Recursive Data Types in Setl: Automatic Determination, Data Language Description, and Efficient Implementation (Compilers)

Candidate: Weiss,Gerald


Very high level languages are often weakly typed in the sense that different occurrences of a name can be associated with distinct types. The types of many entities are nevertheless determinable from the structure of the program, allowing translators for these languages often to incorporate some sort of typefinding algorithm. Due to problems of algorithmic termination, however, these algorithms have been unable to type structures of a recursive nature such as trees. In this thesis we present a method which detects and uncovers the structure of recursive objects, and discuss possible applications of the method to optimization of code. We examine the run-time type model of SETL and the corresponding data representation sublanguage (DRSL), and present a general critique of the design as well as implementation of the current data representation sublanguage. The objects expressible by the latter are shown to be proper subsets of the universe of types assumable by SETL entities at run-time; we present suggestions for extending the representation sublanguage to allow for complete type specification.