made the pack completely portable and wrote relevent bat files to go with it
This commit is contained in:
701
gitportable/usr/share/vim/vim91/doc/develop.txt
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701
gitportable/usr/share/vim/vim91/doc/develop.txt
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@@ -0,0 +1,701 @@
|
||||
*develop.txt* For Vim version 9.1. Last change: 2024 Dec 25
|
||||
|
||||
|
||||
VIM REFERENCE MANUAL by Bram Moolenaar
|
||||
|
||||
|
||||
Development of Vim. *development*
|
||||
|
||||
This text is important for those who want to be involved in further developing
|
||||
Vim.
|
||||
|
||||
1. Design goals |design-goals|
|
||||
2. Coding style |coding-style|
|
||||
3. Design decisions |design-decisions|
|
||||
4. Assumptions |design-assumptions|
|
||||
|
||||
See the file README.txt in the "src" directory for an overview of the source
|
||||
code.
|
||||
|
||||
Vim is open source software. Everybody is encouraged to contribute to help
|
||||
improving Vim. For sending patches a unified diff "diff -u" is preferred.
|
||||
You can create a pull request on github, but it's not required.
|
||||
Also see http://vim.wikia.com/wiki/How_to_make_and_submit_a_patch.
|
||||
|
||||
==============================================================================
|
||||
1. Design goals *design-goals*
|
||||
|
||||
Most important things come first (roughly).
|
||||
|
||||
Note that quite a few items are contradicting. This is intentional. A
|
||||
balance must be found between them.
|
||||
|
||||
|
||||
VIM IS... VI COMPATIBLE *design-compatible*
|
||||
|
||||
First of all, it should be possible to use Vim as a drop-in replacement for
|
||||
Vi. When the user wants to, Vim can be used in compatible mode and hardly
|
||||
any differences with the original Vi will be noticed.
|
||||
|
||||
Exceptions:
|
||||
- We don't reproduce obvious Vi bugs in Vim.
|
||||
- There are different versions of Vi. I am using Version 3.7 (6/7/85) as a
|
||||
reference. But support for other versions is also included when possible.
|
||||
The Vi part of POSIX is not considered a definitive source.
|
||||
- Vim adds new commands, you cannot rely on some command to fail because it
|
||||
didn't exist in Vi.
|
||||
- Vim will have a lot of features that Vi doesn't have. Going back from Vim
|
||||
to Vi will be a problem, this cannot be avoided.
|
||||
- Some things are hardly ever used (open mode, sending an e-mail when
|
||||
crashing, etc.). Those will only be included when someone has a good reason
|
||||
why it should be included and it's not too much work.
|
||||
- For some items it is debatable whether Vi compatibility should be
|
||||
maintained. There will be an option flag for these.
|
||||
|
||||
|
||||
VIM IS... IMPROVED *design-improved*
|
||||
|
||||
The IMproved bits of Vim should make it a better Vi, without becoming a
|
||||
completely different editor. Extensions are done with a "Vi spirit".
|
||||
- Use the keyboard as much as feasible. The mouse requires a third hand,
|
||||
which we don't have. Many terminals don't have a mouse.
|
||||
- When the mouse is used anyway, avoid the need to switch back to the
|
||||
keyboard. Avoid mixing mouse and keyboard handling.
|
||||
- Add commands and options in a consistent way. Otherwise people will have a
|
||||
hard time finding and remembering them. Keep in mind that more commands and
|
||||
options will be added later.
|
||||
- A feature that people do not know about is a useless feature. Don't add
|
||||
obscure features, or at least add hints in documentation that they exist.
|
||||
- Minimize using CTRL and other modifiers, they are more difficult to type.
|
||||
- There are many first-time and inexperienced Vim users. Make it easy for
|
||||
them to start using Vim and learn more over time.
|
||||
- There is no limit to the features that can be added. Selecting new features
|
||||
is one based on (1) what users ask for, (2) how much effort it takes to
|
||||
implement and (3) someone actually implementing it.
|
||||
|
||||
|
||||
VIM IS... MULTI PLATFORM *design-multi-platform*
|
||||
|
||||
Vim tries to help as many users on as many platforms as possible.
|
||||
- Support many kinds of terminals. The minimal demands are cursor positioning
|
||||
and clear-screen. Commands should only use key strokes that most keyboards
|
||||
have. Support all the keys on the keyboard for mapping.
