A system is said to be reactive if it interacts continuously with an environment, at a speed imposed by the environment. The system deals with inputs and outputs and the languages for programming reactive systems aim at describing the complex ordering and causality relations between the inputs and the corresponding outputs. The synchronous approach, based upon the assumption that a system reacts in zero time, allows the definition of compositional semantics for various kinds of language constructs, in data-flow frameworks as well as in imperative frameworks. We take advantage of this compositionality property to define the mixing of data-flow constructs with automaton compositions in a single language. We apply the results to Lustre and Argos, and discuss some implementation issues.< >