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Chris Lattner	d80c43c	2001-07-09 03:27:08 +0000	[diff] [blame]	1	<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
				2	<html><head><title>A Few Coding Standards</title></head>
				3	<body bgcolor=white>
				4
				5	<table width="100%" bgcolor="#330077" border=0 cellpadding=4 cellspacing=0>
				6	<tr><td>  <font size=+5 color="#EEEEFF" face="Georgia,Palatino,Times,Roman"><b>A Few Coding Standards</b></font></td>
				7	</tr></table>
				8
				9	<ol>
				10	<li><a href="#introduction">Introduction</a>
Chris Lattner	7ae36bb	2001-07-23 20:40:41 +0000	[diff] [blame]	11	<li><a href="#mechanicalissues">Mechanical Source Issues</a>
Chris Lattner	d80c43c	2001-07-09 03:27:08 +0000	[diff] [blame]	12	<ol>
				13	<li><a href="#sourceformating">Source Code Formatting</a>
				14	<ol>
				15	<li><a href="#scf_commenting">Commenting</a>
				16	<li><a href="#scf_commentformat">Comment Formatting</a>
Chris Lattner	2e5cbc2	2003-08-07 21:45:47 +0000	[diff] [blame]	17	<li><a href="#scf_includes">#include Style</a>
Chris Lattner	d80c43c	2001-07-09 03:27:08 +0000	[diff] [blame]	18	<li><a href="#scf_codewidth">Source Code Width</a>
				19	<li><a href="#scf_spacestabs">Use Spaces Instead of Tabs</a>
				20	<li><a href="#scf_indentation">Indent Code Consistently</a>
				21	</ol>
				22	<li><a href="#compilerissues">Compiler Issues</a>
				23	<ol>
				24	<li><a href="#ci_warningerrors">Treat Compiler Warnings Like Errors</a>
				25	<li><a href="#ci_cpp_features">Which C++ features can I use?</a>
				26	<li><a href="#ci_portable_code">Write Portable Code</a>
				27	</ol>
				28	</ol>
				29	<li><a href="#styleissues">Style Issues</a>
				30	<ol>
				31	<li><a href="#macro">The High Level Issues</a>
				32	<ol>
				33	<li><a href="#hl_module">A Public Header File <b>is</b> a Module</a>
				34	<li><a href="#hl_dontinclude">#include as Little as Possible</a>
				35	<li><a href="#hl_privateheaders">Keep "internal" Headers Private</a>
				36	</ol>
				37	<li><a href="#micro">The Low Level Issues</a>
				38	<ol>
				39	<li><a href="#hl_assert">Assert Liberally</a>
				40	<li><a href="#hl_preincrement">Prefer Preincrement</a>
Chris Lattner	13c4659	2002-01-20 19:01:26 +0000	[diff] [blame]	41	<li><a href="#hl_avoidendl">Avoid endl</a>
Chris Lattner	d80c43c	2001-07-09 03:27:08 +0000	[diff] [blame]	42	<li><a href="#hl_exploitcpp">Exploit C++ to its Fullest</a>
				43	</ol>
				44	<li><a href="#iterators">Writing Iterators</a>
				45	</ol>
				46	<li><a href="#seealso">See Also</a>
				47	</ol><p>
				48
				49
				50	<!-- *********************************************************************** -->
				51	</ul><table width="100%" bgcolor="#330077" border=0 cellpadding=4 cellspacing=0><tr><td align=center><font color="#EEEEFF" size=+2 face="Georgia,Palatino"><b>
				52	<a name="introduction">Introduction
				53	</b></font></td></tr></table><ul>
				54	<!-- *********************************************************************** -->
				55
Misha Brukman	1b36d67	2003-10-06 19:26:00 +0000	[diff] [blame]	56	This document attempts to describe a few coding standards that are being used in
				57	the LLVM source tree. Although no coding standards should be regarded as
				58	absolute requirements to be followed in all instances, coding standards can be
				59	useful.<p>
Chris Lattner	d80c43c	2001-07-09 03:27:08 +0000	[diff] [blame]	60
Misha Brukman	1b36d67	2003-10-06 19:26:00 +0000	[diff] [blame]	61	This document intentionally does not prescribe fixed standards for religious
				62	issues such as brace placement and space usage. For issues like this, follow
				63	the golden rule:
Chris Lattner	d80c43c	2001-07-09 03:27:08 +0000	[diff] [blame]	64
				65	<a name="goldenrule">
Misha Brukman	1b36d67	2003-10-06 19:26:00 +0000	[diff] [blame]	66	<blockquote><b>If you are adding a significant body of source to a project, feel
				67	free to use whatever style you are most comfortable with. If you are extending,
				68	enhancing, or bug fixing already implemented code, use the style that is already
				69	being used so that the source is uniform and easy to follow.</b></blockquote>
Chris Lattner	d80c43c	2001-07-09 03:27:08 +0000	[diff] [blame]	70
Misha Brukman	1b36d67	2003-10-06 19:26:00 +0000	[diff] [blame]	71	The ultimate goal of these guidelines is the increase readability and
				72	maintainability of our common source base. If you have suggestions for topics to
				73	be included, please mail them to <a href="mailto:sabre@nondot.org">Chris</a>.<p>
Chris Lattner	d80c43c	2001-07-09 03:27:08 +0000	[diff] [blame]	74
				75
				76	<!-- *********************************************************************** -->
				77	</ul><table width="100%" bgcolor="#330077" border=0 cellpadding=4 cellspacing=0><tr><td align=center><font color="#EEEEFF" size=+2 face="Georgia,Palatino"><b>
				78	<a name="mechanicalissues">Mechanical Source Issues
				79	</b></font></td></tr></table><ul>
				80	<!-- *********************************************************************** -->
				81
				82	<!-- ======================================================================= -->
				83	</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0><tr><td> </td><td width="100%">  <font color="#EEEEFF" face="Georgia,Palatino"><b>
				84	<a name="sourceformating">Source Code Formatting
				85	</b></font></td></tr></table><ul>
				86
				87
				88	<!-- _______________________________________________________________________ -->
				89	</ul><a name="scf_commenting"><h4><hr size=0>Commenting</h4><ul>
				90
Misha Brukman	1b36d67	2003-10-06 19:26:00 +0000	[diff] [blame]	91	Comments are one critical part of readability and maintainability. Everyone
				92	knows they should comment, so should you. :) Although we all should probably
				93	comment our code more than we do, there are a few very critical places that
				94	documentation is very useful:<p>
Chris Lattner	d80c43c	2001-07-09 03:27:08 +0000	[diff] [blame]	95
				96	<ol>
				97	<h4><li>File Headers</h4>
Misha Brukman	1b36d67	2003-10-06 19:26:00 +0000	[diff] [blame]	98	Every source file should have a header on it that describes the basic purpose of
				99	the file. If a file does not have a header, it should not be checked into CVS.
