Case and Switch Statements
Switch statements (in some languages, case statements or multiway branches) compare a given value with specified constants and take action according to the first constant to match. There is usually a provision for a default action ('else','otherwise') to be taken if no match succeeds. Switch statements can allow compiler optimizations, such as lookup tables. In dynamic languages, the cases may not be limited to constant expressions, and might extend to pattern matching, as in the shell script example on the right, where the '*)' implements the default case as a regular expression matching any string.
| Pascal: | C: | Java: | Shell script: |
|---|---|---|---|
| case someChar of 'a': actionOnA; 'x': actionOnX; 'y','z':actionOnYandZ; else actionOnNoMatch; end; | switch (someChar) { case 'a': actionOnA; break; case 'x': actionOnX; break; case 'y': case 'z': actionOnYandZ; break; default: actionOnNoMatch; } | switch (age) { case 1: System.out.printf("You're one."); break; case 2: System.out.printf("You're two."); break; case 3: System.out.printf("You're three."); break; case 4: System.out.printf("You're four."); break; default: System.out.printf("You're neither!"); break; } | case $someChar in a) actionOnA; ;; x) actionOnX; ;; ) actionOnYandZ; ;; *) actionOnNoMatch ;; esac |
Read more about this topic: Conditional (computer Programming)
Famous quotes containing the words case, switch and/or statements:
“In the case of news, we should always wait for the sacrament of confirmation.”
—Voltaire [François Marie Arouet] (1694–1778)
“Uncritical semantics is the myth of a museum in which the exhibits are meanings and the words are labels. To switch languages is to change the labels.”
—Willard Van Orman Quine (b. 1908)
“Science is a system of statements based on direct experience, and controlled by experimental verification. Verification in science is not, however, of single statements but of the entire system or a sub-system of such statements.”
—Rudolf Carnap (1891–1970)