M provides two primary means for values to come into existence: computed values and stored values (aka fields). Computed and stored values may occur with both module and entity declarations and are scoped by their container.
A computed value is derived from evaluating an expression. In contrast, a field stores a value and the contents of the field may change over time. 
A ComputedValueDeclaration binds a name to an expression that is used to compute the resultant value.
ComputedValueDeclaration: Identifier FormalParameters ReturnTypeopt ExpressionBody FormalParameters: ( Parametersopt ) Parameters: Parameter Parameters , Parameter Parameter: Identifier TypeAscriptionopt ReturnType: ...