Aims

Creating and maintaining a mathematical and statistical library that is accurate requires a greater degree of communication than might be the case for other components. It is important that developers follow guidelines laid down by the community to ensure that the code they create can be successfully maintained by others.

Guidelines

Developers are asked to comply with the following development guidelines. Code that does not comply with the guidelines including the word must will not be committed. Our aim will be to fix all of the exceptions to the should guidelines prior to a release.

Contributing

Coding Style

Hipparchus follows a specific coding style, similar to the ones used in Apache Commons projects or the Orekit project. The reference settings correspond to the src/conf/checkstyle.xml file found in the Hipparchus source tree. There is also a src/conf/hipparchus-eclipse.xml file that configures the eclipse formater in a mostly compatible way (there are some parts that cannot be configured automatically in Eclipse to match checkstyle settings, mainly in the indentation parts). One thing that Checkstyle will complain about is tabs included in the source code. Please make sure to set your IDE or editor to use spaces instead of tabs.

Committers should configure the user.name, user.email and core.autocrlf git repository or global settings with git config. The first two settings define the identity and mail of the committer. The third setting deals with line endings to achieve consistency in line endings. Windows users should configure this setting to true (thus forcing git to convert CR/LF line endings in the workspace while maintaining LF only line endings in the repository) while OS X and Linux users should configure it to input (thus forcing git to only strip accidental CR/LF when committing into the repository, but never when cheking out files from the repository). See Customizing Git - Git Configuration in the git book for explanation about how to configure these settings and more.

Documentation

• Committed code must include full javadoc.
• All component contracts must be fully specified in the javadoc class, interface or method comments, including specification of acceptable ranges of values, exceptions or special return values.
• External references or full statements of definitions for all mathematical terms used in component documentation must be provided.
• Hipparchus javadoc generation supports embedded LaTeX formulas via the MathJax javascript display engine. To embed mathematical expressions formatted in LaTeX in javadoc, simply surround the expression to be formatted with either \( and \) for inline formulas, or \[ and \] to have the formula appear on a separate line. For example, \(a^2 + b^2 = c^2\) will render as an in-line formula \(a^2 + b^2 = c^2\). Using \[ and \] on the ends will render the same formula on a separate line. See the MathJax and LaTex documentation for details on how to represent formulas and escape special characters.
• Hipparchus modules documentation for the web site is generated using markdown syntax. It also supports embedded LaTeX formulas via the MathJax javascript display engine. To embed mathematical expressions formatted in LaTeX in markdown, simply surround the expression to be formatted with either \\( and \\) for inline formulas, or \\[ and \\] to have the formula appear on a separate line. For example, \\(a^2 + b^2 = c^2\\) will render an in-line formula \(a^2 + b^2 = c^2\). Using \\[ and \\] on the ends will render the same formula on a separate line. See the MathJax, markdown and LaTex documentation for details on how to represent formulas and escape special characters. Note that as the markdown processor needs backslash characters to be escaped, you have to double them (so for example in order to mark the end of a matrix row with a TeX double backslash, you need to type four backslashes in the markdown file)
• Implementations should use standard algorithms and references or full descriptions of all algorithms should be provided.
• Additions and enhancements should include updates to the User Guide.

Exceptions

• Exceptions generated by Hipparchus are all unchecked.
• All public methods advertise all exceptions that they can generate. Exceptions must be documented in both javadoc and method signatures and the documentation in the javadoc must include full description of the conditions under which exceptions are thrown.
• Methods should fully specify parameter preconditions required for successful activation. When preconditions are violated, a MathIllegalArgumentException should be thrown. Exception messages must contain sufficient information on parameter values to determine the exact precondition failure.

Unit Tests

• Committed code must include unit tests.
• Unit tests should provide full path coverage.
• Unit tests should verify all boundary conditions specified in interface contracts, including verification that exceptions are thrown or special values (e.g. Double.NaN, Double.Infinity) are returned as expected.

Licensing and copyright

• All new source file submissions must include the Hipparchus project header in a comment that begins the file,
• Recurring contributors must file an Hipparchus Individual Contributor License Agreement (ICLA) (Open Document Format, Portable Document Format) or Corporate Contributor License Agreement (CCLA) (Open Document Format, Portable Document Format)
• Importing pre-existing code into Hipparchus requires filing a Software Grant (Portable Document Format)
• Patches must be accompanied by a clear reference to a source, - if code has been ported from another language, clearly state the source of the original implementation. If the expression of a given algorithm is derivative, please note the original source (textbook, paper, etc.).
• References to source materials covered by restrictive proprietary licenses should be avoided. In particular, contributions should not implement or include references to algorithms in Numerical Recipes (NR). Any questions about copyright or patent issues should be raised on the developers forum before contributing or committing code.

Recommended Readings

Here is a list of relevant materials. Much of the discussion surrounding the development of this component will refer to the various sources listed below, and frequently the Javadoc for a particular class or interface will link to a definition contained in these documents.