APL2

APL2, short for A Programming Language 2, is a dialect of the APL family designed to blend APL’s powerful array-oriented notation with traditional programming constructs. It was developed by Kenneth E. Iverson and Roger Hui at IBM and released in the late 1980s as a successor to the original APL. APL2 retained APL’s concise array operations while introducing features aimed at more conventional software development, such as modular programming, user-defined functions, and improved program structure. It also offered an ASCII-based syntax option in addition to the traditional APL symbol set, making the language more accessible in standard editors and on diverse platforms.

Key characteristics of APL2 include a strong emphasis on array processing, combining monadic and dyadic operations with higher-order functions. The language supports modules and reusable code, enabling developers to build larger programs and libraries. It provides structured programming facilities, including control constructs for conditional execution and looping, while preserving the core APL semantics for arrays and multidimensional data.

Historically, APL2 was used on IBM systems and later ported to various platforms, including Unix-like environments and personal computing setups. It contributed to the broader spread of ASCII-based APL and influenced later array-oriented languages and tools. Today, APL2 is largely considered of historical interest, with modern descendants such as Dyalog APL, GNU APL, and related dialects continuing the tradition of array programming. IBM’s APL offerings have evolved, but APL2 remains a notable milestone in the development of practical, production-oriented APL implementations.