icioo(1)

NAME
icioo - ICI object-oriented programming

DESCRIPTION
<I>This page is out of date. A whole new OO mechanism has been available since ICI 3.0.</I>

Ici's support for object-oriented programming is very simple. Inheritance is already provided through the ability to extend one structure's scope by defining a super structure for it. This can be done either with the notation:
    static my_instance = [struct:my_parent x, y ]; or with the functional notation
    static my_instance = super(my_parent, x, y); although it's probably better to set up an atomic (`class') variable for the super structure, and use that:
    @my_parent to refer to an atomic (unchanging) version of your `class' struct.

The method call is achieved by an extension of the normal function call operator "()". When the "()" operand is a function identifier, the function is called in the usual way with the supplied parameter list. But if the "()" operand is a pointer object keyed by a function identifier, the function is called with the object pointed-to passed as an implicit first parameter.

The binary operator `@' forms such a pointer from an aggregate object (usually a struct) and an identifier (i.e. a member of the struct). This is the same basic technique used for dynamic dispatch in languages like Smalltalk and Objective-C.

Here is a little example showing a few ways this can be used. Note the occasional use of literal functions.
static
showtype(any, label)
{
    printf("%s is a %s\n", label, typeof(any));
}
/*
 * Class definition.
 */
static Point =
[struct
    p_x     = 0.0,
    p_y     = 0.0,
    p_swap  = [func (self) { self.p_x <=> self.p_y; } ],
    p_print = [func (s) { printf("Pt <%g %g>\n", s.p_x, s.p_y);} ],
    p_what  = showtype,
];
static p1 = struct(@Point);  /* Set super struct to be atomic Point */
    p1.p_x = 1.2;
    p1.p_y = 3.4;
    p1@p_what("p1");
    p1@p_print();
    p1@p_swap();
    p1@p_print();

Which produces this output when run:
p1 is a struct
Pt <1.2 3.4>
Pt <3.4 1.2>

In summary, method calls depend on:

•   Ici's super linkage to provide the normal OO inheritance name search mechanism.

•   The `@' binary operator to form a keyed pointer that will select the named member of the struct.

•   The "()" (call) operator's special treatment of a function-keyed pointer.

The syntax is the natural result of using ici's normal language facilities.