				100	Most source trees will probably have a standard file header format. The
				101	standard format for the LLVM source tree looks like this:<p>
Chris Lattner	d80c43c	2001-07-09 03:27:08 +0000	[diff] [blame]	102
				103	<pre>
Chris Lattner	c49fcd1	2003-10-13 14:58:11 +0000	[diff] [blame]	104	//===-- llvm/Instruction.h - Instruction class definition -------- C++ --===//
Chris Lattner	d80c43c	2001-07-09 03:27:08 +0000	[diff] [blame]	105	//
				106	// This file contains the declaration of the Instruction class, which is the
				107	// base class for all of the VM instructions.
				108	//
				109	//===----------------------------------------------------------------------===//
				110	</pre>
				111
Misha Brukman	1b36d67	2003-10-06 19:26:00 +0000	[diff] [blame]	112	A few things to note about this particular format. The "<tt>-- C++ --</tt>"
				113	string on the first line is there to tell Emacs that the source file is a C++
				114	file, not a C file (Emacs assumes .h files are C files by default [Note that tag
				115	this is not necessary in .cpp files]). The name of the file is also on the
				116	first line, along with a very short description of the purpose of the file.
				117	This is important when printing out code and flipping though lots of pages.<p>
Chris Lattner	d80c43c	2001-07-09 03:27:08 +0000	[diff] [blame]	118
Misha Brukman	1b36d67	2003-10-06 19:26:00 +0000	[diff] [blame]	119	The main body of the description does not have to be very long in most cases.
				120	Here it's only two lines. If an algorithm is being implemented or something
				121	tricky is going on, a reference to the paper where it is published should be
				122	included, as well as any notes or "gotchas" in the code to watch out for.<p>
Chris Lattner	d80c43c	2001-07-09 03:27:08 +0000	[diff] [blame]	123
				124
				125	<h4><li>Class overviews</h4>
				126
Misha Brukman	1b36d67	2003-10-06 19:26:00 +0000	[diff] [blame]	127	Classes are one fundemental part of a good object oriented design. As such, a
				128	class definition should have a comment block that explains what the class is
				129	used for... if it's not obvious. If it's so completely obvious your grandma
				130	could figure it out, it's probably safe to leave it out. Naming classes
				131	something sane goes a long ways towards avoiding writing documentation. :)<p>
Chris Lattner	d80c43c	2001-07-09 03:27:08 +0000	[diff] [blame]	132
				133
				134	<h4><li>Method information</h4>
				135
Misha Brukman	1b36d67	2003-10-06 19:26:00 +0000	[diff] [blame]	136	Methods defined in a class (as well as any global functions) should also be
				137	documented properly. A quick note about what it does any a description of the
				138	borderline behaviour is all that is necessary here (unless something
				139	particularly tricky or insideous is going on). The hope is that people can
				140	figure out how to use your interfaces without reading the code itself... that is
				141	the goal metric.<p>
Chris Lattner	d80c43c	2001-07-09 03:27:08 +0000	[diff] [blame]	142
Misha Brukman	1b36d67	2003-10-06 19:26:00 +0000	[diff] [blame]	143	Good things to talk about here are what happens when something unexpected
				144	happens: does the method return null? Abort? Format your hard disk?<p>
Chris Lattner	d80c43c	2001-07-09 03:27:08 +0000	[diff] [blame]	145	</ol>
				146
				147
				148	<!-- _______________________________________________________________________ -->
				149	</ul><a name="scf_commentformat"><h4><hr size=0>Comment Formatting</h4><ul>
				150
Misha Brukman	1b36d67	2003-10-06 19:26:00 +0000	[diff] [blame]	151	In general, prefer C++ style (<tt>//</tt>) comments. They take less space,
				152	require less typing, don't have nesting problems, etc. There are a few cases
				153	when it is useful to use C style (<tt>/* */</tt>) comments however:<p>
Chris Lattner	d80c43c	2001-07-09 03:27:08 +0000	[diff] [blame]	154
				155	<ol>
Misha Brukman	1b36d67	2003-10-06 19:26:00 +0000	[diff] [blame]	156	<li>When writing a C code: Obviously if you are writing C code, use C style
				157	comments. :)
Chris Lattner	d80c43c	2001-07-09 03:27:08 +0000	[diff] [blame]	158	<li>When writing a header file that may be #included by a C source file.
Misha Brukman	1b36d67	2003-10-06 19:26:00 +0000	[diff] [blame]	159	<li>When writing a source file that is used by a tool that only accepts C style
				160	comments.
Chris Lattner	d80c43c	2001-07-09 03:27:08 +0000	[diff] [blame]	161	</ol><p>
				162
Misha Brukman	1b36d67	2003-10-06 19:26:00 +0000	[diff] [blame]	163	To comment out a large block of code, use <tt>#if 0</tt> and <tt>#endif</tt>.
				164	These nest properly and are better behaved in general than C style comments.<p>
Chris Lattner	d80c43c	2001-07-09 03:27:08 +0000	[diff] [blame]	165
Chris Lattner	2e5cbc2	2003-08-07 21:45:47 +0000	[diff] [blame]	166	<!-- _______________________________________________________________________ -->
				167	</ul><a name="scf_includes"><h4><hr size=0>#include Style</h4><ul>
				168
				169	Immediately after the <a href="#scf_commenting">header file comment</a> (and
				170	include guards if working on a header file), the <a
				171	href="hl_dontinclude">minimal</a> list of #includes required by the file should
				172	be listed. We prefer these #includes to be listed in this order:<p>
				173
				174	<ol>
				175	<li><a href="#mmheader">Main Module header</a>
				176	<li><a href="#hl_privateheaders">Local/Private Headers</a>
				177	<li>llvm/*
				178	<li>llvm/Analysis/*
				179	<li>llvm/Assembly/*
				180	<li>llvm/Bytecode/*
				181	<li>llvm/CodeGen/*
				182	<li>...
				183	<li>Support/*
				184	<li>Config/*
				185	<li>System #includes
				186	</ol>
				187
				188	... and each catagory should be sorted by name.<p>
				189
				190	<a name="mmheader">The "Main Module Header" file applies to .cpp file which
				191	implement an interface defined by a .h file. This #include should always be
				192	included <b>first</b> regardless of where it lives on the file system. By
				193	including a header file first in the .cpp files that implement the interfaces,
				194	we ensure that the header does not have any hidden dependencies which are not
				195	explicitly #included in the header, but should be. It is also a form of
				196	documentation in the .cpp file to indicate where the interfaces it implements
				197	are defined.<p>
				198
Chris Lattner	d80c43c	2001-07-09 03:27:08 +0000	[diff] [blame]	199
				200	<!-- _______________________________________________________________________ -->
				201	</ul><a name="scf_codewidth"><h4><hr size=0>Source Code Width</h4><ul>
				202
				203	Write your code to fit within 80 columns of text. This helps those of us who like to print out code and look at your code in an xterm without resizing it.
