Interactive visual functional programming
Keith J. Hanna · 2002
An interactive graphical environment for supporting the development and use of Haskell applications programs is described. The environment, named Vital, is particularly intended for supporting the open-ended, incremental development style often preferred by non-specialist users in which successive steps of program development are motivated and informed by results so far obtained.Significant features of Vital include: the graphical display of data structures in a format defined by a datatype-indexed stylesheet, the way that evaluation of (possibly infinite) values is demand-driven by the action of the user scrolling around an unbounded workspace, and support for copy-and-paste graphical editing of data structures. This latter allows, for example, the user to modify a complex data structure by point-and-click operations, or to create (by functional evaluation) a regular data structure and then edit values or expressions into it. The effect of each editing operation is immediately reflected in the Haskell program source code.