Section: New Results

Dynamic Languages: Compilers

Towards a flexible Pharo Compiler The Pharo Smalltalk-inspired language and environment started its development with a codebase that can be traced back to the original Smalltalk-80 release from 1983. Over the last years, Pharo has been used as the basis of many research projects. Often these experiments needed changes related to the compiler infrastructure. However, they did not use the existing compiler and instead implemented their own experimental solutions. This shows that despite being an impressive achievement considering its age of over 35 years, the compiler infrastructure needs to be improved. We identify three problems: (i) The architecture is not reusable, (ii) compiler can not be parametrized and (iii) the mapping between source code and bytecode is overly complex. Solving these problems will not only help researchers to develop new language features, but also the enhanced power of the infrastructure allows many tools and frameworks to be built that are important even for day-to-day development, such as debuggers and code transformation tools. [20]

Gradual Typing for Smalltalk Being able to combine static and dynamic typing within the same language has clear benefits in order to support the evolution of prototypes or scripts into mature robust programs. While being an emblematic dynamic object-oriented language, Smalltalk is lagging behind in this regard. We report on the design, implementation and application of Gradualtalk, a gradually-typed Smalltalk meant to enable incremental typing of existing programs. The main design goal of the type system is to support the features of the Smalltalk language, like metaclasses and blocks, live programming, and to accomodate the programming idioms used in practice. We studied a number of existing projects in order to determine the features to include in the type system. As a result, Gradualtalk is a practical approach to gradual types in Smalltalk, with a novel blend of type system features that accomodate most programming idioms. [13]