2.1 Conditionals

From this point on in your code, the compiler knows the symbol Symbol. Symbols are, like the Pascal language, case insensitive.

You can also dene a symbol on the command line. the -dSymbol option denes the symbol Symbol. You can specify as many symbols on the command line as you want.

Undening an existing symbol is done in a similar way:

If the symbol didn't exist yet, this doesn't do anything. If the symbol existed previously, the symbol will be erased, and will not be recognized any more in the code following the {$undef ...} statement.

You can also undene symbols from the command line with the -u command-line switch.

To compile code conditionally, depending on whether a symbol is dened or not, you can enclose the code in a {$ifdef Symbol} ...{$endif} pair. For instance the following code will never be compiled:

Similarly, you can enclose your code in a {$ifndef Symbol} ...{$endif} pair. Then the code between the pair will only be compiled when the used symbol doesn't exist. For example, in the following example, the call to the DoSomething will always be compiled:

You can combine the two alternatives in one structure, namely as follows

In this example, if MySymbol exists, then the call to DoSomething will be compiled. If it doesn't exist, the call to DoSomethingElse is compiled.