Hi Peter,
About continuous time; it is in fact, not really continuous is it, since floats are used to approximate time. So the longer your program runs, the less accurate an absolute time value will become no?
Well, yes and no. Yampa, at least, does not use absolute time internally, only time deltas, so the problem you describe only occurs if the programmer *explicitly* choose to accumulate absolute time, or *explicitly* make use of very large relative time intervals (e.g. combinators like "after" that emits an event after a given, relative, time interval). So, as always with floating point, or with any finite representation of numbers, the programmer has to understand the limitations and implications of the chosen representation. But this is not any inherent flaw of FRP or its Yampa incarnation as such. One could also imagine using some infinite-precision number representation with FRP instead of floating point. The fact that Yampa uses floating point is merely a pragmatic implementation choice. I believe I also saw someone asking about Modelica in this context. Modelica is a hybrid modelling and simulation language. Efficient simulation and accurate results are of key importance, and for that reason Modelica implementations use sophisticated numerical and symbolic methods. Unfortunately, this also limits the expressiveness of the language. In particular, Modelica cannot handle systems with highly dynamic structure like video games. Thus I don't think we'll see video games written purely in languages like Modelica any time soon, even if there is active research on making such languages cope better with structurally dynamic systems. (One could probably imagine using Modelica for handling game physics, though, i.e. as a component of a games programming suite.) Best, /Henrik -- Henrik Nilsson School of Computer Science and Information Technology The University of Nottingham nhn@cs.nott.ac.uk This message has been checked for viruses but the contents of an attachment may still contain software viruses, which could damage your computer system: you are advised to perform your own checks. Email communications with the University of Nottingham may be monitored as permitted by UK legislation.