APL to Ada translator

Abstract

PurposeThe purpose of this programming effort is to build a r&able, automatic, special-purpose translator from APL code into Ada code.'The goal is to enable an algorithm designer to prototype an algorithm rapidly, debug it, and test it in APL (specifically, APL2); then to translate it quickly, compile it, and execute it in the Ada environment. This gives the dual advantages of the quick and easy development and debugging capabilities of APL2 and the large-project maintainability of the Ada environment. An additional benefit is to minimize the amount of debugging in Ada, which in turn minimizes the number of resource-intensive Ada compilations.Since both APL and Ada are very general, powerful languages, developing a general or complete translator from one to the other would be a tall order indeed. For practical reasons this effort has been restricted to translating mathematically oriented algorithms which might normally be developed using only static, rectangular arrays with floating point and integer types. Many algorithms used in military software applications today are in this category.Of course, both APL and Ada easily accommodate dynamic (non-static) arrays, and it is desirable in many situations to program in a manner which uses this capability. The main penalty is an increase in computer resource requirements, which the project at hand (DSP System 1 Mission A) cannot tolerate. Thercforc, the judgcment call was to emphasize static arrays.An additional consideration was that since the resulting Ada code is intended for real-time use, the translator must not introduce artificial incfftcicncies of execution in the resulting Ada code. The APL user must be able to create APL code which will be translated into Ada code which is as efftcient as an Ada programmer would be expected to generate manually.Finally, the user should also have a high degree of control over the readability of the resulting Ada code, At a minimum, APL comments should be translated appropriately into Ada comments. The Ada control statements used should be among the most natural for the application. Also, standard code indentation should be applied.

The IBM family of APL systems

“…45 The APL acceptable to this translator had to be highly stylized, but it nevertheless turned out to be useful in an important prototyping application. The translator was written in APL2, and had the limited goal of allowing an algorithm designer to prototype rapidly in APL and, after debugging there, translate the program to Ada for compilation and running in that environment.…”