This is an implementation of a switch operator for PostScript programs that replicates the switch...case syntax seen in many other programming languages, such as C.
The switch...case construct (which goes by a variety of names) generally has the following elements:
- The switch is entered with a singular value, here called the comparand, to be compared to other values. (In C, the value must be an integer, but other languages may allow comparing values of any type.)
- The switch contains zero or more cases, each corresponding to a value, and will execute one or more code branches depending on the value chosen. (Some languages restrict the switch to executing exactly one code branch; C bases it on
goto-like labels, and consequently has a "fall-through" mechanic where execution continues past subsequent labels if not explicitly broken with abreakstatement.) - The switch may have a "default" case containing code to be executed if no other case matches.
This implementation has the following elements:
- The comparand can be of any type except
arraytype. This means arrays and procs cannot be used as comparands. - The switch will execute exactly one of the supplied procs unless no case value matches the comparand and no default was supplied.
- A default case may be supplied using a value of
null.