Bugzilla – Bug 2
Time class a full-blown arithmetic object
Last modified: 2008-07-01 13:32:11 EDT
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Currently, it is not possible to do arithmetic with the Time class itself. Instead, we ask our users to do their own calculations and then to convert their final time into a Time object prior to invoking the simulator's Scheduler methods. It might make sense to add a bunch of arithmetic operators to this c++ class to make it possible for users to use it directly to do their calculations. We could use this to catch common overflow or underflow errors. What is not super clear is how to handle substractions of Time objects: what would be the type of the returned object ? This bug comes from the ML discussion on ns-developers archived here: http://mailman.isi.edu/pipermail/ns-developers/2006-October/002433.html
I would like to add one extra comments: It might be really needed to go down that route because the current way of allowing the user to convert to various time units is sort of broken. Part of the deal when I designed the current Time getters was that the user would see no change in simulation behavior if we increased the internal accuracy of the event scheduler. However; this does not work in practice: if the code was designed to say: I want to schedule an event in 2 microseconds and if he used Schedule (Now + 2) to do this, his code might not be notified in 2 microseconds but in 1+epsilon microseconds due to the way time conversions are done. So, I think that the current way of working is bad in certain cases (which ought not to exist I should point out) So, I guess that the priority of this item has just increased in my work queue.
The Time class now behaves like a full C++ POD. i.e., arithmetic operators are implemented, including +-*/.