|
||||
- Support many platforms. A condition is that there is someone willing to do
|
||||
Vim development on that platform, and it doesn't mean messing up the code.
|
||||
- Support many compilers and libraries. Not everybody is able or allowed to
|
||||
install another compiler or GUI library.
|
||||
- People switch from one platform to another, and from GUI to terminal
|
||||
version. Features should be present in all versions, or at least in as many
|
||||
as possible with a reasonable effort. Try to avoid that users must switch
|
||||
between platforms to accomplish their work efficiently.
|
||||
- That a feature is not possible on some platforms, or only possible on one
|
||||
platform, does not mean it cannot be implemented. [This intentionally
|
||||
contradicts the previous item, these two must be balanced.]
|
||||
|
||||
|
||||
VIM IS... WELL DOCUMENTED *design-documented*
|
||||
|
||||
- A feature that isn't documented is a useless feature. A patch for a new
|
||||
feature must include the documentation.
|
||||
- Documentation should be comprehensive and understandable. Using examples is
|
||||
recommended.
|
||||
- Don't make the text unnecessarily long. Less documentation means that an
|
||||
item is easier to find.
|
||||
|
||||
|
||||
VIM IS... HIGH SPEED AND SMALL IN SIZE *design-speed-size*
|
||||
|
||||
Using Vim must not be a big attack on system resources. Keep it small and
|
||||
fast.
|
||||
- Computers are becoming faster and bigger each year. Vim can grow too, but
|
||||
no faster than computers are growing. Keep Vim usable on older systems.
|
||||
- Many users start Vim from a shell very often. Startup time must be short.
|
||||
- Commands must work efficiently. The time they consume must be as small as
|
||||
possible. Useful commands may take longer.
|
||||
- Don't forget that some people use Vim over a slow connection. Minimize the
|
||||
communication overhead.
|
||||
- Items that add considerably to the size and are not used by many people
|
||||
should be a feature that can be disabled.
|
||||
- Vim is a component among other components. Don't turn it into a massive
|
||||
application, but have it work well together with other programs.
|
||||
|
||||
|
||||
VIM IS... MAINTAINABLE *design-maintain*
|
||||
|
||||
- The source code should not become a mess. It should be reliable code.
|
||||
- Use the same layout in all files to make it easy to read |coding-style|.
|
||||
- Use comments in a useful way! Quoting the function name and argument names
|
||||
is NOT useful. Do explain what they are for.
|
||||
- Porting to another platform should be made easy, without having to change
|
||||
too much platform-independent code.
|
||||
- Use the object-oriented spirit: Put data and code together. Minimize the
|
||||
knowledge spread to other parts of the code.
|
||||
|
||||
|
||||
VIM IS... FLEXIBLE *design-flexible*
|
||||
|
||||
Vim should make it easy for users to work in their preferred styles rather
|
||||
than coercing its users into particular patterns of work. This can be for
|
||||
items with a large impact (e.g., the 'compatible' option) or for details. The
|
||||
defaults are carefully chosen such that most users will enjoy using Vim as it
|
||||
is. Commands and options can be used to adjust Vim to the desire of the user
|
||||
and its environment.
|
||||
|
||||
|
||||
VIM IS... NOT *design-not*
|
||||
|
||||
- Vim is not a shell or an Operating System. It does provide a terminal
|
||||
window, in which you can run a shell or debugger. E.g. to be able to do
|
||||
this over an ssh connection. But if you don't need a text editor with that
|
||||
it is out of scope (use something like screen or tmux instead).
|
||||
A satirical way to say this: "Unlike Emacs, Vim does not attempt to include
|
||||
everything but the kitchen sink, but some people say that you can clean one
|
||||
with it. ;-)"
|
||||
To use Vim with gdb see |terminal-debugger|. Other (older) tools can be
|
||||
found at http://www.agide.org (link seems dead) and http://clewn.sf.net.
|
||||
- Vim is not a fancy GUI editor that tries to look nice at the cost of
|
||||
being less consistent over all platforms. But functional GUI features are
|
||||
welcomed.
|
||||
|
||||
|
||||
==============================================================================
|
||||
2. Coding style *coding-style*
|
||||
|
||||
These are the rules to use when making changes to the Vim source code. Please
|
||||
stick to these rules, to keep the sources readable and maintainable.
