instance_variable_get

/*
 *  call-seq:
 *     obj.instance_variable_get(symbol)    => obj
 *
 *  Returns the value of the given instance variable, or nil if the
 *  instance variable is not set. The <code>@</code> part of the
 *  variable name should be included for regular instance
 *  variables. Throws a <code>NameError</code> exception if the
 *  supplied symbol is not valid as an instance variable name.
 *     
 *     class Fred
 *       def initialize(p1, p2)
 *         @a, @b = p1, p2
 *       end
 *     end
 *     fred = Fred.new('cat', 99)
 *     fred.instance_variable_get(:@a)    #=> "cat"
 *     fred.instance_variable_get("@b")   #=> 99
 */

static VALUE
rb_obj_ivar_get(obj, iv)
    VALUE obj, iv;
{
    ID id = rb_to_id(iv);

    if (!rb_is_instance_id(id)) {
        rb_name_error(id, "`%s' is not allowed as an instance variable name", rb_id2name(id));
    }
    return rb_ivar_get(obj, id);
}