=head1 NAME

CodingStyle - standards while programming for GNU LilyPond

=head1 DESCRIPTION

We use these standards while doing programming for GNU LilyPond.  If
you do some hacking, we appreciate it if you would follow this rules,
but if you don't, we still like you.

Functions and methods do not return errorcodes, but use assert for
checking status. 

=head2 Quote:

A program should be light and agile, its subroutines
connected like a string of pearls.  The spirit and intent of
the program should be retained throughout.  There should be
neither too little nor too much, neither needless loops nor
useless variables, neither lack of structure nor overwhelming
rigidity.

A program should follow the 'Law of Least
Astonishment'.  What is this law?  It is simply that the
program should always respond to the user in the way that
astonishes him least.

A program, no matter how complex, should act as a
single unit.  The program should be directed by the logic
within rather than by outward appearances.

If the program fails in these requirements, it will be
in a state of disorder and confusion.  The only way to correct
this is to rewrite the program.

-- Geoffrey James, "The Tao of Programming"


=head2 LANGUAGES

C++, /bin/sh and python are preferred.  Perl is not.

=head2 FILES

Definitions of classes that are only accessed via pointers
(*) or references (&) shall not be included as include files.

filenames

	".hh"	Include files
	".cc"	Implementation files
	".icc"	Inline definition files
	".tcc"	non inline Template defs

in emacs:

	(setq auto-mode-alist
	      (append '(("\\.make$" . makefile-mode)
			("\\.cc$" . c++-mode)
			("\\.icc$" . c++-mode)
			("\\.tcc$" . c++-mode)
			("\\.hh$" . c++-mode)
			("\\.pod$" . text-mode)		
			)
		      auto-mode-alist))


The class Class_name_abbreviation is coded in F<class-name-abbr.*>


=head2 INDENTATION

in emacs:


	(add-hook 'c++-mode-hook
		  '(lambda() (c-set-style "gnu")
		     )
		  )

If you like using font-lock, you can also add this to your F<.emacs>:

	(setq font-lock-maximum-decoration t)
	(setq c++-font-lock-keywords-3 
	      (append
	       c++-font-lock-keywords-3
	       '(("\\b\\([a-zA-Z_]+_\\)\\b" 1 font-lock-variable-name-face)
	       ("\\b\\([A-Z]+[a-z_]+\\)\\b" 1 font-lock-type-face))
	       ))

=head2 CLASSES and TYPES:

	This_is_a_class
	AClass_name	(for Abbreviation_class_name)

=head2 MEMBERS

	Class::member()
	Type Class::member_type_
	Type Class::member_type()

the C<type> is a Hungarian notation postfix for C<Type>. See below

=head2 MACROS

Macros should be written completely in uppercase

The code should not be compilable if proper macro declarations are not
included. 

Don't laugh. It took us a whole evening/night to figure out one of
these bugs.

=head2 BROKEN CODE

Broken code (hardwired dependencies, hardwired constants, slow
algorithms and obvious limitations) should be marked as such:
either with a verbose TODO, or with a short "ugh" comment.

=head2 COMMENTS

The source is commented in the DOC++ style.  Check out doc++ at
http://www.zib.de/Visual/software/doc++/index.html

	/*
		C style comments for multiline comments.
		They come before the thing to document.
		[...]
	*/


	/**
		short description.
		Long class documentation.
		(Hungarian postfix)

		TODO Fix boring_member()
	*/
	class Class {
		/**
		  short description.
		  long description
		*/

		Data data_member_;


		/**
			short memo. long doco of member()
			@param description of arguments
			@return Rettype
		*/
		Rettype member(Argtype);

		/// memo only
		boring_member() {
			data_member_ = 121; // ugh
		}
	};


	
Unfortunately most of the code isn't really documented that good.


=head2 MEMBERS (2)

Standard methods:

	///check that *this satisfies its invariants, abort if not.
	void OK() const

	/// print *this (and substructures) to debugging log
	void print() const

	/**
	protected member. Usually invoked by non-virtual XXXX()
	*/
	virtual do_XXXX()

	/**add some data to *this.
	Presence of these methods usually imply that it is not feasible to this
	via  a constructor
	*/
	add (..)

	/// replace some data of *this
	set (..)

=head2 Constructor

Every class should have a default constructor.  

Don't use non-default constructors if this can be avoided:

	Foo f(1)

is less readable than

	Foo f;
	f.x = 1

or 
	Foo f(Foo_convert::int_to_foo (1))



=head1 HUNGARIAN NOTATION NAMING CONVENTION

Proposed is a naming convention derived from the so-called I<Hungarian
Notation>.

