UltiSnips/doc/UltiSnips.txt

*UltiSnips.txt*  The Ultimate Plugin for snippets in Vim.

UltiSnips                                      *snippet* *snippets* *UltiSnips*

1. Description                                  |UltiSnips-description|
2. Installation and Updating                    |UltiSnips-installnupgrade|
   2.1 Installation                             |UltiSnips-installation|
   2.2 Deinstallation                           |UltiSnips-deinstallation|
   2.3 Updating                                 |UltiSnips-updating|
3. Settings & Commands                          |UltiSnips-settings|
   3.1 Commands                                 |UltiSnips-commands|
   3.2 Triggers                                 |UltiSnips-triggers|
   3.3 Snippet Search Path                      |UltiSnips-snippet-search-path|
   3.4 Warning About Select Mode Mappings       |UltiSnips-warning-smappings|
   3.5 Functions                                |UltiSnips-functions|
      3.5.1 UltiSnips_AddSnippet                |UltiSnips_AddSnippet|
      3.5.2 UltiSnips_Anon                      |UltiSnips_Anon|
4. Syntax                                       |UltiSnips-syntax|
   4.1 Adding Snippets                          |UltiSnips-adding-snippets|
      4.1.1 Character Escaping                  |UltiSnips-character-escaping|
   4.2 Plaintext Snippets                       |UltiSnips-plaintext-snippets|
   4.3 Interpolation                            |UltiSnips-interpolation|
      4.3.1 Shellcode                           |UltiSnips-shellcode|
      4.3.2 VimScript                           |UltiSnips-vimscript|
      4.3.3 Python                              |UltiSnips-python|
      4.3.4 Global Snippets                     |UltiSnips-globals|
   4.4 Tab Stops and Placeholders               |UltiSnips-tabstops|
   4.6 Mirrors                                  |UltiSnips-mirrors|
   4.7 Transformations                          |UltiSnips-transformations|
      4.7.1 Replacement String                  |UltiSnips-replacement-string|
      4.7.2 Demos                               |UltiSnips-demos|
   4.8 Clearing snippets                        |UltiSnips-clearing-snippets|
5. Helping out                                  |UltiSnips-helping|      
6. Contact                                      |UltiSnips-contact|      
7. Contributors                                 |UltiSnips-contributors|
   7.1 Patches & Coding                         |UltiSnips-contricoding|
   7.2 Snippets                                 |UltiSnips-contrisnippets|

For Vim version 7.0 or later.
This plugin only works if 'compatible' is not set.
{Vi does not have any of these features}

This plugin needs Python support >= 2.6 compiled into Vim.

=============================================================================
DESCRIPTION                                           *UltiSnips-description*

UltiSnips aims to provide a snippets solution that users came to expect from
editors. A Snippet is a short piece of text which is either typed very often
or which contains a lot of redundant text. Such snippets are very often
encountered in structured text like Source Code but I also use them for email
signatures and to insert the current date or time into the text while typing.

UltiSnips is an implementation that is developed with in the philosophy of TDD
(Test driven development). This guarantees that features do not disappear and
bugs do not reappear after they have been fixed once.

You can learn what UltiSnips can do by watching some short screencasts and
reading the accompanying blog posts on my blog:

http://www.sirver.net/blog/2011/12/30/first-episode-of-ultisnips-screencast/
http://www.sirver.net/blog/2012/01/08/second-episode-of-ultisnips-screencast/


 Acknowledgments:                                 *UltiSnips-acknowledgments*

UltiSnips is inspired by the snippets solution implemented in TextMate
(http://macromates.com/). The idea of implementing snippets for vim is not new
and I want to thank Michael Sanders (Author of snipMate) for some
implementation details I stole from him and for the permission to use some of
his snippets.

=============================================================================
2. INSTALLATION AND UPDATING                       *UltiSnips-installnupdate*


2.1 Installation                                     *UltiSnips-installation*
----------------

UltiSnips has only been tested on Mac OS X and Linux. Like TextMates Snippets
it also relies heavily on shell integration, therefore Windows users will have
only a part of the functionality.

To use UltiSnips, you need a python enabled Vim 7. You have python if
   :echo has("python")
yields '1'.

