and demonstrated that the usual view of function calls as pushing a return address must lead to an either inefficient or inconsistent implementation, while the tail-recursive approach of SCHEME leads to a uniform discipline in which function calls are treated as GOTO statements which also pass arguments. We also noted that a consequence of lexical scoping is that the only code which can reference the value of a variable in a given environment is code which is closed in that environment or which receives the value as an argument; this in turn implies that a compiler can structure a run-time environment in any arbitrary fashion, because it will compile all the code which can reference that environment, and so can arrange for that code to reference it in the appropriate manner. Such references do not require any kind of search (as is commonly and incorrectly believed in the LISP community because of early experience with LISP interpreters which search a-lists) because the compiler can determine the precise location of each variable in an environment at compile time. It is not necessary to use a standard format, because neither interpreted code nor other compiled code can refer to that environment. (This is to be constrasted with "spaghetti stacks" [Bobrow and Wegbreit].) In [Declarative] we also carried on the analysis of continuation-passing style, and noted that transforming a program into this style elucidates traditional compilation issues such as register allocation because user variables and intermediate quantities alike are made manifest as variables on an equal footing. Appendix A of [Declarative] contained an algorithm for converting any SCHEME program (not containing ASET) to continuation-passing style.
We have implemented two compilers for the language SCHEME. The purpose was to explore compilation techniques for a language modelled on lambda-calculus, using lambda-calculus-style models of imperative programming constructs. Both compilers use the strategy of converting the source program to continuation--
