About

An Expression is a suite of special token that:

• are contained in statements
• and produce value (evaluate)

ie:

• It's a piece of language that can be evaluated/executed.
• Evaluating an expression produces a value
• The content of a language script file is an expression.

They are a value specifications that specify values resulting from a computation.

The expression execution order is determined by control-flow statements like if and for.

An expression is any reference to a variable or value, or a set of variable( s) and value( s) combined with operators.

Component

The following token compose an expression:

• constants
• literal
• variable
• operator
• function

List

• Variable expression
• Mathematics Expression
• …

• expression statement: a general expression that stands alone, generally it's used as a call expression statement to call a Function.

Example

a = b * 2; 

This statement has four expressions in it:

• 2 is a literal value expression.
• b is a variable expression, which means to retrieve its current value.
• b * 2 is an arithmetic expression, which means to do the multiplication.
• a = b * 2 is an assignment expression, which means to assign the result of the b * 2 expression to the variable a.

Documentation / Reference

• wiki/Expression_(computer_science)
• Unified Modeling Language (UML) - 2.5.1 - chapter 8.3