Lisp is the world's greatest programming language---or so its proponents think. The structure of Lisp makes it easy to extend the language or even to implement entirely new dialects without starting from scratch. Overall, the evolution of Lisp has been guided more by institutional rivalry, one-upsmanship, and the glee born of technical cleverness that is characteristic of the "hacker culture" than by sober assessments of technical requirements. Nevertheless this process has eventually produced both an industrialstrength programming language, messy but powerful, and a technically pure dialect, small but powerful, that is suitable for use by programming-language theoreticians. We pick up where McCarthy's paper in the first HOPL conference left off. We trace the development chronologically from the era of the PDP-6, through the heyday of Interlisp and MacLisp, past the ascension and decline of special purpose Lisp machines, to the present era of standardization activities. We then examine...

Accumulators are proposed as a new type of high-level iteration construct for imperative languages. Accumulators are user-programmed mechanisms for successively combining a sequence of values into a single result value. The accumulated result can either be a simple numeric value such as the sum of a series or a data structure such as a list. Accumulators naturally complement constructs that allow iteration through user-programmed sequences of values such as the iterators of CLU and the generators of Alphard. A practical design for high-level iteration is illustrated by way of an extension to Modula-2 called Modula Plus. The extension incorporates both a redesigned mechanism for iterators as well as the accumulator design. Several applications are illustrated including both numeric and data structure accumulation. It is shown that the design supports efficient iteration both because it is amenable to implementation via in-line coding and because it allows high-level iteration concepts to be implemented as encapsulations of efficient low-level manipulations.

Lisp is the world’s greatest programming language—or so its proponents think. The structure of Lisp makes it easy to extend the language or even to implement entirely new dialects without starting from scratch. Overall, the evolution of Lisp has been guided more by institutional rivalry, one-upsmanship, and the glee born of technical cleverness that is characteristic of the “hacker culture ” than by sober assessments of technical requirements. Nevertheless this process has eventually produced both an industrialstrength programming language, messy but powerful, and a technically pure dialect, small but powerful, that is suitable for use by programming-language theoreticians. We pick up where McCarthy’s paper in the first HOPL conference left off. We trace the development chronologically from the era of the PDP-6, through the heyday of Interlisp and MacLisp, past the ascension and decline of special purpose Lisp machines, to the present era of standardization activities. We then examine the technical evolution of a few representative language features, including both some notable successes and some notable failures, that illuminate design issues that distinguish Lisp from other