A calculus for assignments in higher-order languages
Matthias Felleisen, Daniel P. Friedman · 1987
Imperative assignments are abstractions of recurring programming patterns in purely functional programming languages. When added to higher-order functional languages, they provide a higher-level of modularity and security but invalidate the simple substitution semantics. We show that, given an operational interpretation of a denotational semantics for such a language, it is possible to design a two-level extension of the lu-calculus. This calculus provides a location-free rewriting semantics of the language and offers new possibilities for reasoning with assignments. The upper level of the calculus factors out all the steps in a reduction sequence which must be in a linear order; the lower level allows a partial ordering of reduction steps.