# Conventions¶

## Style¶

• Tabs for indentation, compact formatting.

• Avoid spurious spaces, like before parentheses, except in complex expressions.

• Comment so that code functionality is visible, don’t comment when the code says it better than the comment.

• Use struct instead of class (everything public by default).

• Start header files with #pragma once.

• Headers are .hpp, implementations are .cpp.

• Include all headers using #include<woo/pkg/dem/Particle.hpp>, do not use #include"Particle.hpp".

• Do not say using namespace, not in headers and not in implementation files.

• Put only short methods inline in headers, when important for performance.

• Mark const arguments with const.

• Pass by const reference as much as possible.

• Mark methods as const if they can be.

• When overriding virtual function, mark it with WOO_CXX11_OVERRIDE (expands to the override keyword for compilers which support it).

• Put assertions in the code, they expand to nothing in non-debug builds.

• Be defensive; for user-called functions, check that arguments make sense, raise exception if they don’t.

• Document everything.

• Use logging macros as necessary.

## Types¶

Many types are declared in lib/base/Types.hpp. Those include types imported from std or boost namespaces (like shared_ptr, make_shared, vector, string, to_string, cout, cerr, min, max, isnan and many others). A shorthand for boost::python is defined, namely py (so one can use py::extract and such).

Be conservative with memory usage, so unless there is a reason for that, use int rather than long. For floating-point numbers, Woo uses the type Real everywhere, which is typedef for double (by default, that is).

### Math types¶

Eigen is our math library. Frequently used types are typedef’d with the r suffix for Real and i for int:

• vectors with Real scalars: Vector2r, Vector3r, Vector6r, VectorXr (dynamic-sized)

• vectors with int scalars: Vector2i, Vector3i, Vector6i

• matrices with Real scalars:: Matrix3r (3×3), Matrix6r (6×6), MatrixXr (dynamic-sized)

• aligned boxes AlignedBox2r, AlignedBox3r, AlignedBox2i, AlignedBox3i

• quaternions Quaternionr, angle-axis rotation AngleAxisr

Two importants constants are NaN and Inf. For $$\pi$$, use plain old M_PI.

## Feature macros¶

Woo has a number of features which can be enabled/disabled at compile-time. Those are passed as features=... argument to scons, can be retrived from python as woo.config.features and are available in c++ as macros WOO_, e.g. WOO_OPENGL. Note that builds without some feature must still compile and work, so any feature-specific code must be guarded by macros, e.g. for OpenGL:

#ifdef WOO_OPENGL
/* ... */
#endif


Non-exhaustive list of features is:

• WOO_DEBUG: defined in debug builds.

• WOO_OPENGL: support for OpenGL 3d graphics; disabled on headless (cluster) builds.

• WOO_OPENCL: support for OpenCL; experimental only.

• WOO_QT4: support for Qt4 user interface.

• WOO_VTK: have headers and libs of Visualization ToolKit.

• WOO_GTS: have headers and libs of GNU Triangulated Surface. Those are very useful for working with facets, don’t disable.

## Namespaces¶

Woo is at the moment not very consistent putting everything into the woo namespace. As Woo is dypically used as python module, the organization into Python modules (which is independent) is more important.

## Logging¶

Logging macros are for helping development or diagnostics, defined in lib/base/Logging.hpp. The logging backed is currently log4cxx, but this may change in the future. Logging is controlled per-class. Any class wishing to use logging should declare logger within the class body in the header file using WOO_DECL_LOGGER and do additional setup (allocation) in the implementation file using WOO_IMPL_LOGGER(Rabbit) at the top-level scope.

The lower macros are ignored in non-debug builds:

• LOG_TRACE, LOG_DEBUG, LOG_INFO: increasing severity levels. Tracing is for low-level debugging with possibly copious output, debug is more severe. Info level should provide manageable amount of information even when globally enabled.

• LOG_WARN is used for warning about non-fatal conditions.

• LOG_ERROR informs about erroneous condition; if the condition likely caused by the user, it may be better to throw an exception instead, since that allows for better diagnostics.

• LOG_FATAL informs about a fatal condition, and is often followed by crash or an exception being thrown.

## Renaming classes¶

Sometimes, classes are to be renamed for consistency. This may pose some problems with backwards-compatibility. For this reason, there is woo._monkey.aliases._deprecated: old name may still be used, but there will be a waning issued, along with the location of the offending code.

## Unit tests¶

Make sure your modifications don’t break existing code. There is a (rather limited) unit test suite which should be always run after modifications; it is launched with woo --test`.

When adding new functionality, adding a unit test for it is the best way to keep the interface stable (other people will see if they break it immediately).

Tip

Report issues or inclarities to github.