A New Formulation of the Catch/Throw Mechanism

The catch/throw mechanism in Common Lisp gives a simple control structure for non-local exits. Nakano[7, 9] and Sato[13] proposed intuitionistic calculi with inference rules which give logical interpretations of the catch/throw-constructs. Although the calculi are theoretically well-founded, we cannot use the catch/throw mechanism for handling run-time errors in a meaningful way, because of the side-condition of the implication-introduction rule (the formulation rule of the -abstract). This de ciency is critical if we use higher-order functions with the catch/throw mechanism. In this paper, we propose a new formulation of catch/throw calculi, which has no side-condition on the implication-introduction rule. By restricting the types of thrown terms to data types (non-functional types) instead, we obtain a strongly normalizing calculus for the catch/throw mechanism where we can write higher-order functions which handles run-time errors.