| On Guards (1987) | |||||||||||||||
Abstract | |||||||||||||||
| This is a note about the distinction in occam between inputs and outputs, and between those inputs that appear as guards and those that appear as processes in their own right. It explains the restriction that outputs may not appear as guards in occam programs, and records programming techniques for coping with this restriction. An occam programmer will from time to time find himself complaining that something would be so much easier if occam allowed output guards. There is an apparently arbitrary asymmetry in occam's allowing inputs to guard alternatives, but forbidding outputs. First I explain why output guards are forbidden in occam. Essentially, it is very expensive to implement general input and output guards. There are then presentations of systematic ways of eliminating output guards from a csp program as a way of translating it into occam without incurring the prohibitive costs of general guards. There is no claim that the techniques are new, but experience at previous meeting... | |||||||||||||||
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