Application of Advanced Ada Language Features to Data Structures in a Graphics Programming Environment

摘要

The application of language features to the large scale access of a non-Ada graphic library was demonstrated. Implementation of abstract interfaces within a graphical environment was accomplished (most notably between a FORTRAN-based Graphical Kernel System (GKS) and ANSI standard (draft) GSK/Ada). Finally, Ada language features were examined as vehicles for graphics modeling applications. Two graphics programming environments were developed. The first employed the Ada pragma INTERFACE feature to achieve broad access to a FORTRAN library of GKS commands. An interface then mapped the pragma-based procedures to a user interface based on the standardized (draft) ANSI-GKS/Ada language binding. The second environment, implemented through calls to the first, focused strictly on the creation and display of graphics data in a hierarchical structure. The approach was based on concepts of the Programmer's Hierarchical Interactive Graphics Standard (PHIGS). Though numerous applications were made of advanced Ada features, several were identified as having particular significant in graphics applications. They include: generic definition of multiple coordinate systems, use of unconstrained array types for data manipulation, judicious application of Ada's use statement to manage access of graphics libraries, and employment of discriminated types to store graphics data for subsequent display.