Strong Reduction for Typed Lambda Calculus with First-Class Environments

Programs contain variables, and the bindings of these variables to the corresponding values are kept in a so-called 'environment'. A first-class environment is a mechanism that the environments in programs can be treated as first-class entities, which are objects that can to be passed and returned between functions and procedures. Nishizaki proposed the lambda calculus with first-class environments, called the environment lambda calculus, and has investigated its theoretical properties [6---8, 10]. The various systems of the environment lambda calculus are based on weak reduction, that is, application of a substitution to a lambda abstraction is postponed until an argument is applied to it. In this paper, we propose a simply-typed lambda calculus with strong reduction. We investigate several theoretical properties such as the subject reduction theorem.