Specifying a type
Type specifiers are used both for variables as for methods. It
consists of a primitive type specifier with optional
modifiers. A primitive type specifier either specifies a primitive type
or a node in the class hierarchy. In the latter case, any instance that
is a member of the specified class or
one of its subclasses passes the type test.
Type specifiers are no true objects in PCE, but special types similar
to integers, names, etc. The PCE type conversion system converts names
to types as required.
The specifiers for primitive types are:
int Integer
bool Boolean
name equivalent to `atom`
atom atom
type a type specifier
The modifiers are:
[<type>] Specified type or @default
<type>* Specified type or @nil
<type>? Specified type, obtainer or @arg1...@arg10
