Expressions

An expression is a piece of code that produces a value. Expressions can use integer literals, variable names, function calls, and operators:

var width = 10
var height = 20
var area = width * height

In the last line, width * height is an expression. Matchbox evaluates it and uses the resulting value to initialize area.

Integer Literals

An integer written directly in source code is an expression:

var answer = 42
var mask = 0b1111
var color = 0xFF00

See Integer Literals for the supported notations and digit separators.

Variable Names

A variable name can be used as an expression after the variable has received a value:

var subtotal = 40
var total = subtotal + 2

Here, subtotal produces the value stored in that variable.

Operators

Operators combine or transform values:

var sum = 10 + 20
var area = 6 * 7
var remainder = 17 % 5
var negative = -sum

See Operators for the complete list of arithmetic, bitwise, assignment, and unary operators, including their precedence and edge cases.

Function Calls

A call to a function that returns a value can be used as an expression:

var larger = max(10, 20)
var distance = abs(-12)

The arguments passed to a function are expressions too. Expressions can therefore be nested:

var limited = clamp(abs(-120), 0, 100)

Parentheses

Use parentheses to group part of an expression and make the intended evaluation order clear:

var result = (10 + 20) * 3

Without the parentheses, multiplication and addition may be evaluated in a different order.

Matchbox evaluates binary operands from left to right. Binary operators at the same precedence level are left-associative in 0.2.

Expressions and Statements

An expression produces a value, while a statement performs an action. For example, the right side of an assignment is an expression, but the complete assignment is a statement:

var total = 0
total = 10 + 20

Function calls can also be used as statements when their result does not need to be stored:

print(total)

Next Step

Continue to Functions.