|
||||
|
||||
This list is not complete. Look in the source code for more examples.
|
||||
|
||||
The code repository contains an editorconfig file, that can be used together
|
||||
with the distributed editorconfig plugin |editorconfig-install| to ensure the
|
||||
recommended style is followed.
|
||||
|
||||
|
||||
MAKING CHANGES *style-changes*
|
||||
|
||||
The basic steps to make changes to the code:
|
||||
1. Get the code from github. That makes it easier to keep your changed
|
||||
version in sync with the main code base (it may be a while before your
|
||||
changes will be included).
|
||||
2. Adjust the documentation. Doing this first gives you an impression of how
|
||||
your changes affect the user.
|
||||
3. Make the source code changes.
|
||||
4. Check ../doc/todo.txt if the change affects any listed item.
|
||||
5. Add a test to src/testdir to verify the new behaviour and ensure it won't
|
||||
regress in the future.
|
||||
6. Make a patch with "git diff".
|
||||
7. Make a note about what changed, preferably mentioning the problem and the
|
||||
solution. Send an email to the |vim-dev| maillist with an explanation and
|
||||
include the diff.
|
||||
|
||||
For any non-trivial change, please always create a pull request on github,
|
||||
since this triggers the test suite.
|
||||
|
||||
*style-clang-format*
|
||||
sound.c and sign.c can be (semi-) automatically formated using the
|
||||
`clang-format` formatter according to the distributed .clang-format file.
|
||||
Other source files do not yet correspond to the .clang-format file. This may
|
||||
change in the future and they may be reformatted as well.
|
||||
|
||||
|
||||
C COMPILER *style-compiler* *ANSI-C* *C89* *C99*
|
||||
|
||||
The minimal C compiler version supported is C89, also known as ANSI C.
|
||||
Later standards, such as C99, are not widely supported, or at least not 100%
|
||||
supported. Therefore we use only some of the C99 features and explicitly
|
||||
disallow some (this will gradually be adjusted over time).
|
||||
|
||||
Features not to be used ~
|
||||
|
||||
These C99 features are not to be used, because not enough compilers support
|
||||
them:
|
||||
- Variable length arrays (even in C11 this is an optional feature).
|
||||
- C99 _Bool and _Complex types.
|
||||
- "inline" (it's hardly ever needed, let the optimizer do its work)
|
||||
- flexible array members: Not supported by HP-UX C compiler (John Marriott)
|
||||
|
||||
|
||||
COMMENTS *style-comments*
|
||||
|
||||
Try to avoid putting multiline comments inside a function body: if the
|
||||
function is so complex that you need to separately comment parts of it, you
|
||||
should probably rethink the structure of the function.
|
||||
|
||||
For file headers and function descriptions use: >
|
||||
/*
|
||||
* Description
|
||||
*/
|
||||
<
|
||||
For everything else use: >
|
||||
// comment
|
||||
<
|
||||
|
||||
|
||||
INDENTATION *style-indentation*
|
||||
|
||||
We use 4 space to indent the code. If you are using Vim to edit the source,
|
||||
you don't need to do anything due to the |modeline|.
|
||||
|
||||
For other editors an `.editorconfig` is provided at the root of the repo.
|
||||
|
||||
|
||||
DECLARATIONS *style-declarations*
|
||||
|
||||
Declare, when possible, `for` loop variables in the guard:
|
||||
OK: >
|
||||
for (int i = 0; i < len; ++i)
|
||||
<
|
||||
Wrong: >
|
||||
int i;
|
||||
for (i = 0; i < len; ++i)
|
||||
<
|
||||
Always declare a variable with a default value:
|
||||
OK: >
|
||||
int n = 0;
|
||||
int *ptr = NULL;
|
||||
<
|
||||
Wrong: >
|
||||
int n;
|
||||
int *ptr;
|
||||
<
|
||||
|
||||
|
||||
BRACES *style-braces*
|
||||
|
||||
All curly braces must be returned onto a new line:
|
||||
OK: >
|
||||
if (cond)
|
||||
{
|
||||
cmd;
|
||||
cmd;
|
||||
}
|
||||
else
|
||||
{
|
||||
cmd;
|
||||
cmd;
|
||||
}
|
||||
<
|
||||
Wrong: >
|
||||
if (cond) {
|
||||
cmd;
|
||||
cmd;
|
||||
} else {
|
||||
cmd;
|
||||
cmd;
|
||||
}
|
||||
<
|
||||
OK: >
|
||||
while (cond)
|
||||
{
|
||||
cmd;
|
||||
}
|
||||
<
|
||||
Wrong: >
|
||||
while (cond) {
|
||||
cmd;
|
||||
}
|
||||
<
|
||||
When a block has one line, including comments, the braces can be left out.
