Inside Delphi 2006 (Wordware Delphi Developers Library)

Just like the if-then statement, the case statement can have the else section to cover any condition not tested before. The syntax of the case-else statement is:

case expression of case_1: statement_1; case_n: statement_n; else else_statement; end;

The else section can also have its own block:

case expression of case_1: statement_1; case_n: statement_n; else begin else_statement; end; end;

The syntax requirements of the else keyword are different in the if-then-else and case-else statements. In the if-then-else statement, the semicolon is not allowed before the else keyword, while in the case-else statement it is.

Listing 3-14: The case-else statement

var x: Integer; begin ReadLn(x); case x of 1: WriteLn('Gold'); 2: WriteLn('Silver'); 3: WriteLn('Bronze'); else WriteLn('No medal for you.'); end; ReadLn; end.

You can also nest case statements and, if you do so carefully, you can increase the speed of your application even further. We can modify the application that displays the names of the months by using two case statements. The outer case statement checks if the number is in the 1 to 12 range, and the inner case statement displays month names. This solution is displayed in Listing 3-15.

Listing 3-15: Nested case statements

program Project1; {$APPTYPE CONSOLE} uses SysUtils; var monthNum: Integer; begin Write('Enter a number from 1 to 12: '); ReadLn(monthNum); case monthNum of 1..12: begin case monthNum of 1: WriteLn('January'); 2: WriteLn('February'); 3: WriteLn('March'); 4: WriteLn('April'); 5: WriteLn('May'); 6: WriteLn('June'); 7: WriteLn('July'); 8: WriteLn('August'); 9: WriteLn('September'); 10: WriteLn('October'); 11: WriteLn('November'); 12: WriteLn('December'); end; // inner case end; // 1..12 else WriteLn(monthNum, ' is not a valid number.'); end; // outer case ReadLn; end.