A Visual Programming Environment for Functional Programs

The purported advantages of Visual Programming, as applied to general purpose programming languages, have remained largely unfulfilled. The essence of this thesis is that functional programming languages have at least one natural visual representation, and that a useful programming environment can be based upon this representation. This thesis describes the implementation of a Visual Functional Programming Environment (VFPE). The programming environment has several significant features. • The environment includes a program editor that is inherently visual and interactive: syntactic program components have a visual representation and are assembled via a graphical interface. • The program editor incorporates a static analysis system that tracks types for the whole program, making it impossible to construct syntactically incorrect or type-incorrect programs. Type information is continually and explicitly available to the programmer. • The environment implements an implicitly typed higher-order purely functional language without conforming exactly to any particular language with respect to syntactic structures or reduction semantics. • Programs can be output as source code for an existing functional language. • The visual representation allows for continued experimentation with new syntactic features. Some currently included features are algebraic data types, pattern matching, and guarded expressions. • The environment includes a visual interpreter which allows any expression to be reduced in source form, with a choice of reduction behaviors. Please note that this thesis was written to be read in conjunction with a set of animated examples. The examples should be present on some form of digital media accompanying this thesis: at the points indicated in the thesis text, the reader should view the associated example.