Paolo Amoroso's Journal

I started working on the class Universe of GravityLoops, my gravity simulator in Interlisp and LOOPS. I defined the class itself and the main methods, Universe.Register and Universe.Simulate.

The class represents a collection of bodies and manages the parameters and state of the simulation. Universe.Register adds a body to a universe, Universe.Simulate runs the simulation.

In the C++ code of the article my design draws inspiration from, an instance variable of the class UNIVERSE holds a pool of bodies in an array, with the most recently added body indexed by another instance variable. In GravityLoops the corresponding instance variable bodyPool is a list which, as the article notes, is more versatile and doesn't need the index.

Universe.Simulate, just a stub for now, is the core method. It will update the state of the simulation, display the bodies in a graphical window along with status information, and check whether the user interrupts the simulation. The C++ program runs the simulation until the user presses a specific key and GravityLoops will have a similar feature. I'll also have the program accept a number of time ticks to step the simulation through.

For Universe.Simulate I'll mostly follow the C++ code. But I plan to revisit the decision after I have something running to experiment with. I may want to split the simulation functionality into more than one method to separate the simulation itself from output, or redesign control around LOOPS' active values.

#GravityLoops #Interlisp #Lisp

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