Compiling a simulation language in APL

This paper describes the procedure used to build several compilers, written in APL and APL2, to translate two continuous simulation languages imo APL and C+ +. The advantages and disadvantages of using APL to write a compiler are discussed. A compromise had to be found between performance (the model execution speed) and flexibility (the ease to modify parameters and test "what if " situations). The resuhing compiler (an APL2 packaged workspace) has been used successfully to generate ducational pplications and in medical research. In t roducUon System simulation [1] is one of the oldest branches of computer science. It was well advanced in the sixties, and came to maturity in the seventies. Its objective is to build a "model " of a real system, i.e. a system that behaves in a similar way as the real system, but is easier to study and experiment with. If the mode] is a set of mathematical equations, it is called a "mathematical model". If it is a computer program, we have a "computer model". There are three kinds of computer simulation: • Analog simulation: time is continuous. Models are built by means of electronic ircuits in an "analog computer", invented by Vannevar Bush in the nineteen thirties. Analog computers are now outdated. Permission zo make digital or hard copies of all or pad of this work for personal or classroom usa is granted without lee provided that copies are not made or distributed for prolix or commercial advant-age and that copies bear this notice end the full can iLion on the first page. 'To copy otherwise, to republish, to post on servers or to redistribute to lists, requires prior specific permission and/or a fee