icioo(1)icioo(1)NAMEicioo - ICI object-oriented programming
DESCRIPTION
<I>This page is out of date. A whole new OO mechanism has been avail‐
able since ICI 3.0.</I>
Ici's support for object-oriented programming is very simple. Inheri‐
tance 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 identi‐
fier, 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 facili‐
ties.
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