Compiling Exceptions Correctly

An exception compilation scheme that dynamically creates and removes exception handler entries on the stack. A formalization of an article of the same name by Hutton and Wright [1]. 1 Compiling exception handling theory Exceptions imports Main begin 1.1 The source language datatype expr = Val int | Add expr expr | Throw | Catch expr expr consts eval :: "expr ⇒ int option" primrec "eval (Val i) = Some i" "eval (Add x y) = (case eval x of None ⇒ None | Some i ⇒ (case eval y of None ⇒ None | Some j ⇒ Some(i+j)))" "eval Throw = None" "eval (Catch x h) = (case eval x of None ⇒ eval h | Some i ⇒ Some i)" 1.2 The target language datatype instr = Push int | ADD | THROW | Mark nat | Unmark | Label nat | Jump nat datatype item = VAL int | HAN nat types code = "instr list" stack = "item list" consts exec2 :: "bool * code * stack ⇒ stack"