Abstract

We present a type-based ow analysis for simply typed lambda calculus with booleans, data-structures and recursion. The analysis is exact in the following sense: if the analysis predicts a redex, then there exists a reduction sequence (using standard reduction plus context propagation rules) such that this redex will be reduced. The precision is accomplished using intersection typing. It follows that the analysis is non-elementary recursive | more surprisingly, the analysis is decidable. We argue that the specication of such an analysis provides a good starting point for developing new ow analyses and an important benchmark against which other ow analyses can be compared. Furthermore, we believe that the techniques employed for stating and proving exactness are of independent interest: they provide methods for reasoning about the precision of program analyses. 1

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