“…The aim of this paper is to demonstrate that, beside superposition operators and the scalar play and stop considered in [6,7], there is a further large class of operators arising in optimal control applications that are Newton differentiable when endowed with a suitable (and computable) set-valued derivative, namely, solution mappings of obstacle-type variational inequalities (VIs) with unilateral constraints. Such functions arise, for instance, when optimal control problems governed by partial differential equations (PDEs) with H 1 -controls are studied, see sections 5 and 6, or in the field of optimal control of contact problems, see [19,27]. The main idea of our analysis is to exploit that solution maps of obstacle-type VIs possess pointwise-a.e.…”