The control approaches based on the task function formalism, and particularly those structured as a prioritized hierarchy of tasks, enable to build complex behaviors with elegant properties of robustness and portability. However, it is difficult to consider a straightforward integration of tasks described by unilateral constraints in such frameworks. Indeed, unilateral constraints exhibit irregularities that prevent the insertion of unilateral tasks at any priority levels, other than the lowest, of a hierarchy. In this paper, we present an original method to generalize the hierarchy-based control schemes to account for unilateral constraints at any priority level. We develop our method first for task sequencing using only kinematic description; then we expand it to task description using the operational space formulation. The method applies in robotics and computer graphics animation. Its practical implementation is exemplified through a real manipulator and on a humanoid avatar by realizing a visual servoing task under the constraint of joint limits.