				204
				205
				206	<!-- _______________________________________________________________________ -->
				207	</ul><a name="scf_spacestabs"><h4><hr size=0>Use Spaces Instead of Tabs</h4><ul>
				208
Misha Brukman	1b36d67	2003-10-06 19:26:00 +0000	[diff] [blame]	209	In all cases, prefer spaces to tabs in source files. People have different
				210	prefered indentation levels, and different styles of indentation that they
				211	like... this is fine. What isn't is that different editors/viewers expand tabs
				212	out to different tab stops. This can cause your code to look completely
				213	unreadable, and it is not worth dealing with.<p>
Chris Lattner	d80c43c	2001-07-09 03:27:08 +0000	[diff] [blame]	214
Misha Brukman	1b36d67	2003-10-06 19:26:00 +0000	[diff] [blame]	215	As always, follow the <a href="#goldenrule">Golden Rule</a> above: follow the
				216	style of existing code if your are modifying and extending it. If you like four
				217	spaces of indentation, <b>DO NOT</b> do that in the middle of a chunk of code
				218	with two spaces of indentation. Also, do not reindent a whole source file: it
				219	makes for incredible diffs that are absolutely worthless.<p>
Chris Lattner	d80c43c	2001-07-09 03:27:08 +0000	[diff] [blame]	220
				221
				222	<!-- _______________________________________________________________________ -->
				223	</ul><a name="scf_indentation"><h4><hr size=0>Indent Code Consistently</h4><ul>
				224
Misha Brukman	1b36d67	2003-10-06 19:26:00 +0000	[diff] [blame]	225	Okay, your first year of programming you were told that indentation is
				226	important. If you didn't believe and internalize this then, now is the time.
				227	Just do it.<p>
Chris Lattner	d80c43c	2001-07-09 03:27:08 +0000	[diff] [blame]	228
				229
				230
				231
				232	<!-- ======================================================================= -->
				233	</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0><tr><td> </td><td width="100%">  <font color="#EEEEFF" face="Georgia,Palatino"><b>
				234	<a name="compilerissues">Compiler Issues
				235	</b></font></td></tr></table><ul>
				236
				237
				238	<!-- _______________________________________________________________________ -->
				239	</ul><a name="ci_warningerrors"><h4><hr size=0>Treat Compiler Warnings Like Errors</h4><ul>
				240
Misha Brukman	1b36d67	2003-10-06 19:26:00 +0000	[diff] [blame]	241	If your code has compiler warnings in it, something is wrong: you aren't casting
				242	values correctly, your have "questionable" constructs in your code, or you are
				243	doing something legitimately wrong. Compiler warnings can cover up legitimate
				244	errors in output and make dealing with a translation unit difficult.<p>
Chris Lattner	d80c43c	2001-07-09 03:27:08 +0000	[diff] [blame]	245
Misha Brukman	1b36d67	2003-10-06 19:26:00 +0000	[diff] [blame]	246	It is not possible to prevent all warnings from all compilers, nor is it
				247	desirable. Instead, pick a standard compiler (like <tt>gcc</tt>) that provides
				248	a good thorough set of warnings, and stick to them. At least in the case of
				249	<tt>gcc</tt>, it is possible to work around any spurious errors by changing the
				250	syntax of the code slightly. For example, an warning that annoys me occurs when
				251	I write code like this:<p>
Chris Lattner	d80c43c	2001-07-09 03:27:08 +0000	[diff] [blame]	252
				253	<pre>
				254	if (V = getValue()) {
				255	..
				256	}
				257	</pre><p>
				258
Misha Brukman	1b36d67	2003-10-06 19:26:00 +0000	[diff] [blame]	259	<tt>gcc</tt> will warn me that I probably want to use the <tt>==</tt> operator,
				260	and that I probably mistyped it. In most cases, I haven't, and I really don't
				261	want the spurious errors. To fix this particular problem, I rewrite the code
				262	like this:<p>
Chris Lattner	d80c43c	2001-07-09 03:27:08 +0000	[diff] [blame]	263
				264	<pre>
				265	if ((V = getValue())) {
				266	..
				267	}
				268	</pre><p>
				269
Misha Brukman	2d10d75	2003-07-28 21:57:18 +0000	[diff] [blame]	270	...which shuts <tt>gcc</tt> up. Any <tt>gcc</tt> warning that annoys you can be
				271	fixed by massaging the code appropriately.<p>
Chris Lattner	d80c43c	2001-07-09 03:27:08 +0000	[diff] [blame]	272
Misha Brukman	2d10d75	2003-07-28 21:57:18 +0000	[diff] [blame]	273	These are the <tt>gcc</tt> warnings that I prefer to enable: <tt>-Wall -Winline
				274	-W -Wwrite-strings -Wno-unused</tt><p>
Chris Lattner	d80c43c	2001-07-09 03:27:08 +0000	[diff] [blame]	275
				276
				277	<!-- _______________________________________________________________________ -->
				278	</ul><a name="ci_cpp_features"><h4><hr size=0>Which C++ features can I use?</h4><ul>
				279
Misha Brukman	2d10d75	2003-07-28 21:57:18 +0000	[diff] [blame]	280	Compilers are finally catching up to the C++ standard. Most compilers implement
				281	most features, so you can use just about any features that you would like. In
				282	the LLVM source tree, I have chosen to not use these features:<p>
Chris Lattner	d80c43c	2001-07-09 03:27:08 +0000	[diff] [blame]	283
				284	<ol>
Misha Brukman	2d10d75	2003-07-28 21:57:18 +0000	[diff] [blame]	285	<li>Exceptions: Exceptions are very useful for error reporting and handling
				286	exceptional conditions. I do not use them in LLVM because they do have an
				287	associated performance impact (by restricting restructuring of code), and parts
				288	of LLVM are designed for performance critical purposes.<p>
Chris Lattner	d80c43c	2001-07-09 03:27:08 +0000	[diff] [blame]	289
Misha Brukman	2d10d75	2003-07-28 21:57:18 +0000	[diff] [blame]	290	Just like most of the rules in this document, this isn't a hard and fast
				291	requirement. Exceptions are used in the Parser, because it simplifies error
				292	reporting <b>significantly</b>, and the LLVM parser is not at all in the
				293	critical path.<p>
Chris Lattner	d80c43c	2001-07-09 03:27:08 +0000	[diff] [blame]	294
Misha Brukman	2d10d75	2003-07-28 21:57:18 +0000	[diff] [blame]	295	<li>RTTI: RTTI has a large cost in terms of executable size, and compilers are
				296	not yet very good at stomping out "dead" class information blocks. Because of
				297	this, typeinfo and dynamic cast are not used.