If you have Python, you only need to install UltiSnips. The recommended way to
do so is by using bzr (http://bazaar-vcs.org/). It is in all major linux
distribution (either package bzr or bazaar) and can be easily installed under
Mac OS X: >
   $ easy_install bzr

To get UltiSnips, check it out into a directory of your choice. Then add this
directory to your Vim runtime path: >
   $ cd ~/.vim/
   $ bzr get lp:ultisnips ultisnips_rep
   $ vim ~/.vimrc

add the line: >
   set runtimepath+=~/.vim/ultisnips_rep

Restart vim. UltiSnips should work now. To access the help, use >
   :helptags ~/.vim/ultisnips_rep/doc
   :help UltiSnips

2.2 Deinstallation                                 *UltiSnips-deinstallation*
------------------

To Uninstall UltiSnips, remove the directory you installed it to and remove
the path from your vim runtimepath: >
   $ rm -rf ~/.vim/ultisnips_rep
   $ vim ~/.vimrc

remove the line: >
   set runtimepath+=~/.vim/ultisnips_rep

2.3 Updating                                             *UltiSnips-updating*
------------

To Update an installation, simply pull the latest revision: >
   $ cd ~/.vim/ultisnips_rep
   $ bzr pull

=============================================================================
3. SETTINGS                                              *UltiSnips-settings*

3.1 Commands                                             *UltiSnips-commands*
------------

                                                             *:UltiSnipsEdit*
UltiSnipsEdit opens or creates your private snippet definition file for the
current filetype. You can easily open them manually of course, this is just a
shortcut. There is also a variable called: >
   g:UltiSnipsEditSplit
which can be set to "normal" (default), "horizontal" or "vertical" that
defines if a new window should be opened for the edit. There is also a
variable called: >
   g:UltiSnipsSnippetsDir
that, when set to a directory like "~/.vim/mydir/UltiSnips", becomes the base
directory for the snippet file to open. For example, if it is set to
"~/.vim/mydir/UltiSnips" and the current 'filetype' is "cpp", then
:UltiSnipsEdit will open "~/.vim/mydir/UltiSnips/cpp.snippets".

3.2 Triggers                                             *UltiSnips-triggers*
------------

You can freely define the keys used to expand a snippet and jump forward and
backwards in it. There is also a key to list all snippets available for the
current expand situation. The variables with the default values are: >
   g:UltiSnipsExpandTrigger               <tab>
   g:UltiSnipsListSnippets                <c-tab>
   g:UltiSnipsJumpForwardTrigger          <c-j>
   g:UltiSnipsJumpBackwardTrigger         <c-k>

It is possible to set the Expand and Forward trigger to the same value. You
can get a more TextMate like configuration by adding the next three lines to
your vimrc: >
   let g:UltiSnipsExpandTrigger="<tab>"
   let g:UltiSnipsJumpForwardTrigger="<tab>"
   let g:UltiSnipsJumpBackwardTrigger="<s-tab>"

3.3 Snippet Search Path                       *UltiSnips-snippet-search-path*
-----------------------

UltiSnips lets you override the name of the directories that are searched
for snippets. You need to set the variable g:UltiSnipsSnippetDirectories,
which defaults to: >
   g:UltiSnipsSnippetDirectories          ["UltiSnips"] 

Snippet definition files are searched in 'runtimepath', but the 'runtimepath'
variable is traversed in reversed order (last item first). If you would like
to have UltiSnips traverse this in proper order, add these to your vimrc: >
   let g:UltiSnipsDontReverseSearchPath="1"

In each directory, UltiSnips will search for the folder names in the order
they appear in g:UltiSnipsSnippetDirectories. If you keep your snippets in a
folder called "mycoolsnippets" in your .vim directory and you want the
snippets that ship with UltiSnips to be available as well, use >
   let g:UltiSnipsSnippetDirectories=["UltiSnips", "mycoolsnippets"]
If you do not want the shipped snippets to be available, only use
"mycoolsnippets".

By default, UltiSnips will check for updates to .snippets files whenever
it is activated. This behavior can be disabled as follows: >
   let g:UltiSnipsDoHash=0

See |UltiSnips-adding-snippet| for an introduction which files are parsed for
which file type.

3.4 Warning About Select Mode Mappings          *UltiSnips-warning-smappings*
--------------------------------------

The help for vim's *mapmode-s* states: >
   NOTE: Mapping a printable character in Select mode may confuse the user.
   It's better to explicitly use :xmap and :smap for printable characters.  Or
   use :sunmap after defining the mapping.

But most vim plugins (even the ones shipped with vim) do not adhere to this.
As UltiSnips uses select mode to mark tabstops in snippets for overwriting
these wrong mappings get in the way. UltiSnips therefore defaults to
*:sunmap* all mappings for printable characters in select mode. It will not
touch any other mappings, especially not normal, insert or visual mode
mappings.