|
||||
OK: >
|
||||
if (cond)
|
||||
cmd;
|
||||
else
|
||||
cmd;
|
||||
<
|
||||
Wrong: >
|
||||
if (cond)
|
||||
/*
|
||||
* comment
|
||||
*/
|
||||
cmd;
|
||||
else
|
||||
cmd;
|
||||
<
|
||||
When an `if`/`else` has braces on one block, the other should have it too.
|
||||
OK: >
|
||||
if (cond)
|
||||
{
|
||||
cmd;
|
||||
}
|
||||
else
|
||||
{
|
||||
cmd;
|
||||
cmd;
|
||||
}
|
||||
<
|
||||
Wrong: >
|
||||
if (cond)
|
||||
cmd;
|
||||
else
|
||||
{
|
||||
cmd;
|
||||
cmd;
|
||||
}
|
||||
|
||||
if (cond)
|
||||
{
|
||||
cmd;
|
||||
cmd;
|
||||
}
|
||||
else
|
||||
cmd;
|
||||
<
|
||||
OK: >
|
||||
while (cond)
|
||||
cmd;
|
||||
<
|
||||
Wrong:
|
||||
>
|
||||
while (cond)
|
||||
if (cond)
|
||||
cmd;
|
||||
<
|
||||
|
||||
|
||||
TYPES *style-types*
|
||||
|
||||
Use descriptive types. You can find a list of them in the src/structs.h file
|
||||
and probably in a typedef in the file you are working on.
|
||||
|
||||
Note that all custom types are postfixed with "_T"
|
||||
|
||||
OK: >
|
||||
int is_valid_line_number(linenr_T lnum);
|
||||
<
|
||||
Wrong: >
|
||||
int is_valid_line_number(unsigned long lnum);
|
||||
<
|
||||
|
||||
|
||||
SPACES AND PUNCTUATION *style-spaces*
|
||||
|
||||
No space between a function name and the bracket:
|
||||
|
||||
OK: func(arg);
|
||||
Wrong: func (arg);
|
||||
|
||||
Do use a space after `if`, `while`, `switch`, etc.
|
||||
|
||||
OK: if (arg) for (;;)
|
||||
Wrong: if(arg) for(;;)
|
||||
|
||||
Use a space after a comma or semicolon:
|
||||
|
||||
OK: func(arg1, arg2); for (i = 0; i < 2; ++i)
|
||||
Wrong: func(arg1,arg2); for (i = 0;i < 2;++i)
|
||||
|
||||
Use a space before and after '=', '+', '/', etc.
|
||||
|
||||
Wrong: var=a*5;
|
||||
OK: var = a * 5;
|
||||
|
||||
Use empty lines to group similar actions together.
|
||||
|
||||
OK: >
|
||||
msg_puts_title(_("\n--- Signs ---"));
|
||||
msg_putchar('\n');
|
||||
|
||||
if (rbuf == NULL)
|
||||
buf = firstbuf;
|
||||
else
|
||||
buf = rbuf;
|
||||
|
||||
while (buf != NULL && !got_int)
|
||||
<
|
||||
Wrong: >
|
||||
msg_puts_title(_("\n--- Signs ---"));
|
||||
msg_putchar('\n');
|
||||
if (rbuf == NULL)
|
||||
buf = firstbuf;
|
||||
else
|
||||
buf = rbuf;
|
||||
while (buf != NULL && !got_int)
|
||||
<
|
||||
|
||||
|
||||
FUNCTIONS *style-functions*
|
||||
|
||||
Use function declarations with the return type on a separate indented line.
