This is a list of conventions, which should be followed in developing MarlinTPC -- at least for commits to the trunk.

Please take these conventions with a grain of salt, as they have been devised way back in the beginnings of MarlinTPC. It is planned to integrate them into the repository, so they can be maintained and updated in a collaborative spirit.

= General Conventions =
In all following steps no compiler warnings shall remain with the compiler set to all warnings on and pedantic mode!

Please use the ''new'' way of log informations, which is very similar to using std::cout:

{{{ streamlog_out($LEVEL) << "sending a message out" << endl;}}}

where the $LEVEL is something from DEBUG0-4,MESSAGE0-4,WARNING0-4,ERROR0-4 (e.g. DEBUG2, MESSAGE, ERROR3).

/!\ The command {{{m_out($LEVEL)}}}, still seen in some older branches, is deprecated by ilcsoft and will result in compile errors!

= Code style conventions =
== Keep it simple! ==
Use ANSI C++, STL, containers, standard MarlinTPC algorithms.

== Revision and Parameter Logging ==
Implement revision and parameter logging according to the [[HowToDevelopMarlinTPC|MarlinTPC Developer Workbook]]. Don't forget to execute svn propset!

== Nesting ==
Try to avoid deep (about three is tolerable) nesting of statements like for, if, while, do. It will decrease both, performance and readability.

== Casts ==
Often casts can even be avoided by a sensible declaration of variables. If not, use explicit C++ casts:

{{{    dynamic_cast<type>(variable)}}} e.g. for converting collections to the real LCIO objects.

 . static_cast<type>(variable) instead of C-type casts (e.g. static_cast<float>(variable) instead of (float) variable)

 . reinterpret_cast<type> is needed when reading from a binary stream, otherwise I never encountered it.

== STL Containers ==
Use iterators for STL containers.

'''Naming''': itContent (e.g. {{{itPulses}}})

Iterators are usually used within loops. In many cases it is convenient to generate a local object or reference from/to the content of the collection iterator. That saves dynamic_cast statements and enhances readability.

== Exception Handling ==
Perform exception handling! Think what could go wrong when issuing commands in the code and provide a controlled routine for handling these cases. If you can avoid error states by checking with if conditions do that.

If you need to cope with error states and can't avoid them before they happen: try ... catch blocks are preferred for this, Marlin provides some exceptions already:

assert statements should only be use for debugging. Don't forget to {{{#define NDEBUG}}} before committing your code if you are using assert statements.

Remember to notify the user by logging output (see Logging).

== Logging ==
Use {{{streamlog_out(Level)}}} instead of {{{cout}}} , because severity levels can be assigned and the issuing processor is printed.

== Obsolete Code ==
Fragments Check for and remove obsolete variables, functions, types, constants, #include statements and other unused code fragments.

== Constants ==
Avoid unmotivated numbers in the code, but make them (local) constants with a meaningful name (e.g. instead of {{{0.78125}}} say {{{TDC_TIME_BIN_WIDTH}}}).

'''Naming''': all letters upper case, "words" connected with underscores (example: see above)

Don't use #define constants. Replace them by static const variables.

The only exception is the mandatory {{{#ifndef PROCESSOR_HEADER_FILE_NAME_H #define PROCESSOR_HEADER_FILE_NAME_H = 1 #endif}}} construction in the header file to steer the compiler.

Declare public member variables always as {{{const}}}.

== Variables ==
'''Naming''': first word starts with lower case letter, following words start upper case (e.g. myFancyVariableName)

'''Naming of member variables in protected and private''': The current Marlin rule is to start with underscore, after that like non member Variables (e.g. _myMemberVariable).

'''''Warning:''''' ''According to C++ (GNU) coding recommendations, variables with leading underscore(s) may be reserved by the implementation. A solution to this unfortunate situation is currently under discussion and will be announced to the collaboration. In order to facilitate possible automatic changes on the code base, please continue to use the current rule for the time being.''

Declare variables as local as possible (Where in the code is it used?).

Declare them clearly at the beginning of the corresponding code block.

Check whether using a constant would be sufficient (Perhaps the variable doesn't change anyway after its initialization?).

Try to name variables as meaningful as possible, which includes to avoid abbreviations. If they are not avoidable (say for lengthy formulas) provide extensive commentary text and think of using Doxygen where LaTeX statements are possible.

Especially for boolean variables names containing "is" or "has" can be very helpful for reading boolean expressions.

This holds for naming in general!

== Type names ==
(declared by {{{class, typedef, struct}}})

'''Naming''': each word starts upper case (e.g. !FancyClass()). If the class describes a MarlinTPC Processor include Processor at the end of the class name (e.g. !VeryComplicatedTaskSolverProcessor()).

Don't use typedef for renaming things, but merely to abbreviate declarations which are difficult to use or understand otherwise (e.g. nested STL containers, like maps of vectors and the like). But find a meaningful name! It might be more sensible to write a dedicated class with specialized access functions for such objects.

== Functions, Methods ==
'''Naming''': first word starts lower case, following words start upper case (e.g. myFancyFunction())

Provide Access to member variables of a class by Attribute functions.

Attribute functions: {{{getValue(), setValue()}}}; declare retrieving functions as const: {{{getValue() const;}}}

Boolean functions: {{{isOfColour(), hasProperty()}}}

== Documentation ==
Document classes, member functions, parameters, member variables, types, authors in the header file with Doxygen!

Document each important step in the source file. Document first of all '''why''' the line of code is there.

Give hints for possible future developments – you might be the developer!

If it is not at once clear from the code what it does, try to rewrite it in a clearer way. Only if that is not possible, explain in a comment also '''what''' it does. Put comments on closing brackets of larger code blocks (#endif, for, if, else, do, while, ...)

== Code Formatting ==
Let the beautifier run over the code. [[http://astyle.sourceforge.net/|Astyle]] has been used successfully for this task. Astyle has many settings to influence the code formatting, but doesn't influence the number of blank lines. Astyle can be steered via a steering file, that can either be made known to the system via a special environment variable or by putting it as ".astylerc" into your home directory. For details see the documentation of astyle.

An example steering file for astyle with the settings for MarlinTPC has been attached: [[attachment:astyle.cfg]] This file is equivalent to running astyle with the options

{{{
astyle -s4 -C -c -M80 -U -p -k1 -A1 -S -Y
}}}
Reduce multiple blank lines in header and source files with:

{{{cat -s file > tempfile mv tempfile file}}}

Go for good typography! Remove spaces in front of semicolons and commas as well as double semicolons with the "Find & Replace" function of your editor by searching for:

 . {{{" ;" --> ";"}}} {{{" ," --> ","}}} {{{";;" --> ";"}}}

''repeatedly'' until nothing is left over. Of course you can also try to do all of that within a shell script.

Now, consciously, format the code with blank lines:

1 blank line (where a preceding comment belongs to the block):

 * between variable declarations of different "topic"
 * before formulas
 * before code blocks
 * after namespace
 * before and after public, private, protected
 * between #include groups (have a comment here for each group, like //Marlin, //C++, //Gear)

3 blank lines:

 * before member functions in the source file

Do spell check your comments and also your source code!

Have a last good look by eye!

Again: No compiler warnings shall remain (all warnings on, pedantic mode)!

== That's it ==
You can test and then commit your code to the repository.

----
This was written by Oliver Schaefer (and copied by C.R.)