Boolean expression

In computer science, a Boolean expression is an expression in a programming language that produces a Boolean value when evaluated, i.e. one of 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 > 3" is evaluated as true.
  • The expression "3 > 5" is evaluated as false.
  • "5>=3" and "3<=5" are equivalent Boolean expressions, both of which are evaluated as true.
  • "typeof true" returns "boolean" and "typeof false" returns "boolean"
  • Of course, most Boolean expressions will contain at least one variable (X > 3), and often more (X > Y).

See also

References

  1. ↑ 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 .
  2. ↑ van Melkebeek, Dieter (2000), Randomness and Completeness in Computational Complexity, Lecture Notes in Computer Science, 1950, Springer, p. 22, ISBN 9783540414926 .
  3. ↑ E.g. for Java see Brogden, William B.; Green, Marcus (2003), Java 2 Programmer, Que Publishing, p. 45, ISBN 9780789728616 .
  • The Calculus of Logic, by George Boole, Cambridge and Dublin Mathematical Journal Vol. III (1848), pp. 183–98.
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