Chris Lattner	d80c43c	2001-07-09 03:27:08 +0000	[diff] [blame]	298	</ol><p>
				299
Misha Brukman	2d10d75	2003-07-28 21:57:18 +0000	[diff] [blame]	300	Other features, such as templates (without partial specialization) can be used
				301	freely. The general goal is to have clear, consise, performant code... if a
				302	technique assists with that then use it.<p>
Chris Lattner	d80c43c	2001-07-09 03:27:08 +0000	[diff] [blame]	303
				304
				305	<!-- _______________________________________________________________________ -->
				306	</ul><a name="ci_portable_code"><h4><hr size=0>Write Portable Code</h4><ul>
				307
Misha Brukman	2d10d75	2003-07-28 21:57:18 +0000	[diff] [blame]	308	In almost all cases, it is possible and within reason to write completely
				309	portable code. If there are cases where it isn't possible to write portable
				310	code, isolate it behind a well defined (and well documented) interface.<p>
Chris Lattner	d80c43c	2001-07-09 03:27:08 +0000	[diff] [blame]	311
Misha Brukman	2d10d75	2003-07-28 21:57:18 +0000	[diff] [blame]	312	In practice, this means that you shouldn't assume much about the host compiler,
				313	including its support for "high tech" features like partial specialization of
				314	templates. In fact, Visual C++ 6 could be an important target for our work in
				315	the future, and we don't want to have to rewrite all of our code to support
				316	it.<p>
Chris Lattner	d80c43c	2001-07-09 03:27:08 +0000	[diff] [blame]	317
				318
				319
				320	<!-- *********************************************************************** -->
				321	</ul><table width="100%" bgcolor="#330077" border=0 cellpadding=4 cellspacing=0><tr><td align=center><font color="#EEEEFF" size=+2 face="Georgia,Palatino"><b>
				322	<a name="styleissues">Style Issues
				323	</b></font></td></tr></table><ul>
				324	<!-- *********************************************************************** -->
				325
				326
				327	<!-- ======================================================================= -->
				328	</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0><tr><td> </td><td width="100%">  <font color="#EEEEFF" face="Georgia,Palatino"><b>
				329	<a name="macro">The High Level Issues
				330	</b></font></td></tr></table><ul>
				331
				332
				333	<!-- _______________________________________________________________________ -->
				334	</ul><a name="hl_module"><h4><hr size=0>A Public Header File <b>is</b> a Module</h4><ul>
				335
Misha Brukman	2d10d75	2003-07-28 21:57:18 +0000	[diff] [blame]	336	C++ doesn't do too well in the modularity department. There is no real
				337	encapsulation or data hiding (unless you use expensive protocol classes), but it
				338	is what we have to work with. When you write a public header file (in the LLVM
				339	source tree, they live in the top level "include" directory), you are defining a
				340	module of functionality.<p>
Chris Lattner	d80c43c	2001-07-09 03:27:08 +0000	[diff] [blame]	341
Misha Brukman	2d10d75	2003-07-28 21:57:18 +0000	[diff] [blame]	342	Ideally, modules should be completely independent of each other, and their
				343	header files should only include the absolute minimum number of headers
				344	possible. A module is not just a class, a function, or a namespace: <a
				345	href="http://www.cuj.com/articles/2000/0002/0002c/0002c.htm">it's a collection
				346	of these</a> that defines an interface. This interface may be several
				347	functions, classes or data structures, but the important issue is how they work
				348	together.<p>
Chris Lattner	d80c43c	2001-07-09 03:27:08 +0000	[diff] [blame]	349
Misha Brukman	2d10d75	2003-07-28 21:57:18 +0000	[diff] [blame]	350	In general, a module should be implemented with one or more <tt>.cpp</tt> files.
				351	Each of these <tt>.cpp</tt> files should include the header that defines their
				352	interface first. This ensure that all of the dependences of the module header
				353	have been properly added to the module header itself, and are not implicit.
				354	System headers should be included after user headers for a translation unit.<p>
Chris Lattner	d80c43c	2001-07-09 03:27:08 +0000	[diff] [blame]	355
				356
				357	<!-- _______________________________________________________________________ -->
				358	</ul><a name="hl_dontinclude"><h4><hr size=0>#include as Little as Possible</h4><ul>
				359
Misha Brukman	2d10d75	2003-07-28 21:57:18 +0000	[diff] [blame]	360	<tt>#include</tt> hurts compile time performance. Don't do it unless you have
				361	to, especially in header files.<p>
Chris Lattner	d80c43c	2001-07-09 03:27:08 +0000	[diff] [blame]	362
Misha Brukman	2d10d75	2003-07-28 21:57:18 +0000	[diff] [blame]	363	But wait, sometimes you need to have the definition of a class to use it, or to
				364	inherit from it. In these cases go ahead and #include that header file. Be
				365	aware however that there are many cases where you don't need to have the full
				366	definition of a class. If you are using a pointer or reference to a class, you
				367	don't need the header file. If you are simply returning a class instance from a
				368	prototyped function or method, you don't need it. In fact, for most cases, you
				369	simply don't need the definition of a class... and not <tt>#include</tt>'ing
				370	speeds up compilation.<p>
Chris Lattner	d80c43c	2001-07-09 03:27:08 +0000	[diff] [blame]	371
Misha Brukman	2d10d75	2003-07-28 21:57:18 +0000	[diff] [blame]	372	It is easy to try to go too overboard on this recommendation, however. You
				373	<b>must</b> include all of the header files that you are using, either directly
				374	or indirectly (through another header file). To make sure that you don't
				375	accidently forget to include a header file in your module header, make sure to
				376	include your module header <b>first</b> in the implementation file (as mentioned
				377	above). This way there won't be any hidden dependencies that you'll find out
				378	about later...<p>
Chris Lattner	d80c43c	2001-07-09 03:27:08 +0000	[diff] [blame]	379
				380
				381	<!-- _______________________________________________________________________ -->
				382	</ul><a name="hl_privateheaders"><h4><hr size=0>Keep "internal" Headers Private</h4><ul>
				383