|
||||
|
||||
OK: >
|
||||
int
|
||||
function_name(int arg1, int arg2)
|
||||
{
|
||||
}
|
||||
<
|
||||
Wrong: >
|
||||
int function_name(int arg1, int arg2)
|
||||
{
|
||||
}
|
||||
<
|
||||
|
||||
Give meaningful names to function parameters.
|
||||
|
||||
|
||||
USE OF COMMON FUNCTIONS *style-common-functions*
|
||||
|
||||
Some functions that are common to use, have a special Vim version. Always
|
||||
consider using the Vim version, because they were introduced with a reason.
|
||||
|
||||
NORMAL NAME VIM NAME DIFFERENCE OF VIM VERSION
|
||||
free() vim_free() Checks for freeing NULL
|
||||
malloc() alloc() Checks for out of memory situation
|
||||
malloc() lalloc() Like alloc(), but has long argument
|
||||
strcpy() STRCPY() Includes cast to (char *), for char_u * args
|
||||
strchr() vim_strchr() Accepts special characters
|
||||
strrchr() vim_strrchr() Accepts special characters
|
||||
isspace() vim_isspace() Can handle characters > 128
|
||||
iswhite() vim_iswhite() Only TRUE for tab and space
|
||||
memcpy() mch_memmove() Handles overlapped copies
|
||||
bcopy() mch_memmove() Handles overlapped copies
|
||||
memset() vim_memset() Uniform for all systems
|
||||
|
||||
|
||||
NAMES *style-names*
|
||||
|
||||
Function names can not be more than 31 characters long (because of VMS).
|
||||
|
||||
Don't use "delete" or "this" as a variable name, C++ doesn't like it.
|
||||
|
||||
Because of the requirement that Vim runs on as many systems as possible, we
|
||||
need to avoid using names that are already defined by the system. This is a
|
||||
list of names that are known to cause trouble. The name is given as a regexp
|
||||
pattern.
|
||||
|
||||
is.*() POSIX, ctype.h
|
||||
to.*() POSIX, ctype.h
|
||||
|
||||
d_.* POSIX, dirent.h
|
||||
l_.* POSIX, fcntl.h
|
||||
gr_.* POSIX, grp.h
|
||||
pw_.* POSIX, pwd.h
|
||||
sa_.* POSIX, signal.h
|
||||
mem.* POSIX, string.h
|
||||
str.* POSIX, string.h
|
||||
wcs.* POSIX, string.h
|
||||
st_.* POSIX, stat.h
|
||||
tms_.* POSIX, times.h
|
||||
tm_.* POSIX, time.h
|
||||
c_.* POSIX, termios.h
|
||||
MAX.* POSIX, limits.h
|
||||
__.* POSIX, system
|
||||
_[A-Z].* POSIX, system
|
||||
E[A-Z0-9]* POSIX, errno.h
|
||||
|
||||
.*_t POSIX, for typedefs. Use .*_T instead.
|
||||
|
||||
wait don't use as argument to a function, conflicts with types.h
|
||||
index shadows global declaration
|
||||
time shadows global declaration
|
||||
new C++ reserved keyword
|
||||
|
||||
clear Mac curses.h
|
||||
echo Mac curses.h
|
||||
instr Mac curses.h
|
||||
meta Mac curses.h
|
||||
newwin Mac curses.h
|
||||
nl Mac curses.h
|
||||
overwrite Mac curses.h
|
||||
refresh Mac curses.h
|
||||
scroll Mac curses.h
|
||||
typeahead Mac curses.h
|
||||
|
||||
basename() GNU string function
|
||||
dirname() GNU string function
|
||||
get_env_value() Linux system function
|
||||
|
||||
|
||||
VARIOUS *style-various*
|
||||
|
||||
Define'd names should be uppercase: >
|
||||
#define SOME_THING
|
||||
<
|
||||
|
||||
Features always start with "FEAT_": >
|
||||
#define FEAT_FOO
|
||||
<
|
||||
|
||||
Don't use '\"', some compilers can't handle it. '"' works fine.
|
||||
|
||||
Don't use: >
|
||||
#if HAVE_SOME
|
||||
<
|
||||
Some compilers can't handle that and complain that "HAVE_SOME" is not defined.
|
||||
Use >
|
||||
#ifdef HAVE_SOME
|
||||
<
|
||||
or >
|
||||
#if defined(HAVE_SOME)
|
||||
<
|
||||
|
||||
STYLE *style-examples*
|
||||
|
||||
One statement per line.
