MERCURIUS update coming soon

[hannorein]

I'm working on an update to the Hybrid Symplectic Integrator in REBOUND. Currently there are two of these integrators MERCURIUS and HERMES. It now seems more and more as if there is no case where HERMES is superior to MERCURIUS. I will therefore remove HERMES to avoid confusion and help maintainability. There will also be a few minor syntax changes for MERCURIUS. Also, MERCURIUS will work more reliably in simulations where physical collisions might occur. The current development is done on the mercuriusrelease branch.

[hannorein]

I am also trying to define a style and naming convention for functions and variables. I don't plant to implement this across the entire codebase right now, but it can serve as a reverence whenever a particular module gets updated. Some of this takes inspiration from PEP8. The C and python syntax should be as close as possible. I will put the final conventions in the documentation, but post it here first in case anyone has any suggestions.

Functions (c):

• All non-static functions have the prefix reb_
• All lower case
• Multiple words are connected with underscores
• "Sentences" should follow "noun_verb" rule, where "noun" is the object that gets operated on. For example: reb_simulation_create() and reb_simulation_free()
• All functions belonging to a specific module have a common prefix. For example: reb_integrator_whfast_kepler_step(). This might get long, but note that this is only really required for functions intended for general use. Internal functions can be static and do not need to include the prefix.

Variables (c):

• The function naming convention rules apply.
• The only public variables are in structs. Therefore they do not have the reb_ prefix.
• As an exception to the lower case rule: the number of particle N is capitalized.
• Variables beginning with an underscore are not intended for general use.

Objects (python):

• First letter is capitalized, all other letters are lower case
• Same name as in corresponding c struct except reb_ prefix. For example struct reb_particle is Particle.
• Instance methods in python drop the reb_ prefix and the noun from the corresponding c function. For example reb_simulation_move_to_com() becomes Simulation.move_to_com().

Specific function names (c):

• "create" describe a method which both allocates memory for the struct and then initializes the object. For example: reb_simulation_create()
• "reset" describes a method which resets the struct to (more or less) its initial values such that it can be used as if a new object was created. For example: reb_integrator_ias15_reset().

Header files (c):

• All structs and function definitions that a user might need to access are in rebound.h.
• Structs and function definitions that are specific to one module and are only used internally within the rebound library are in the module header files. For example: integrator_whfast.h.

Indentation:

• Four spaces are used both in c and python for indentation.

[hannorein]

Closed via a1e1b73a