Abstract

We define an extension of the call-by-name lambda calculus with additional constructs and reduction rules that represent mutable variables and assignments. The extended calculus has neither a concept of an explicit store nor a concept of evaluation order; nevertheless, we show that programs in the calculus can be implemented using a single-threaded store. We also show that the new calculus has the Church-Rosser property and that it is a conservative extension of classical lambda calculus with respect to operational equivalence; that is, all algebraic laws of the functional subset are preserved. 1 Introduction Are assignments harmful? Common wisdom in the functional programming community has it that they are: seemingly, they destroy referential transparency, they require a determinate evaluation order, and they weaken otherwise powerful type systems such as ML's. Consequently, programming languages with a strong functional orientation often forbid or at least discourage the use of assi...

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