=head2 Hungarian

The Hungarian Notation was conceived by or at least got its name from,
the hungarian programmer Charles Simonyi.  It is a naming convention 
with the aim to make code more readable (for fellow programmers), and 
more accessible for programmers that are new to a project.

The essence of the Hungarian Notation is that every identifier has a
part which identifies its type (for functions this is the result
type).  This is particularly useful in object oriented programming,
where a particular object implies a specific interface (a set of
member functions, perhaps some redefined operators), and for
accounting heap allocated memory pointers and links.

=head2 Advantages

Another fun quote from Microsoft Secrets:


	The Hungarian naming convention gives developers the ability
	to read other people's code relatively easily, with a minmum
	number of comments in the source code.  Jon De Vann estimated
	that only about 1 percent of all lines in the Excel product
	code consist of comments, but the code is still very
	understandable due to the use of Hungarian: "if you look at
	our source code, you also notice very few comments.  Hungarian
	gives us the ability to go in and read code..."

Wow! If you use Hungarian you don't have to document your software!
Just think of the hours I have wasted documenting while this "silver bullet"
existed. I feel so stupid and ashamed!  [Didn't MMM-Brooks say `There is
no silver bullet?' --HWN]


=head2 Disadvantages

=over 5

=item *

more keystrokes (disk space!)

=item *

it looks silly C<get_slu_p()>

=item *

it looks like code from micro suckers

=item *

(which) might scare away some (otherwise good?)
progammers, or make you a paria in the free
software community

=item *

it has ambiguities

=item *

not very useful if not used consistently

=item *

usefullness in I<very large> (but how many classes is very large?)
remains an issue.

=back



=head2 Proposal

=over 5

=item *

learn about cut and paste / use emacs or vi
or lean to type using ten fingers

=item *

Use emacs dabbrev-expand, with dabbrev-case-fold-search set to nil.

=item *

use no, or pick less silly, abbrvs.

=item *

use non-ambiguous postfixes C<identifier_name_type_modifier[_modifier]>

=item *

There is no need for Hungarian if the scope of the variable is small,
ie. local variables, arguments in function definitions (not
declarations).

=back

Macros, C<enum>s and C<const>s are all uppercase,
with the parts of the names separated by underscores.

=head2 Types

=over 5

=item C<byte>


unsigned char. (The postfix _by is ambiguous)

=item C<b>


bool

=item C<bi>

bit

=item C<ch>

char

=item C<f>

float

=item C<i>

signed integer

=item C<str>

string class

=item C<sz>

Zero terminated c string

=item C<u>

unsigned integer

=back

=head2 User defined types


	/** Slur blah. blah.
	(slur)
	*/
	class Slur {};
	Slur* slur_p = new Slur;

=head2 Modifiers

The following types modify the meaning of the prefix. 
These are preceded by the prefixes:

=over 5

=item C<a>

array

=item C<array>

user built array.

=item C<c>

const. Note that the proper order is C<Type const> i.s.o. C<const Type>

=item C<C>

A const pointer. This would be equivalent to C<_c_l>, but since any
"const" pointer has to be a link (you can't delete a const pointer),
it is superfluous.

=item C<l>

temporary pointer to object (link)

=item C<p>

pointer to newed object

=item C<r>

reference

=back

=over 5

=head2 Adjective

Adjectives such as global and static should be spelled out in full.
They come before the noun that they refer to, just as in normal english.

foo_global_i: a global variable of type int commonly called "foo".

static class members do not need the static_ prefix in the name (the
Class::var notation usually makes it clear that it is static)

=item C<loop_i>

Variable loop: an integer

=item C<u>

Temporary variable: an unsigned integer

=item C<test_ch>

Variable test: a character

=item C<first_name_str>

Variable first_name: a String class object

=item C<last_name_ch_a>

Variable last_name: a C<char> array

=item C<foo_i_p>

Variable foo: an C<Int*> that you must delete

=item C<bar_i_l>

Variable bar: an C<Int*> that you must not delete

=back

Generally default arguments are taboo, except for nil pointers.

The naming convention can be quite conveniently memorised, by
expressing the type in english, and abbreviating it

	static Array<int*> foo

C<foo> can be described as "the static int-pointer user-array", so you get

	foo_static_l_arr
	



=head1 MISCELLANEOUS

For some tasks, some scripts are supplied, notably creating patches, a
mirror of the website, generating the header to put over cc and hh
files, doing a release.

Use them.

The following generic identifications are used:

	up == 1
	left == -1
	right == 1
	down == -1

Intervals are pictured lying on a horizontal numberline (Interval[-1]
is the minimum). The 2D plane has +x on the right, +y pointing up.