Misha Brukman	2d10d75	2003-07-28 21:57:18 +0000	[diff] [blame]	384	Many modules have a complex implementation that causes them to use more than one
				385	implementation (<tt>.cpp</tt>) file. It is often tempting to put the internal
				386	communication interface (helper classes, extra functions, etc) in the public
				387	module header file. Don't do this. :)<p>
Chris Lattner	d80c43c	2001-07-09 03:27:08 +0000	[diff] [blame]	388
Misha Brukman	2d10d75	2003-07-28 21:57:18 +0000	[diff] [blame]	389	If you really need to do something like this, put a private header file in the
				390	same directory as the source files, and include it locally. This ensures that
				391	your private interface remains private and undisturbed by outsiders.<p>
Chris Lattner	d80c43c	2001-07-09 03:27:08 +0000	[diff] [blame]	392
Misha Brukman	2d10d75	2003-07-28 21:57:18 +0000	[diff] [blame]	393	Note however, that it's okay to put extra implementation methods a public class
				394	itself... just make them private (or protected), and all is well.<p>
Chris Lattner	d80c43c	2001-07-09 03:27:08 +0000	[diff] [blame]	395
				396
				397	<!-- ======================================================================= -->
				398	</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0><tr><td> </td><td width="100%">  <font color="#EEEEFF" face="Georgia,Palatino"><b>
				399	<a name="micro">The Low Level Issues
				400	</b></font></td></tr></table><ul>
				401
				402
				403	<!-- _______________________________________________________________________ -->
				404	</ul><a name="hl_assert"><h4><hr size=0>Assert Liberally</h4><ul>
				405
Misha Brukman	2d10d75	2003-07-28 21:57:18 +0000	[diff] [blame]	406	Use the "<tt>assert</tt>" function to its fullest. Check all of your
				407	preconditions and assumptions, you never know when a bug (not neccesarily even
				408	yours) might be caught early by an assertion, which reduces debugging time
				409	dramatically. The "<tt><cassert></tt>" header file is probably already
				410	included by the header files you are using, so it doesn't cost anything to use
				411	it.<p>
Chris Lattner	d80c43c	2001-07-09 03:27:08 +0000	[diff] [blame]	412
Misha Brukman	2d10d75	2003-07-28 21:57:18 +0000	[diff] [blame]	413	To further assist with debugging, make sure to put some kind of error message in
				414	the assertion statement (which is printed if the assertion is tripped). This
				415	helps the poor debugging make sense of why an assertion is being made and
				416	enforced, and hopefully what to do about it. Here is one complete example:<p>
Chris Lattner	d80c43c	2001-07-09 03:27:08 +0000	[diff] [blame]	417
				418	<pre>
				419	inline Value *getOperand(unsigned i) {
Chris Lattner	b00c582	2001-10-02 03:41:24 +0000	[diff] [blame]	420	assert(i < Operands.size() && "getOperand() out of range!");
Chris Lattner	d80c43c	2001-07-09 03:27:08 +0000	[diff] [blame]	421	return Operands[i];
				422	}
				423	</pre>
				424
				425	Here are some examples:
				426
				427	<pre>
Chris Lattner	b00c582	2001-10-02 03:41:24 +0000	[diff] [blame]	428	assert(Ty->isPointerType() && "Can't allocate a non pointer type!");
Chris Lattner	d80c43c	2001-07-09 03:27:08 +0000	[diff] [blame]	429
				430	assert((Opcode == Shl \|\| Opcode == Shr) && "ShiftInst Opcode invalid!");
				431
Chris Lattner	b00c582	2001-10-02 03:41:24 +0000	[diff] [blame]	432	assert(idx < getNumSuccessors() && "Successor # out of range!");
Chris Lattner	d80c43c	2001-07-09 03:27:08 +0000	[diff] [blame]	433
				434	assert(V1.getType() == V2.getType() && "Constant types must be identical!");
				435
Chris Lattner	b00c582	2001-10-02 03:41:24 +0000	[diff] [blame]	436	assert(isa<PHINode>(Succ->front()) && "Only works on PHId BBs!");
Chris Lattner	d80c43c	2001-07-09 03:27:08 +0000	[diff] [blame]	437	</pre><p>
				438
				439	You get the idea...<p>
				440
				441
				442	<!-- _______________________________________________________________________ -->
				443	</ul><a name="hl_preincrement"><h4><hr size=0>Prefer Preincrement</h4><ul>
				444
Misha Brukman	2d10d75	2003-07-28 21:57:18 +0000	[diff] [blame]	445	Hard fast rule: Preincrement (++X) may be no slower than postincrement (X++) and
				446	could very well be a lot faster than it. Use preincrementation whenever
				447	possible.<p>
Chris Lattner	d80c43c	2001-07-09 03:27:08 +0000	[diff] [blame]	448
Misha Brukman	2d10d75	2003-07-28 21:57:18 +0000	[diff] [blame]	449	The semantics of postincrement include making a copy of the value being
				450	incremented, returning it, and then preincrementing the "work value". For
				451	primitive types, this isn't a big deal... but for iterators, it can be a huge
				452	issue (for example, some iterators contains stack and set objects in them...
				453	copying an iterator could invoke the copy ctor's of these as well). In general,
				454	get in the habit of always using preincrement, and you won't have a problem.<p>
Chris Lattner	d80c43c	2001-07-09 03:27:08 +0000	[diff] [blame]	455
				456
				457	<!-- _______________________________________________________________________ -->
Chris Lattner	13c4659	2002-01-20 19:01:26 +0000	[diff] [blame]	458	</ul><a name="hl_avoidendl"><h4><hr size=0>Avoid endl</h4><ul>
				459
Misha Brukman	2d10d75	2003-07-28 21:57:18 +0000	[diff] [blame]	460	The <tt>endl</tt> modifier, when used with iostreams outputs a newline to the
				461	output stream specified. In addition to doing this, however, it also flushes
				462	the output stream. In other words, these are equivalent:<p>
Chris Lattner	13c4659	2002-01-20 19:01:26 +0000	[diff] [blame]	463
				464	<pre>
				465	cout << endl;
				466	cout << "\n" << flush;
				467	</pre>
				468
				469	Most of the time, you probably have no reason to flush the output stream, so it's better to use a literal <tt>"\n"</tt>.<p>
				470
				471
				472	<!-- _______________________________________________________________________ -->
Chris Lattner	d80c43c	2001-07-09 03:27:08 +0000	[diff] [blame]	473	</ul><a name="hl_exploitcpp"><h4><hr size=0>Exploit C++ to its Fullest</h4><ul>
				474
Misha Brukman	2d10d75	2003-07-28 21:57:18 +0000	[diff] [blame]	475	C++ is a powerful language. With a firm grasp on its capabilities, you can make
				476	write effective, consise, readable and maintainable code all at the same time.
