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/*-----------------------------------------------------------------------------
This trivial Elk extension demonstrates encapsulation of a C++ class in
a first-class Scheme type, and encapsulation of member functions in
Scheme primitives.
See constructor.c in this directory for compilation instructions.
Here is a transcript showing a test run under Solaris 2.4 using the
GNU g++ compiler:
% g++ -fpic -I/usr/elk/include -c class.c
%
% scheme
> (load 'class.o)
> (define x (make-foo))
x
> (read-val x)
1234
> (write-val! x 11)
> (read-val x)
11
> (exit)
%
-----------------------------------------------------------------------------*/
class foo {
int val;
public:
int read_val(void);
void write_val(int);
foo() { val = 1234; };
};
int foo::read_val(void) {
return val;
}
void foo::write_val(int newval) {
val = newval;
}
/* ---------------------------------- */
#include "scheme.h"
struct S_Foo {
Object tag; class foo foo;
};
int T_Foo;
#define FOO(x) ((struct S_Foo *)POINTER(x))
Object P_Make_Foo(void) {
Object f = Alloc_Object(sizeof (struct S_Foo), T_Foo, 0);
FOO(f)->foo.write_val(1234); /* FOO(f)->foo.foo() is not allowed?! */
return f;
}
Object P_Read_Val(Object x) {
Check_Type(x, T_Foo);
return Make_Integer(FOO(x)->foo.read_val());
}
Object P_Write_Val(Object x, Object y) {
Check_Type(x, T_Foo);
FOO(x)->foo.write_val(Get_Integer(y));
return Void;
}
Foo_Print(Object h, Object port, int raw, int depth, int length) {
Printf(port, "#[foo %d]", FOO(h)->foo.read_val());
}
int Foo_Equal(Object x, Object y) {
return FOO(x)->foo.read_val() == FOO(y)->foo.read_val();
}
void elk_init_foo() {
T_Foo = Define_Type(0, "foo", NOFUNC, sizeof(struct S_Foo),
Foo_Equal, Foo_Equal, Foo_Print, NOFUNC);
Define_Primitive((Object(*)(...))P_Make_Foo, "make-foo", 0, 0, EVAL);
Define_Primitive((Object(*)(...))P_Read_Val, "read-val", 1, 1, EVAL);
Define_Primitive((Object(*)(...))P_Write_Val, "write-val!", 2, 2, EVAL);
}
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