[Grace-core] Class Encoding

[Eric Mullen]

I'm currently working for Professor Bruce on implementing an
interpreter for Grace, and I was wondering about peoples' thoughts on
a class encoding inspired by and closely based on Andrew Black's
(https://projects.cecs.pdx.edu:8443/~black/NewOOL/index.cgi/wiki/ClassesObjectAndConstructors)
but with some slight modifications.

The following code:

class a {(n:Number) ->
    var x:Number := n
}

class b {(m:Number) ->
    extends a.new(m+1)
    var y:Number := m
}

would be rewritten as:

object a {
    method _allocate() {
        //returns uninitialized object skeleton
        object obj {
            var x:Number := Uninitialized
        }
        obj
    }
    method _new(obj,n) {
        obj := Any._new(obj)
        obj.x:=(n)
        obj
    }
    method new(n) {
        _new(_allocate(),n)
    }
}

object b {
    method _allocate() {
        //returns uninitialized object skeleton
        //has all fields of both class b and all super classes (that
weren't overridden)
        object obj {
            var x:Number := Uninitialized
            var y:Number := Uninitialized
        }
        obj
    }
    method _new(obj,m) {
        obj := a._new(obj,m+1)
        obj.y:=(m)
        obj
    }
    method new(m) {
        _new(_allocate(),m)
    }
}

This allows for classes to be implemented within the language, while
still allowing concatenation (as opposed to delegation) as the method
for inheritance (http://portal.acm.org/citation.cfm?id=219264, cited
by Andrew Black on the wiki).