一段代码的疑问

Function.prototype.method = function(name, func) {
    this.prototype[name] = func;
    return this;
};

// A (rather complex) function that allows you to gracefully inherit
// functions from other objects and be able to still call the  'parent'
// object's function
Function.method('inherits', function(parent) {
    // Keep track of how many parent-levels deep we are
    var depth = 0;

    // Inherit the parent's methods
    var proto = this.prototype = new parent();

    // Create a new 'priveledged' function called 'uber', that when called
    // executes any function that has been written over in the inheritance
    this.method('uber', function uber(name) {

        var func; // The function to be execute
        var ret; // The return value of the function
        var v = parent.prototype; // The parent's prototype

        // If we're already within another 'uber' function
        if (depth) {
            // Go the necessary depth to find the orignal prototype
            for ( var i = d; i > 0; i += 1 ) {
                v = v.constructor.prototype;
            }

            // and get the function from that prototype
            func = v[name];

        // Otherwise, this is the first 'uber' call
        } else {
            // Get the function to execute from the prototype
            func = proto[name];

            // If the function was a part of this prototype
            if ( func == this[name] ) {
                // Go to the parent's prototype instead
                func = v[name];
            }
        }

        // Keep track of how 'deep' we are in the inheritance stack
        depth += 1;

        // Call the function to execute with all the arguments but the first
        // (which holds the name of the function that we're executing)
        ret = func.apply(this, Array.prototype.slice.apply(arguments, [1]));

        // Reset the stack depth
        depth -= 1;

        // Return the return value of the execute function
        return ret;
    });

    return this;
});

  for ( var i = d; i > 0; i += 1 ) {
                v = v.constructor.prototype;
            }