We present a destruction-aware type system for the functional language Safe, which is a first-order eager language with facilities for programmer controlled destruction and copying of data structures. It provides also regions, i.e. disjoint parts of the heap, where the program allocates data structures. The runtime system does not need a garbage collector and all allocation/deallocation actions are done in constant time.The language is equipped with several analyses and inference algorithms so that regions, sharing information and types are automatically inferred by the compiler. Here, we concentrate on the correctness of the type system with respect to the operational semantics of the language. In particular, we prove that, in spite of sharing and of the use of implicit and explicit memory deallocation operations, all well-typed programs will be free of dangling pointers at runtime.The paper ends up with some examples of well-typed programs.

The parallel-functional language Eden has a non-deterministic construct, the process abstraction merge, which interleaves a set of input lists to produce a single non-deterministic list. Its non-deterministic behaviour is a consequence of its reactivity: it immediately copies to the output list any value appearing at any of the input lists. This feature is essential in reactive systems and very useful in some deterministic parallel algorithms. The presence of non-determinism creates some problems such that some internal transformations in the compiler must be disallowed. The paper describes several non-determinism analyses developed for Eden aimed at detecting the parts of the program that, even in the presence of a process merge, still exhibit a deterministic behaviour. A polynomial cost algorithm which annotates Eden expressions is described in detail. A denotational semantics is described for Eden and the correctness of all the analyses is proved with respect to this semantics.

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Abstract. Safe is a first-order eager language with facilities for programmer-controlled destruction and copying of data structures. It provides also regions, i.e. disjoint parts of the heap where the programmer may allocate data structures. A type system is used to avoid dangling pointers arising from the inadequate usage of these facilities. In this paper we present an inference algorithm, we describe its implementation, and give a number of successfully typed examples. Also the correctness of the algorithm is proved.