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LHAPDF  6.2.1
Coding style

LHAPDF C++ CODING STYLE

A short guide for developers and patch suppliers on the C++ coding style used in LHAPDF >= 6.

  • The basic style is the "one true brace style". The exception is for constructors with initialisation lists, in which case the function body should be opened by a brace on its own on a new line, rather than the brace trailing the init list entries.
  • Indent! The standard indent size in the current code is two spaces. Do not indent with tab characters.
  • Infix operators like = (assignment), logical comparators (==, !=, >, <, >=, etc.), + and -, and all arithmetic modifying operators (+=, -=, *=, /=) should be separated from their arguments on either side by a single space. Spaces are cheap, the time taken to decipher hyper-compressed code is not! The * and / operators should be padded like this if it aids readability, but not otherwise: it is useful to visually distinguish addition of terms from the multiplications/divisions which compose them.
  • The parenthetical condition statement of an "if", "for", "while", etc. block should be separated from the "if" etc. keyword and from the opening brace of the block by one space. The contents of the parenthesis should not be space-padded, however, unless it is necessary for clarity (the same applies to function arguments). For example, "if (foo > bar) { ...". Again, spaces are cheap: use them.
  • Braces are encouraged around all but the most trivial control blocks: if you cannot put the one-line block content on the same line as the block condition statement, or if there is any visual ambiguity about which lines are in the block body, add braces.
  • if-statement and exception continuations should normally be on the same line as the delimiting braces in 1TBS fashion, e.g. "} else {", "} else if (foo != bar) {", etc.
  • All code should be in the LHAPDF namespace. In .cc files, unnamed namespaces should be used to hide implementation detail functions from public/ABI view.
  • Class names are in CamelCase format, and method and function names in lowerCamelCase. In the class names "PDF" is always kept fully capitalised, while in method and function names it may appear as "pdf" or "Pdf" depending on context: try to be consistent with the "local environment". Private or protected members, or more generally any API element not designed for public use should start with a leading underscore, cf. _implementationDetail.
  • Separate blocks within functions by a blank line, separate functions by two blank lines, and separate class definitions by 3 blank lines. Two blank lines of separation should be left between the main LHAPDF namespace opening and closing braces and the first and last code lines in the namespace. These are just guidelines: if more lines of separation than these nominals are needed for visual clearance of distinct code elements, add more: blank lines are also pretty cheap, but don't go crazy or you'll hardly be able to fit any lines of active code on your screen!
  • Use the specialised LHAPDF exceptions from LHAPDF/Exceptions.h. Exceptions should be used rather than asserts unless there is absolutely no way that the tested condition could happen other than a bug in the system: the user should be able to catch their own errors.
  • We're relying on the Boost and yaml-cpp libraries, but currently no others. Get a feel for what is available in Boost, and in the LHAPDF/Utils.h header: do not reinvent the wheel.
  • "Flavour" is spelt the American way, "flavor" in all places in the code, for definiteness.
  • Use comments! Describe what sections of not-immediately-clear code do in as clear and concise a way as possible, preferably on one line. In header files use Doxygen /// comments and operators with an @ delimiter (particularly "@todo") to describe the meanings of classes, methods, their arguments, etc. While writing code it's often best to leave some details until later – mark these with a "@todo" operator and a description of the missing feature: these will be collected into a helpful list by Doxygen.
  • If in doubt, ask!

THANKS FOR READING :-)