|
||||
|
||||
Wrong: if (cond) a = 1;
|
||||
|
||||
OK: if (cond)
|
||||
a = 1;
|
||||
|
||||
Wrong: while (cond);
|
||||
|
||||
OK: while (cond)
|
||||
;
|
||||
|
||||
Wrong: do a = 1; while (cond);
|
||||
|
||||
OK: do
|
||||
a = 1;
|
||||
while (cond);
|
||||
|
||||
|
||||
==============================================================================
|
||||
3. Design decisions *design-decisions*
|
||||
|
||||
Folding
|
||||
|
||||
Several forms of folding should be possible for the same buffer. For example,
|
||||
have one window that shows the text with function bodies folded, another
|
||||
window that shows a function body.
|
||||
|
||||
Folding is a way to display the text. It should not change the text itself.
|
||||
Therefore the folding has been implemented as a filter between the text stored
|
||||
in a buffer (buffer lines) and the text displayed in a window (logical lines).
|
||||
|
||||
|
||||
Naming the window
|
||||
|
||||
The word "window" is commonly used for several things: A window on the screen,
|
||||
the xterm window, a window inside Vim to view a buffer.
|
||||
To avoid confusion, other items that are sometimes called window have been
|
||||
given another name. Here is an overview of the related items:
|
||||
|
||||
screen The whole display. For the GUI it's something like 1024x768
|
||||
pixels. The Vim shell can use the whole screen or part of it.
|
||||
shell The Vim application. This can cover the whole screen (e.g.,
|
||||
when running in a console) or part of it (xterm or GUI).
|
||||
window View on a buffer. There can be several windows in Vim,
|
||||
together with the command line, menubar, toolbar, etc. they
|
||||
fit in the shell.
|
||||
|
||||
|
||||
Spell checking *develop-spell*
|
||||
|
||||
When spell checking was going to be added to Vim a survey was done over the
|
||||
available spell checking libraries and programs. Unfortunately, the result
|
||||
was that none of them provided sufficient capabilities to be used as the spell
|
||||
checking engine in Vim, for various reasons:
|
||||
|
||||
- Missing support for multibyte encodings. At least UTF-8 must be supported,
|
||||
so that more than one language can be used in the same file.
|
||||
Doing on-the-fly conversion is not always possible (would require iconv
|
||||
support).
|
||||
- For the programs and libraries: Using them as-is would require installing
|
||||
them separately from Vim. That's mostly not impossible, but a drawback.
|
||||
- Performance: A few tests showed that it's possible to check spelling on the
|
||||
fly (while redrawing), just like syntax highlighting. But the mechanisms
|
||||
used by other code are much slower. Myspell uses a hashtable, for example.
|
||||
The affix compression that most spell checkers use makes it slower too.
|
||||
- For using an external program like aspell a communication mechanism would
|
||||
have to be setup. That's complicated to do in a portable way (Unix-only
|
||||
would be relatively simple, but that's not good enough). And performance
|
||||
will become a problem (lots of process switching involved).
|
||||
- Missing support for words with non-word characters, such as "Etten-Leur" and
|
||||
"et al.", would require marking the pieces of them OK, lowering the
|
||||
reliability.
|
||||
- Missing support for regions or dialects. Makes it difficult to accept
|
||||
all English words and highlight non-Canadian words differently.
|
||||
- Missing support for rare words. Many words are correct but hardly ever used
|
||||
and could be a misspelled often-used word.
|
||||
- For making suggestions the speed is less important and requiring to install
|
||||
another program or library would be acceptable. But the word lists probably
|
||||
differ, the suggestions may be wrong words.
|
||||
|
||||
|
||||
Spelling suggestions *develop-spell-suggestions*
|
||||
|
||||
For making suggestions there are two basic mechanisms:
|
||||
1. Try changing the bad word a little bit and check for a match with a good
|
||||
word. Or go through the list of good words, change them a little bit and
|
||||
check for a match with the bad word. The changes are deleting a character,
|
||||
inserting a character, swapping two characters, etc.
|
||||
2. Perform soundfolding on both the bad word and the good words and then find
|
||||
matches, possibly with a few changes like with the first mechanism.