				477	By staying consistent, you reduce the amount of special cases that need to be
				478	remembered. Reducing the total number of lines of code you write is a good way
				479	to avoid documentation, and avoid giving bugs a place to hide.<p>
Chris Lattner	d80c43c	2001-07-09 03:27:08 +0000	[diff] [blame]	480
Misha Brukman	2d10d75	2003-07-28 21:57:18 +0000	[diff] [blame]	481	For these reasons, come to know and love the contents of your local
				482	<algorithm> header file. Know about <functional> and what it can do
				483	for you. C++ is just a tool that wants you to master it. :)<p>
Chris Lattner	d80c43c	2001-07-09 03:27:08 +0000	[diff] [blame]	484
				485
				486
				487	<!-- ======================================================================= -->
				488	</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0><tr><td> </td><td width="100%">  <font color="#EEEEFF" face="Georgia,Palatino"><b>
				489	<a name="iterators">Writing Iterators
				490	</b></font></td></tr></table><ul>
				491
Misha Brukman	1b36d67	2003-10-06 19:26:00 +0000	[diff] [blame]	492	Here's a pretty good summary of how to write your own data structure iterators
				493	in a way that is compatible with the STL, and with a lot of other code out there
				494	(slightly edited by Chris):<p>
Chris Lattner	d80c43c	2001-07-09 03:27:08 +0000	[diff] [blame]	495
				496	<pre>
				497	From: Ross Smith <ross.s@ihug.co.nz>
				498	Newsgroups: comp.lang.c++.moderated
				499	Subject: Writing iterators (was: Re: Non-template functions that take iterators)
				500	Date: 28 Jun 2001 12:07:10 -0400
				501
				502	Andre Majorel wrote:
				503	> Any pointers handy on "writing STL-compatible iterators for
				504	> dummies ?"
				505
				506	I'll give it a try...
				507
				508	The usual situation requiring user-defined iterators is that you have
				509	a type that bears some resemblance to an STL container, and you want
				510	to provide iterators so it can be used with STL algorithms. You need
				511	to ask three questions:
				512
				513	First, is this simply a wrapper for an underlying collection of
				514	objects that's held somewhere as a real STL container, or is it a
				515	"virtual container" for which iteration is (under the hood) more
				516	complicated than simply incrementing some underlying iterator (or
				517	pointer or index or whatever)? In the former case you can frequently
				518	get away with making your container's iterators simply typedefs for
				519	those of the underlying container; your begin() function would call
				520	member_container.begin(), and so on.
				521
				522	Second, do you only need read-only iterators, or do you need separate
				523	read-only (const) and read-write (non-const) iterators?
				524
				525	Third, which kind of iterator (input, output, forward, bidirectional,
				526	or random access) is appropriate? If you're familiar with the
				527	properties of the iterator types (if not, visit
				528	<a href="http://www.sgi.com/tech/stl/">http://www.sgi.com/tech/stl/</a>), the appropriate choice should be
				529	obvious from the semantics of the container.
				530
				531	I'll start with forward iterators, as the simplest case that's likely
				532	to come up in normal code. Input and output iterators have some odd
				533	properties and rarely need to be implemented in user code; I'll leave
				534	them out of discussion. Bidirectional and random access iterators are
				535	covered below.
				536
				537	The exact behaviour of a forward iterator is spelled out in the
				538	Standard in terms of a set of expressions with specified behaviour,
				539	rather than a set of member functions, which leaves some leeway in how
				540	you actually implement it. Typically it looks something like this
				541	(I'll start with the const-iterator-only situation):
				542
Chris Lattner	2e5cbc2	2003-08-07 21:45:47 +0000	[diff] [blame]	543	#include <iterator>
Chris Lattner	d80c43c	2001-07-09 03:27:08 +0000	[diff] [blame]	544
				545	class container {
				546	public:
				547	typedef something_or_other value_type;
				548	class const_iterator:
Chris Lattner	2e5cbc2	2003-08-07 21:45:47 +0000	[diff] [blame]	549	public std::iterator<std::forward_iterator_tag, value_type> {
Chris Lattner	d80c43c	2001-07-09 03:27:08 +0000	[diff] [blame]	550	friend class container;
				551	public:
Chris Lattner	f7235cd	2003-04-23 16:25:38 +0000	[diff] [blame]	552	const value_type& operator*() const;
Chris Lattner	d80c43c	2001-07-09 03:27:08 +0000	[diff] [blame]	553	const value_type* operator->() const;
Chris Lattner	f7235cd	2003-04-23 16:25:38 +0000	[diff] [blame]	554	const_iterator& operator++();
Chris Lattner	d80c43c	2001-07-09 03:27:08 +0000	[diff] [blame]	555	const_iterator operator++(int);
				556	friend bool operator==(const_iterator lhs,
				557	const_iterator rhs);
				558	friend bool operator!=(const_iterator lhs,
				559	const_iterator rhs);
				560	private:
				561	//...
				562	};
				563	//...
				564	};
				565
				566	An iterator should always be derived from an instantiation of the
				567	std::iterator template. The iterator's life cycle functions
				568	(constructors, destructor, and assignment operator) aren't declared
				569	here; in most cases the compiler-generated ones are sufficient. The
				570	container needs to be a friend of the iterator so that the container's
				571	begin() and end() functions can fill in the iterator's private members
				572	with the appropriate values.
				573
				574	<i>[Chris's Note: I prefer to not make my iterators friends. Instead, two
				575	ctor's are provided for the iterator class: one to start at the end of the
				576	container, and one at the beginning. Typically this is done by providing
				577	two constructors with different signatures.]</i>
				578
				579	There are normally only three member functions that need nontrivial
				580	implementations; the rest are just boilerplate.
				581
Chris Lattner	f7235cd	2003-04-23 16:25:38 +0000	[diff] [blame]	582	const container::value_type&
Chris Lattner	d80c43c	2001-07-09 03:27:08 +0000	[diff] [blame]	583	container::const_iterator::operator*() const {
				584	// find the element and return a reference to it
				585	}
				586
				587	const container::value_type*
				588	container::const_iterator::operator->() const {
Chris Lattner	f7235cd	2003-04-23 16:25:38 +0000	[diff] [blame]	589	return &**this;
Chris Lattner	d80c43c	2001-07-09 03:27:08 +0000	[diff] [blame]	590	}
				591
				592	If there's an underlying real container, operator*() can just return a
				593	reference to the appropriate element. If there's no actual container
				594	and the elements need to be generated on the fly -- what I think of as
				595	a "virtual container" -- things get a bit more complicated; you'll
				596	probably need to give the iterator a value_type member object, and
				597	fill it in when you need to. This might be done as part of the
				598	increment operator (below), or if the operation is nontrivial, you
				599	might choose the "lazy" approach and only generate the actual value
				600	when one of the dereferencing operators is called.
				601
				602	The operator->() function is just boilerplate around a call to
				603	operator*().
