If my memory serves me well and if I am properly reminded of the preprocessor that I used with C/C++ long ago, then what I'm about to ask is probably not what's the case with {$define}. I will put it forth anyway

In the FPC Compiler Reference it says that this can be used to define a symbol. Also, in the FPC Programmer's Guide it says that "The directive {$DEFINE name} defines the symbol name. This symbol remains defined until the end of the current module (i.e. unit or program), or until a $UNDEF name directive is encountered."

Of course, I would think that therefore I could do something like this: it's possible to assign my own symbols for use in the language. For example, it is possible to choose ~ as a symbol for not, and that the compiler will actually know and treat ~ as not. This seems to be entailed by the description that I read.

For instance, maybe I could try something like
Code:
{$define ~ not}
or
Code:
{$define ~ = not}
or some such thing?

Of course, I tested it and it doesn't work. Is it at all even possible to do such a thing?

If {$define} is used for defining some sort of difficult formula, then how exactly should this thing be used? Can you give an example?