A “WAIT UNTIL” algorithm for general purpose simulation languages

Modern simulation languages such as SIMSCRIPT II and SIMULA 67 are very powerful general purpose languages which contain facilities to handle lists and to schedule events in simulated system time (imperative sequencing statements). These languages do not include some of the useful but more specialized features of previous languages (GPSS, CSL, SOL) especially interrogative sequencing statements such as “SEIZE (facility)” or “WAIT UNTIL (Boolean expression)”; however, the definition capability of the new languages is powerful enough to permit their extension to include the interrogative features. The addition of some features of GPSS to SIMULA 67 was presented at a previous SIMULATION CONFERENCE. The present paper extends that work by describing an efficient algorithm which adds the “WAIT UNTIL” procedure to SIMULA.