				604
Chris Lattner	f7235cd	2003-04-23 16:25:38 +0000	[diff] [blame]	605	container::const_iterator&
Chris Lattner	d80c43c	2001-07-09 03:27:08 +0000	[diff] [blame]	606	container::const_iterator::operator++() {
				607	// the incrementing logic goes here
				608	return *this;
				609	}
				610
				611	container::const_iterator
				612	container::const_iterator::operator++(int) {
				613	const_iterator old(*this);
				614	++*this;
				615	return old;
				616	}
				617
				618	Again, the incrementing logic will usually be trivial if there's a
				619	real container involved, more complicated if you're working with a
				620	virtual container. In particular, watch out for what happens when you
				621	increment past the last valid item -- this needs to produce an
				622	iterator that will compare equal to container.end(), and making this
				623	work is often nontrivial for virtual containers.
				624
				625	The post-increment function is just boilerplate again (and
				626	incidentally makes it obvious why all the experts recommend using
				627	pre-increment wherever possible).
				628
				629	bool operator==(container::const_iterator lhs,
				630	container::const_iterator rhs) {
				631	// equality comparison goes here
				632	}
				633
				634	bool operator!=(container::const_iterator lhs,
				635	container::const_iterator rhs) {
				636	return !(lhs == rhs);
				637	}
				638
				639	For a real container, the equality comparison will usually just
				640	compare the underlying iterators (or pointers or indices or whatever).
				641	The semantics of comparisons for virtual container iterators are often
				642	tricky. Remember that iterator comparison only needs to be defined for
				643	iterators into the same container, so you can often simplify things by
				644	taking for granted that lhs and rhs both point into the same container
				645	object. Again, the second function is just boilerplate.
				646
				647	It's a matter of taste whether iterator arguments are passed by value
				648	or reference; I've shown tham passed by value to reduce clutter, but
				649	if the iterator contains several data members, passing by reference
				650	may be better.
				651
				652	That convers the const-iterator-only situation. When we need separate
				653	const and mutable iterators, one small complication is added beyond
				654	the simple addition of a second class.
				655
				656	class container {
				657	public:
				658	typedef something_or_other value_type;
				659	class const_iterator;
				660	class iterator:
Chris Lattner	2e5cbc2	2003-08-07 21:45:47 +0000	[diff] [blame]	661	public std::iterator<std::forward_iterator_tag, value_type> {
Chris Lattner	d80c43c	2001-07-09 03:27:08 +0000	[diff] [blame]	662	friend class container;
				663	friend class container::const_iterator;
				664	public:
Chris Lattner	f7235cd	2003-04-23 16:25:38 +0000	[diff] [blame]	665	value_type& operator*() const;
Chris Lattner	d80c43c	2001-07-09 03:27:08 +0000	[diff] [blame]	666	value_type* operator->() const;
Chris Lattner	f7235cd	2003-04-23 16:25:38 +0000	[diff] [blame]	667	iterator& operator++();
Chris Lattner	d80c43c	2001-07-09 03:27:08 +0000	[diff] [blame]	668	iterator operator++(int);
				669	friend bool operator==(iterator lhs, iterator rhs);
				670	friend bool operator!=(iterator lhs, iterator rhs);
				671	private:
				672	//...
				673	};
				674	class const_iterator:
Chris Lattner	2e5cbc2	2003-08-07 21:45:47 +0000	[diff] [blame]	675	public std::iterator<std::forward_iterator_tag, value_type> {
Chris Lattner	d80c43c	2001-07-09 03:27:08 +0000	[diff] [blame]	676	friend class container;
				677	public:
				678	const_iterator();
Chris Lattner	f7235cd	2003-04-23 16:25:38 +0000	[diff] [blame]	679	const_iterator(const iterator& i);
				680	const value_type& operator*() const;
Chris Lattner	d80c43c	2001-07-09 03:27:08 +0000	[diff] [blame]	681	const value_type* operator->() const;
Chris Lattner	f7235cd	2003-04-23 16:25:38 +0000	[diff] [blame]	682	const_iterator& operator++();
Chris Lattner	d80c43c	2001-07-09 03:27:08 +0000	[diff] [blame]	683	const_iterator operator++(int);
				684	friend bool operator==(const_iterator lhs,
				685	const_iterator rhs);
				686	friend bool operator!=(const_iterator lhs,
				687	const_iterator rhs);
				688	private:
				689	//...
				690	};
				691	//...
				692	};
				693
				694	There needs to be a conversion from iterator to const_iterator (so
				695	that mixed-type operations, such as comparison between an iterator and
				696	a const_iterator, will work). This is done here by giving
				697	const_iterator a conversion constructor from iterator (equivalently,
				698	we could have given iterator an operator const_iterator()), which
				699	requires const_iterator to be a friend of iterator, so it can copy its
				700	data members. (It also requires the addition of an explicit default
				701	constructor to const_iterator, since the existence of another
				702	user-defined constructor inhibits the compiler-defined one.)
				703
				704	Bidirectional iterators add just two member functions to forward
				705	iterators:
				706
				707	class iterator:
Chris Lattner	2e5cbc2	2003-08-07 21:45:47 +0000	[diff] [blame]	708	public std::iterator<std::bidirectional_iterator_tag, value_type> {
Chris Lattner	d80c43c	2001-07-09 03:27:08 +0000	[diff] [blame]	709	public:
				710	//...
Chris Lattner	f7235cd	2003-04-23 16:25:38 +0000	[diff] [blame]	711	iterator& operator--();
Chris Lattner	d80c43c	2001-07-09 03:27:08 +0000	[diff] [blame]	712	iterator operator--(int);
				713	//...
				714	};
				715
				716	I won't detail the implementations, they're obvious variations on
				717	operator++().
				718
				719	Random access iterators add several more member and friend functions:
				720
				721	class iterator:
Chris Lattner	2e5cbc2	2003-08-07 21:45:47 +0000	[diff] [blame]	722	public std::iterator<std::random_access_iterator_tag, value_type> {
Chris Lattner	d80c43c	2001-07-09 03:27:08 +0000	[diff] [blame]	723	public:
				724	//...
Chris Lattner	f7235cd	2003-04-23 16:25:38 +0000	[diff] [blame]	725	iterator& operator+=(difference_type rhs);
				726	iterator& operator-=(difference_type rhs);
Chris Lattner	d80c43c	2001-07-09 03:27:08 +0000	[diff] [blame]	727	friend iterator operator+(iterator lhs, difference_type rhs);
				728	friend iterator operator+(difference_type lhs, iterator rhs);
				729	friend iterator operator-(iterator lhs, difference_type rhs);
				730	friend difference_type operator-(iterator lhs, iterator rhs);
Chris Lattner	2e5cbc2	2003-08-07 21:45:47 +0000	[diff] [blame]	731	friend bool operator<(iterator lhs, iterator rhs);
				732	friend bool operator>(iterator lhs, iterator rhs);
				733	friend bool operator<=(iterator lhs, iterator rhs);
				734	friend bool operator>=(iterator lhs, iterator rhs);
Chris Lattner	d80c43c	2001-07-09 03:27:08 +0000	[diff] [blame]	735	//...
