R3RS

R3RS stands for Revised-3 Report on the Algorithmic Language Scheme. It is an early formal specification of the Scheme programming language, one of the dialects of Lisp. The document provides a defined core language and a standard library subset intended to support portable implementations and program compatibility across different schemes.

The report describes the core syntax and the evaluation rules for Scheme expressions, the structure of environments and bindings, and the behavior of standard procedures. It emphasizes features associated with Scheme, such as first-class procedures and lexical scoping, and it addresses the handling of tail recursion and basic control constructs within the language core. While the exact details can vary among implementations, R3RS establishes a shared baseline for how Scheme programs should behave.

R3RS served as a bridge within the Scheme standards lineage, contributing to the foundations later refined in subsequent reports. It helped standardize terminology and conventions that were carried forward by later iterations, and it supported the broader goal of language portability across different Scheme systems. Although newer standards have expanded the language and library beyond its scope, R3RS remains a relevant historical reference for understanding the evolution of Scheme and its community’s approach to formal specification.

Relationship to related standards: R5RS, widely recognized for its influence on later Scheme developments, followed earlier iterations such as R3RS and R4RS. The R3RS publication is often cited in historical discussions of Scheme’s standardization and its progression toward larger, more feature-rich specifications.