If this behaviour is not desired, you can disable it via >
   let g:UltiSnipsRemoveSelectModeMappings = 0

If you want to keep certain mappings, you can modify the list of ignores for
this feature. For example >
   let g:UltiSnipsMappingsToIgnore = [ "somePlugin", "otherPlugin" ]

will not unmap any mapping that contains the string "somePlugin" or
"otherPlugin" in its complete definition as listed by *:smap* .


3.5 Functions                                           *UltiSnips-functions*
-------------

UltiSnips provides two functions for extending core functionality.

 3.5.1 UltiSnips_AddSnippet                            *UltiSnips_AddSnippet*

The first function is UltiSnips_AddSnippet(trigger, value, description,
options, ...) which adds a new snippet to the current list of snippets with
the provided trigger, value, description, and options, see |UltiSnips-syntax|
for details on the meaning of those. All of the arguments are strings. You can
also specify the filetype for the new snippet with the final optional
argument.

 3.5.2 UltiSnips_Anon                                        *UltiSnips_Anon*

The second function is UltiSnips_Anon(value, ...), which expands an anonymous
Snippet. The snippet that gets expanded doesn't get added to the global list
of snippets, so it can't be expanded a second time unless the function is
called again. The value argument is the same as |UltiSnips_AddSnippet|. There
are also optional arguments, which are 1) the trigger, 2) the description of
the snippet, and 3) the options. All of the optional arguments are the same as
the |UltiSnips_AddSnippet| function. The description is unused right now,
whereas the trigger and options can change the way the snippet expands.

This feature is frequently used in .vimrc. A typical use case from my
restructured text file looks like this:

   inoremap <silent> $$ $$<C-R>=UltiSnips_Anon(':latex:\`$1\`', '$$')<cr>

This expands the snippet whenever I type two $ signs. Note that In the right
hand site of the mapping, I retype the '$$' trigger and also inform UltiSnips
about the trigger; if I do not do this or give an empty trigger, vim will
trick UltiSnips by unreliably claiming that there is already one or zero '$'
signs before the snippet is expanded.

=============================================================================
4. SYNTAX                                                  *UltiSnips-syntax*

This chapter describes where to add new snippets and how to write them. I'll
provide many examples to make things clearer.

4.1 Adding Snippets                               *UltiSnips-adding-snippets*
-------------------

See |UltiSnips-snippet-search-path| for an explanation of where directories
with snippet definitions are expected.

While iterating over the snippet definition directories found, files are
looked for called ft.snippets or *_ft.snippets where "ft" is the current
'filetype', and the "*" matches anything, for example: >
   ruby.snippets
   c.snippets
   my_c.snippets
   perl.snippets
These files contain the snippet definitions for the various file types. A
special file is >
   all.snippets
which contains snippets that are always expanded, no matter what file type is
defined. For example, I keep mail signatures and date insertion snippets here.

The dotted file type syntax of vim is supported. For example, for my cpp or
CUDA files, I keep the file type set to ":set ft=cpp.c" or ":set
ft=cuda.cpp.c". This activates all snippets for each file type in the order
specified.

As an alternative, a snippet file may contain a line that looks like this: >
   extends ft1, ft2, ft3
For example, the first line in cpp.snippets looks like this: >
   extends c
This means, first check all triggers for c, then add the triggers from this
file. This is a convenient way to add more special cases to more general ones.
Multiple "extends" lines are permitted throughout the snippets file.

The snippets file format is simple. A line starting with # is a comment, each
snippet starts with a line in the form of: >
   snippet tab_trigger [ "description" [ options ] ]
The following lines are the snippets definition; a line starting with >
   endsnippet
marks the end of the snippet. The trailing newline is chopped from the
definition. In the starting line, the description and options are optional.

If you want to use a multi-word trigger, you can surround the trigger with any
single character on each side. e.g. >
    snippet "tab trigger" [ "description" [ options ] ]
or >
    snippet !"tab trigger"! [ "description" [ options ] ]
if you actually want to include the double-quote characters in the trigger.

The description is only needed when more than one snippet is defined with the
same tab trigger. The user is then given a choice and the description is
displayed for the user as helper.