|
||||
|
||||
The first is good for finding typing mistakes. After experimenting with
|
||||
hashtables and looking at solutions from other spell checkers the conclusion
|
||||
was that a trie (a kind of tree structure) is ideal for this. Both for
|
||||
reducing memory use and being able to try sensible changes. For example, when
|
||||
inserting a character only characters that lead to good words need to be
|
||||
tried. Other mechanisms (with hashtables) need to try all possible letters at
|
||||
every position in the word. Also, a hashtable has the requirement that word
|
||||
boundaries are identified separately, while a trie does not require this.
|
||||
That makes the mechanism a lot simpler.
|
||||
|
||||
Soundfolding is useful when someone knows how the words sounds but doesn't
|
||||
know how it is spelled. For example, the word "dictionary" might be written
|
||||
as "daktonerie". The number of changes that the first method would need to
|
||||
try is very big, it's hard to find the good word that way. After soundfolding
|
||||
the words become "tktnr" and "tkxnry", these differ by only two letters.
|
||||
|
||||
To find words by their soundfolded equivalent (soundalike word) we need a list
|
||||
of all soundfolded words. A few experiments have been done to find out what
|
||||
the best method is. Alternatives:
|
||||
1. Do the sound folding on the fly when looking for suggestions. This means
|
||||
walking through the trie of good words, soundfolding each word and
|
||||
checking how different it is from the bad word. This is very efficient for
|
||||
memory use, but takes a long time. On a fast PC it takes a couple of
|
||||
seconds for English, which can be acceptable for interactive use. But for
|
||||
some languages it takes more than ten seconds (e.g., German, Catalan),
|
||||
which is unacceptably slow. For batch processing (automatic corrections)
|
||||
it's too slow for all languages.
|
||||
2. Use a trie for the soundfolded words, so that searching can be done just
|
||||
like how it works without soundfolding. This requires remembering a list
|
||||
of good words for each soundfolded word. This makes finding matches very
|
||||
fast but requires quite a lot of memory, in the order of 1 to 10 Mbyte.
|
||||
For some languages more than the original word list.
|
||||
3. Like the second alternative, but reduce the amount of memory by using affix
|
||||
compression and store only the soundfolded basic word. This is what Aspell
|
||||
does. Disadvantage is that affixes need to be stripped from the bad word
|
||||
before soundfolding it, which means that mistakes at the start and/or end
|
||||
of the word will cause the mechanism to fail. Also, this becomes slow when
|
||||
the bad word is quite different from the good word.
|
||||
|
||||
The choice made is to use the second mechanism and use a separate file. This
|
||||
way a user with sufficient memory can get very good suggestions while a user
|
||||
who is short of memory or just wants the spell checking and no suggestions
|
||||
doesn't use so much memory.
|
||||
|
||||
|
||||
Word frequency
|
||||
|
||||
For sorting suggestions it helps to know which words are common. In theory we
|
||||
could store a word frequency with the word in the dictionary. However, this
|
||||
requires storing a count per word. That degrades word tree compression a lot.
|
||||
And maintaining the word frequency for all languages will be a heavy task.
|
||||
Also, it would be nice to prefer words that are already in the text. This way
|
||||
the words that appear in the specific text are preferred for suggestions.
|
||||
|
||||
What has been implemented is to count words that have been seen during
|
||||
displaying. A hashtable is used to quickly find the word count. The count is
|
||||
initialized from words listed in COMMON items in the affix file, so that it
|
||||
also works when starting a new file.
|
||||
|
||||
This isn't ideal, because the longer Vim is running the higher the counts
|
||||
become. But in practice it is a noticeable improvement over not using the word
|
||||
count.
|
||||
|
||||
==============================================================================
|
||||
4. Assumptions *design-assumptions*
|
||||
|
||||
Size of variables:
|
||||
char 8 bit signed
|
||||
char_u 8 bit unsigned
|
||||
int 32 or 64 bit signed (16 might be possible with limited features)
|
||||
unsigned 32 or 64 bit unsigned (16 as with ints)
|
||||
long 32 or 64 bit signed, can hold a pointer
|
||||
|
||||
Note that some compilers cannot handle long lines or strings. The C89
|
||||
standard specifies a limit of 509 characters.
|
||||
|
||||
vim:tw=78:ts=8:noet:ft=help:norl:
|
||||
Reference in New Issue
Block a user