An expression in a programming language is a combination of values, variables, operators, and functions that are interpreted (evaluated) according to the particular rules of precedence and of association for a particular programming language, which computes and then produces (returns, in a stateful environment) another value. The expression is said to evaluate to that value. As in math, the expression is (or can be said to have) its evaluated value; the expression is a representation of that value. So, in mathematics, an expression is a representation of a value.
Expressions may or may not have side effects. An expression with side effects does not normally have the property of referential transparency. In many languages (e.g. C++) statements may be ended with a semicolon ';' to turn the expression into an expression statement. This asks the implementation to evaluate the expression for its side-effects only, and disregard the result of the expression.
See also
References
- Expression in The Free On-line Dictionary of Computing, Editor Denis Howe.