GDL resembles Lisp, but instead of defining functions,
the contents of a file declare
certain objects (such as units and unit types) to exist,
and specify values for their properties.
In other words, GDL is nonprocedural.
This means that most of the time, you can list the various
forms in any order you like.
The main restriction is that any symbol, such as a variable
or the name of a type, must be defined before it is used.
Also, forms such as set
and add
, that set the
value of a variable or property,
always overwrite the previous data irreversibly,
so ordering of these is very important.