(10 13 concatenation and parsing, or list structure manipulators, are chosen as a function of a particular source language and a particular target machine. RABBIT deals only with fundamental environment and control issues common to most modes of algorithmic expression. while syntactic issues tend to be rather superficial, we point out that algebraic syntax tends to obscure the fundamental nature of function calling and tail-recursion by arbitrarily dividing functions into syntactic classes such as "operators" and "functions". ([Standish], for example, uses much space to exhibit each conceptually singular transformation in a multiplicity of syntactic manifestations.) The lack of an "anonymous" notation for functions in most algebraic languages, and the inability to treat functions as data objects, is a distinct disadvantage. The uniformity of LISP syntax makes these issues easier to deal with. To the LISP community in particular we address these additional points: (11 (12) Lexical scoping need not be as expensive as is commonly thought. Experience with lexically-scoped interpreters is misleading; lexical scoping is not inherently slower than dynamic scoping. While some implementations may entail access through multiple levels? of structure, this occurs only under circumstances (accessing of variables through multiple levels of closure) which could not even be expressed in a dynamically scoped language. Unlike deep-bound dynamic variables, compiled lexical access requires no search; unlike shallow-bound dynamic variables, lexical binding does not require that values be put in a canonical value cell. The compiler has complete discretion over the manipulation of environments and variable values. The "display" technique used in Algol implementations can be generalized to provide an efficient solution to the FUNARG problem. Lexical scoping does not necessarily make LISP programming unduly difficult.
