, with and binding more tightly than or. The compiler warns when different logical operators are mixed without parentheses. Parenthesize the intended grouping when an expression uses both.

Ranges and the ternary form

start to end creates an inclusive integer range in either direction.

int[] forward = 1 to 3
int[] backward = 3 to 1

The ternary form has no colon:

string label = ready ? "ready" "waiting"

Pipe and bitwise operators

|> sends the left value to a one-argument function:

log 10 |> double |> format

Bitwise operators are &, |, ^^, <<, and >>.

Regular-expression literals

Prefix a backtick string with $ to create a regular expression. Flags follow the closing backtick:

auto digits = $`\d+`
log digits.test("item-42")
log $`hello`i.test("HELLO")