Types can be used in four places:
 
 Declaring type of global variables.
 Declaring type of functions.
 Declaring type of arguments to functions.
 Declaring type of local variables in functions.
 
Normally, the type information is completely ignored, and can be regarded 
purely as documentation. However, when the basic type of a function is 
declared, then a more strict type checking will be enforced inside of that 
function.  That means that the type of all arguments must be defined, and the 
variables can only be used to store values of the declared type.  The 
function call_other() is defined to return an unknown type, as the compiler 
has no way of knowing the return type.  This value must be casted (when 
strict type checking is enabled).  Casting a type is done by putting the type 
name inside a pair of '(' and ')'.
 
An example when querying the short description of an object:
 
  (string)call_other(ob, "short");
  ...or...
  (string)ob->short();
 
When a function is compiled with strict type testing, it can only call other
functions that are already defined.  If they are not yet defined, prototypes 
must be used to allow the current function to call them.
 
An example of a prototype:
 
  string func(int arg);
 
Note the ';' instead of a body to the function.  All arguments must be given
by names, but do not have to have the same names as in the real definition. 
All types must of course be the same.
 
There are two kinds of types.  Basic types, and special types.  There can be 
at most one basic type, but any number of special types assigned to a 
variable/function.
 
The strict type checking is only used by the compiler, not at runtime.  So,
it is actually possible to store a number in a string variable even when 
strict type checking is enabled.
 
Why use strict type checking?  It is really recommended, because the compiler
will find many errors at compile time, which will save a lot of hard work. It
is in general much harder to trace an error occuring at run time. 
 
The basic types can be divided into groups.  Those that are referenced by 
value, and those that are referenced by address.  The types int, string,
and float are referenced by value.  The types mapping, function, object, 
and pointers ('<type> *') are referenced by address.  If a value of this type 
is assigned to a variable or passed as argument, they will all point to the 
same actual data.  That means that if the value of an element in an array is 
changed, then it can modify all other variables pointing to the same array. 
Changing the size of the array will always allocate a new one though. The 
comparison operator, ==, will compare the actual value for the group of 
value-referenced types above.  But for arrays, mappings, etc, it will simply 
check if it is the same array, mapping, etc. That has the very important 
implication that the expression ({}) == ({}) will evaluate to false because
the array construction operator-pair, ({}) always generates a new array.
 
Basic types
 
int
 An integer number (32 bit).
 
float
 A floating point number (32 bit).
 
string
 An unlimited string of characters. 
 
object
 A pointer to an object.  
 
mapping
 A form of associative array, see separate documentation.
 
function
 A special type that points to (object, function name) pairs, see
 separate documentation.
 
Arrays
 Arrays are declared using a '*' following a basic type.  For example, 
 declaring an array of numbers: int *arr;.  Use the type mixed if you want an 
 array of arrays, or a mixed combination of types.
 
void
 This type is only usable for functions.  It means that the function will not
 return any value.  The compiler will complain (when type checking is enabled)
 if a return value is used.
 
mixed
 This type is special, in that it is valid to use in any context.  Thus, if 
 everything was declared mixed, then the compiler would never complain. This 
 is of course not the idea. It is really only supposed to be used when a 
 variable really is going to contain different types of values. This should
 be avoided if possible.  It is not good coding practice to allow a function,
 for example, to return different types.
 
Special types
 
There are some special types, which can be given before the basic type. These
special types can also be combined.  When using special type T before an 
inherit statement, all symbols defined by inheritance will also get the 
special type T.  The only special case is public--defined symbols, which can 
not be redefined as private in a private inheritance statement.
 
varargs
 A function of this type can be called with a variable number of arguments.
 Otherwise, the number of arguments is checked, and can generate an error.
 
private
 Can be given for both functions and variables. Functions that are private in
 object A can not be called through call_other() in another object.  They're
 also not accessable to any object that inherits A.
 
static
 This special type behaves different for variables and functions.  It is 
 similar to private for functions, in that they cannot be called from other 
 objects with call_other().  static variables will be neither saved nor 
 restored when using save_object() or restore_object().
 
public
 A function defined as public will always be accessible from other objects, 
 even if private inheritance is used.
 
nomask
 All symbols defined as nomask cannot be redefined by inheritance.  They can 
 still be used and accessed as usual.  nomask also blocks functions from
 being shadowed with shadow().