The options is a word of characters, each turning a specific option for this
snippet on. The options currently supported are >
   !   Overwrite - This snippet will overwrite all previously defined
       snippets with this tab trigger. Default is to let the user choose at
       expansion which snippet to expand. This option is useful to overwrite
       bundled tab stops with user defined ones.
   b   Beginning of line - This snippet will only be expanded if you are at
       the beginning of a line (that is if there are only whitespaces in front
       of the cursor). Default is to expand snippets at every position, even
       in the middle of a line. Most of my snippets have this option set, it
       keeps UltiSnips out of the way.
   i   Inword expansion - Normally, triggers need whitespace before them to be
       expanded. With this option, triggers are also expanded in the middle of
       a word.
   w   Word boundary - Normally, triggers need whitespace before them to be
       expanded. With this option, the trigger will be expanded at a "word"
       boundary as well, where word characters are letters, digits, and the
       underscore character ('_').  This enables expansion of a trigger that
       adjoins punctuation (for example) without expanding suffixes of larger
       words.
   r   Regular expression - This uses a python regular expression for the
       match. The regular expression MUST be surrounded like a multi-word
       trigger (see above) even if it doesn't have any spaces. The resulting
       match is also passed to any python code blocks in your snippet
       definition as the local variable "match".
   t   Don't expand tabs - By default, UltiSnips tries to expand leading tabs
       in a snippet to match the results of automatic indentation. If this
       option is set, UltiSnips will not try to do this expansion, and will
       leave the tabs alone. This can be useful for snippets dealing with
       tab delimited formats, etc.
   f   Do not turn 'formatoptions' off when expanding the snippet. Normally,
       UltiSnips will disable the 'c' and the 't' option of 'formatoptions'
       because otherwise, Vim might break a line without UltiSnips noticing
       and this might mess up the snippet completely. This is useful for
       snippets that need paragraphs in their tabstops.
<

 4.1.1 Character Escaping:                             *UltiSnips-character-escaping*

In the snippet descriptions, various characters have special meaning
(e.g. '`{$\). If you want to insert any one of these characters literally,
prepend them with a single backslash (\).

4.2 Plaintext Snippets                         *UltiSnips-plaintext-snippets*
----------------------

Lets start with a simple example. Add this to your all snippets file: >
   ~/.vim/UltiSnips/all.snippets

------------------- SNIP -------------------
snippet bye "My mail signature"
Good bye, Sir. Hope to talk to you soon.
- Arthur, King of Britain
endsnippet
------------------- SNAP -------------------

UltiSnips will pick up that you added/changed this file automatically, so just 
try it in insert mode:
bye<tab> -->
Good bye, Sir. Hope to talk to you soon.
- Arthur, King of Britain

4.3 Interpolation                                   *UltiSnips-interpolation*
-----------------

 4.3.1 Shellcode:                                         *UltiSnips-shellcode*

You can enter shellcode in your snippets in nearly all places. Shell code is
written to a script and then executed. The output is inserted into the snippet
instead of the shell code itself. Since the code is executed as a shell
script, you can use #!/bin/ notation to feed the input of your code to every
program you like. Let's consider an example that inserts the current date.

------------------- SNIP -------------------
snippet today
Today is the `date +%d.%m.%y`.
endsnippet
------------------- SNAP -------------------

today<tab> ->
Today is the 15.07.09.

Another example doing the same using perl
------------------- SNIP -------------------
snippet today
Today is `#!/usr/bin/perl
@a = localtime(); print $a[3] . '.' . $a[4] . '.' . ($a[5]+1900);`.
endsnippet
------------------- SNAP -------------------
today<tab> ->
Today is 15.6.2009.

 4.3.2 VimScript:                                         *UltiSnips-vimscript*

You can also use VimScript (also sometimes called VimL) in interpolation. This
works very much the same as interpolation of shellcode, expect that it must be
started by using `!v `. Let's consider a simple example, that counts the
indent of the current line:

------------------- SNIP -------------------
snippet indent
Indent is: `!v indent(".")`.
endsnippet
------------------- SNAP -------------------
    (note the 4 spaces in front): indent<tab> ->
    (note the 4 spaces in front): Indent is: 4.

 4.3.3 Python:                                               *UltiSnips-python*

By far the most powerful interpolation is by using python code. The syntax is
similar to the one for Vimscript, but in python code the value of the property
"rv" on the "snip" object is inserted at the position of the code. Also, the
code is inside a `!p ` block.  Python code gets some special variables defined
which can be used: >

   fn   - The current filename
   path - The complete path to the current file
   t    - The values of the placeholders, t[1] -> current text of ${1} and so on
   snip - Provides easy indentation handling.

The snip object provides the following methods: >

    snip.mkline(line="", indent=None):
        Returns a line ready to be appended to the result. If indent
        is None, then mkline prepends spaces and/or tabs appropriate to the
        current tabstop and expandtab variables.

    snip.shift(amount=1):
        Shifts the default indentation level used by mkline right by the
        number of spaces defined by shiftwidth, 'amount' times.

    snip.unshift(amount=1):
        Shifts the default indentation level used by mkline left by the
        number of spaces defined by shiftwidth, 'amount' times.

    snip.reset_indent():
        Resets the indentation level to its initial value.

    snip.opt(var, default):
        Checks if the vim variable "var" has been set, if so, it returns it,
        otherwise it returns "default".

