In computer science, a value is an expression which cannot be evaluated any further. {{#invoke:Footnotes|sfn}} The members of a type are the values of that type. {{#invoke:Footnotes|sfn}} For example, the expression “1 + 2” is not a value as it can be reduced to the expression “3”. This expression cannot be reduced any further (and is a member of the type Nat) and therefore is a value. The “value of a variable” is given by the corresponding mapping in the environment.