In computer science, a Boolean expression is an expression used in programming languages that produces a Boolean value when evaluated. A Boolean value is either true or false. A Boolean expression may be composed of a combination of the Boolean constants true or false, Boolean-typed variables, Boolean-valued operators, and Boolean-valued functions.[1]
Boolean expressions correspond to propositional formulas in logic and are a special case of Boolean circuits.[2]
Boolean operators
Most programming languages have the Boolean operators OR, AND and NOT; in C and some newer languages, these are represented by "||" (double pipe character), "&&" (double ampersand) and "!" (exclamation point) respectively, while the corresponding bitwise operations are represented by "|", "&" and "~" (tilde).[3] In the mathematical literature the symbols used are often "+" (plus), "·" (dot) and overbar, or "∨" (cup), "∧" (cap) and "¬" or "′" (prime).
Examples
- The expression
5 > 3is evaluated as true. - The expression
3 > 5is evaluated as false. 5>=3and3<=5are equivalent Boolean expressions, both of which are evaluated as true.typeof trueandtypeof falsereturn boolean- Of course, most Boolean expressions will contain at least one variable (
X > 3), and often more (X > Y).
See also
- Expression (computer science)
- Expression (mathematics)
References
- ^ Gries, David; Schneider, Fred B. (1993), "Chapter 2. Boolean Expressions", A Logical Approach to Discrete Math, Monographs in Computer Science, Springer, p. 25ff, ISBN 9780387941158.
- ^ van Melkebeek, Dieter (2000), Randomness and Completeness in Computational Complexity, Lecture Notes in Computer Science, 1950, Springer, p. 22, ISBN 9783540414926.
- ^ E.g. for Java see Brogden, William B.; Green, Marcus (2003), Java 2 Programmer, Que Publishing, p. 45, ISBN 9780789728616.
External links
- The Calculus of Logic, by George Boole, Cambridge and Dublin Mathematical Journal Vol. III (1848), pp. 183–98.