An expression is a non-productive rule that resolves by calculation into a value. They consist of at least one operand, and additional operands may be linked via non-unary operators. An operand may be
- a literal value of any type,
- a variable or constant referred to by its identifier, or
- a function call.
Examples of expressions are:
x + 5
Expressions, and parts thereof, can be classified by their result type. Usually primarily arithmetic and logic expressions are distinguished. An arithmetic expression results in a numeric value. A logic expression results in a Boolean value.