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:
“I say you must not win an unjust case by oaths.”
—Aeschylus (525–456 B.C.)
“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)
“The true critic is a scrupulous avoider of formulae; he refrains from statements which pretend to be literally true; he finds fact nowhere and approximation always.”
—T.S. (Thomas Stearns)