CASE Statement

CASE expr OF { "|" case ... } [ ELSE statements ] END
  where
    case = { label "," ... } "=>" statements
    label = const-expr [ ".." const-expr ]

The case statement is a specialization of the IF/THEN/ELSIF statement that allows discrimination among a set of possible values of some ordinal expression expr. If a case is encountered that is not handled by one of the arms of the case statement, the ELSE arm is taken; if no ELSE arm is present in this situation, a checked run-time error occurs.

The compiler will generate a warning if no ELSE arm appears and not all cases are covered. This can be ignored at risk of a possible runtime error, or an empty ELSE arm can be inserted to pacify the compiler and runtime system.

Example

CASE IO.GetChar() OF
| 'a'..'z' => IO.Put("Lowercase");
| 'A'..'Z' => IO.Put("Uppercase");
| '0'..'9' => IO.Put("Digit");
| '!', '.', ':', ';', '?' => IO.Put("Punctuation");
ELSE
  IO.Put("Other")
END