MOST-flexiPL: modular, statically typed, flexibly extensible programming language

Abstract

Even though extensible programming languages have been around for decades, they have not received much attention so far. To obtain a more attractive solution, where extending the language is almost as easy as writing normal programs, extensibility should not be provided as a separate add-on, but rather as the very heart of the language. Furthermore, syntactic flexibility should not only allow to extend, but also to completely change the syntax when desired. MOSTflexiPL follows this approach by allowing users to define new operators, control structures, type constructors, and even declaration forms almost as easily as functions without sacrificing static type safety. This is achieved by encoding all constructs as generalized operators possessing any number of names and operands in an arbitrary order, where users have full control over associativity, precedence, and even scoping rules. Even though the language is still under development, there is a working compiler that translates MOSTflexiPL programs to equivalent C++ code.