Writing new code

The easiest way to start writing new functions and classes is to create a new module using the make-module.py script. This creates a new module in the modules directory. Alternatively, you can simply use the scratch module.

If, instead, you choose to add code to an existing module, you need to consult with the maintainer of that module. Their GitHub username can be found on the module main page.

Either way, we highly recommend doing this in a git clone, as described earlier, then using git to keep track of changes to your code.

When designing the interface for your new code, you should

• think about what exactly is the functionality you want to contribute. Is it a single function, a single Restraint, a set of related classes and functions?
• search IMP for similar functionality and, if there is any, adapt the existing interface for your purposes. (It might make more sense to modify the existing code in cooperation with its author.) For example, the existing IMP::atom::read_pdb() and IMP::atom::write_pdb() functions provide templates that should be used for the design of any functions that create particles from a file or write particles to a file. Since IMP::atom::Bond, IMP::algebra::Segment3D and IMP::display::Geometry all use methods like IMP::algebra::Segment3D::get_point() to access the endpoints of a segment, any new object which defines similar point-based geometry should do likewise.
• think about how other people are likely to use the code. For example, not all molecular hierarchies have atoms as their leaves, so make sure your code searches for arbitrary IMP::core::XYZ particles rather than atoms if you only care about the geometry.
• look for easy ways of splitting the functionality into pieces. It generally makes sense, for example, to split selection of the particles from the action taken on them, either by accepting a IMP::Refiner, a IMP::SingletonContainer or just an arbitrary IMP::ParticleIndexes object. Similarly, rather than writing a Restraint, it may make more sense to write an IMP::PairScore or IMP::UnaryFunction; an IMP::SingletonModifier may be more appropriate than an IMP::Constraint.

You are encouraged to post to the imp-dev list to find help answering these questions as it can be hard to grasp all the various pieces of functionality already in the repository.

See also the IMP::example module, which contains many examples of writing new IMP functionality in C++ or Python. You may also want to read the design example for some suggestions on how to go about implementing your functionality in IMP.