				736	};
				737
Chris Lattner	f7235cd	2003-04-23 16:25:38 +0000	[diff] [blame]	738	container::iterator&
Chris Lattner	d80c43c	2001-07-09 03:27:08 +0000	[diff] [blame]	739	container::iterator::operator+=(container::difference_type rhs) {
				740	// add rhs to iterator position
				741	return *this;
				742	}
				743
Chris Lattner	f7235cd	2003-04-23 16:25:38 +0000	[diff] [blame]	744	container::iterator&
Chris Lattner	d80c43c	2001-07-09 03:27:08 +0000	[diff] [blame]	745	container::iterator::operator-=(container::difference_type rhs) {
				746	// subtract rhs from iterator position
				747	return *this;
				748	}
				749
				750	container::iterator operator+(container::iterator lhs,
				751	container::difference_type rhs) {
				752	return iterator(lhs) += rhs;
				753	}
				754
				755	container::iterator operator+(container::difference_type lhs,
				756	container::iterator rhs) {
				757	return iterator(rhs) += lhs;
				758	}
				759
				760	container::iterator operator-(container::iterator lhs,
				761	container::difference_type rhs) {
				762	return iterator(lhs) -= rhs;
				763	}
				764
				765	container::difference_type operator-(container::iterator lhs,
				766	container::iterator rhs) {
				767	// calculate distance between iterators
				768	}
				769
Chris Lattner	2e5cbc2	2003-08-07 21:45:47 +0000	[diff] [blame]	770	bool operator<(container::iterator lhs, container::iterator rhs) {
Chris Lattner	d80c43c	2001-07-09 03:27:08 +0000	[diff] [blame]	771	// perform less-than comparison
				772	}
				773
Chris Lattner	2e5cbc2	2003-08-07 21:45:47 +0000	[diff] [blame]	774	bool operator>(container::iterator lhs, container::iterator rhs) {
				775	return rhs < lhs;
Chris Lattner	d80c43c	2001-07-09 03:27:08 +0000	[diff] [blame]	776	}
				777
Chris Lattner	2e5cbc2	2003-08-07 21:45:47 +0000	[diff] [blame]	778	bool operator<=(container::iterator lhs, container::iterator rhs) {
				779	return !(rhs < lhs);
Chris Lattner	d80c43c	2001-07-09 03:27:08 +0000	[diff] [blame]	780	}
				781
Chris Lattner	2e5cbc2	2003-08-07 21:45:47 +0000	[diff] [blame]	782	bool operator>=(container::iterator lhs, container::iterator rhs) {
				783	return !(lhs < rhs);
Chris Lattner	d80c43c	2001-07-09 03:27:08 +0000	[diff] [blame]	784	}
				785
				786	Four of the functions (operator+=(), operator-=(), the second
Chris Lattner	2e5cbc2	2003-08-07 21:45:47 +0000	[diff] [blame]	787	operator-(), and operator<()) are nontrivial; the rest are
Chris Lattner	d80c43c	2001-07-09 03:27:08 +0000	[diff] [blame]	788	boilerplate.
				789
				790	One feature of the above code that some experts may disapprove of is
				791	the declaration of all the free functions as friends, when in fact
				792	only a few of them need direct access to the iterator's private data.
				793	I originally got into the habit of doing this simply to keep the
				794	declarations together; declaring some functions inside the class and
				795	some outside seemed awkward. Since then, though, I've been told that
				796	there's a subtle difference in the way name lookup works for functions
				797	declared inside a class (as friends) and outside, so keeping them
				798	together in the class is probably a good idea for practical as well as
				799	aesthetic reasons.
				800
				801	I hope all this is some help to anyone who needs to write their own
				802	STL-like containers and iterators.
				803
				804	--
Chris Lattner	2e5cbc2	2003-08-07 21:45:47 +0000	[diff] [blame]	805	Ross Smith <ross.s@ihug.co.nz> The Internet Group, Auckland, New Zealand
Chris Lattner	d80c43c	2001-07-09 03:27:08 +0000	[diff] [blame]	806	</pre>
				807
				808
				809	<!-- *********************************************************************** -->
				810	</ul><table width="100%" bgcolor="#330077" border=0 cellpadding=4 cellspacing=0><tr><td align=center><font color="#EEEEFF" size=+2 face="Georgia,Palatino"><b>
				811	<a name="seealso">See Also
				812	</b></font></td></tr></table><ul>
				813	<!-- *********************************************************************** -->
				814
Misha Brukman	1b36d67	2003-10-06 19:26:00 +0000	[diff] [blame]	815	A lot of these comments and recommendations have been culled for other sources.
				816	Two particularly important books for our work are:<p>
Chris Lattner	d80c43c	2001-07-09 03:27:08 +0000	[diff] [blame]	817
				818	<ol>
				819	<li><a href="http://www.aw.com/product/0,2627,0201924889,00.html">Effective C++</a> by Scott Meyers. There is an online version of the book (only some chapters though) <a href="http://www.awlonline.com/cseng/meyerscddemo/">available as well</a>.
				820	<li><a href="http://cseng.aw.com/book/0,3828,0201633620,00.html">Large-Scale C++ Software Design</a> by John Lakos
				821	</ol><p>
				822
Misha Brukman	1b36d67	2003-10-06 19:26:00 +0000	[diff] [blame]	823	If you get some free time, and you haven't read them: do so, you might learn
				824	something. :)
Chris Lattner	d80c43c	2001-07-09 03:27:08 +0000	[diff] [blame]	825
				826
				827	<!-- *********************************************************************** -->
				828	</ul>
				829	<!-- *********************************************************************** -->
				830
				831	<hr>
				832	<font size=-1>
				833	<address><a href="mailto:sabre@nondot.org">Chris Lattner</a></address>
				834	<!-- Created: Tue Jan 23 15:19:28 CST 2001 -->
				835	<!-- hhmts start -->
Chris Lattner	c49fcd1	2003-10-13 14:58:11 +0000	[diff] [blame]	836	Last modified: Sun Oct 12 22:12:43 CDT 2003
Chris Lattner	d80c43c	2001-07-09 03:27:08 +0000	[diff] [blame]	837	<!-- hhmts end -->
				838	</font>
				839	</body></html>