Instantiation

Instantiation is the mechanism of creating a new object of a given class; instantiation is done by using the class as a selector and by giving a list of "<slot> = <value>" pairs as arguments :

complex(re = 0.0, im = 1.0)  person(age = 0, father = john)

Recall that the list of instances of a given class is only kept for non-ephemeral classes (a class is ephemeral if has been declared as such or if it inherits from the ephemeral_object class). The creation of a new instance of a class yields to a function call to the method close. Objects with a name are represented by the class thing, hence descendents of thing (classes that inherit from thing) can be given a name with the definition operation ::. These named objects can later be accessed with their name, while objects with no name offer no handle to manipulate them after their creation outside of their block (objects with no name are usually attached to a local variable with a let whenever any other operation other than the creation itself is needed) :

paul :: person(age = 10, father = peter)

Notice that the identifier used as the name of an object is a constant that cannot be changed. Thus, it is different from creating a global variable that would contain an object as in :

aGoodGuy:person :: person(age = 10, father = peter)

Additionally, there is a simpler way of instantiating parameterized classes by dropping the slot names. All values of the parameter slots must be provided in the exact order that was used to declare the list of parameters. For instance, we could use :

complex(0.0,1.0), stack(integer)

The previously mentioned instantiation form only applies to a parameterized class. It is possible to instantiate a class that is given as a parameter (say, the variable v) using the new method. New(v) creates an instance of the class v and new(v,s) creates a named instance of the class v (assumed to be a subclass of thing) with the name s.