The snip object provides some properties as well: >

    snip.rv:
        the text that will fill this python block's position, it always starts
        out as an empty string. This deprecates the "res" variable.

    snip.c:
        the text currently in the python block's position in the snippet
        in it. You can check if snip.c is != "" to make sure that the
        interpolation is only done once. This deprecates the "cur" variable.

    snip.fn:
        the current filename.

    snip.basename:
        the current filename without it's extension.

    snip.ft:
        the current filetype.

The snip object also provides some operators to make python snippets
easier: >

    snip >> amount:
        is equivalent to snip.shift(amount)
    snip << amount:
        is equivalent to snip.unshift(amount)
    snip += line:
        is equivalent to "snip.rv += '\n' + snip.mkline(line)"

Any variables set in a python block can be used in any following blocks.
Also, the vim, re, os, string and random modules are already imported inside
the snippet code. This allows for very flexible snippets. For example, the
following snippet mirrors the first Tab Stops value on the same line in
uppercase and right aligned:

------------------- SNIP -------------------
snippet wow
${1:Text}`!p snip.rv = (75-2*len(t[1]))*' '+t[1].upper()`
endsnippet
------------------- SNAP -------------------
wow<tab>Hello World ->
Hello World                                                     HELLO WORLD

 4.3.4 Global Snippets:                                   *UltiSnips-globals*

Global snippets provide a way to take common code out of snippets. Currently,
only python code is supported. The result of executing the contents of the
snippet is put into the globals of each python block in the snippet file. To
create a global snippet, you use the keyword "global" in place of "snippet",
and for python code, you use "!p" for the trigger, for example, the following
is identical to the previous example, except that "upper_right" can be reused:

------------------- SNIP -------------------
global !p
def upper_right(inp):
    return (75 - 2 * len(inp))*' ' + inp.upper()
endglobal

snippet wow
${1:Text}`!p snip.rv = upper_right(t[1])`
endsnippet
------------------- SNAP -------------------
wow<tab>Hello World ->
Hello World                                                     HELLO WORLD

Sometimes you want to have helper functions that are available in all your
snippet files. This is easily achieved using a global snippet and a python
module. First, add a search path to your python path by adding something along
this line to your vimrc: >

   py import sys; sys.path.append("/home/sirver/.vim/python")

Now use a global snippet in your snippet file to import modules from this
directory: >

   global !p
   from my_snippet_helpers import *
   endglobals

4.4 Tab Stops and Placeholders  *UltiSnips-tabstops* *UltiSnips-placeholders*
------------------------------

Very often, it is convenient to quickly add some text snippet and jump on to
the next point of interest. This is were tabstops come in:

------------------- SNIP -------------------
snippet jump
I $1 I was a $2.
$0
endsnippet
------------------- SNAP -------------------
jump<tab>wish<c-j>hunter<c-j>more text ->
I wish I was a hunter.
more text

You can use <c-j> and <c-k> to jump to the next tab or the previous. <Tab> was
not used for jumping forward because many people (like myself) use <tab> also
for completion. $0 is a special tab: This is the last tab in the snippet, no
matter how many tabs were defined before.

Most of the time it is more useful to have some default text for a tabstop and
sometimes it is also useful to have a tab stop in a tab stop. Consider the
next example which could be a real life scenario from a HTML snippet:

------------------- SNIP -------------------
snippet a
<a href="$1"${2: class="${3:link}"}>
    $0
</a>
endsnippet
------------------- SNAP -------------------

Here, $1 marks the first tabstop; it is assumed that you always want to add a
url as href. After entering it you jump to $2 which has the default text '
class="link"'. Now, you can either hit backspace, because you do not want to
enter a class attribute for this tag or you hit <c-j> to change the class name
(which is tab stop $3). When you are satisfied with the first line you hit
<c-j> again to finish this snippet and continue inside the anchor.

a<tab>http://www.google.com<c-j><BS><c-j>hi ->
<a href="http://www.google.com">
	hi
</a>

a<tab>http://www.google.com<c-j><c-j>visited<c-j>hi ->
<a href="http://www.google.com" class="visited">
	hi
</a>

Default tab stop text can also contain mirrors, transformations or
interpolation.

4.6 Mirrors                                               *UltiSnips-mirrors*
-----------

Mirrors simply repeat the content of a tabstop. A classical example would be a
TeX Environment which needs a \begin{} and an \end{} tag:

------------------- SNIP -------------------
snippet env
\begin{${1:enumerate}}
    $0
\end{$1}
endsnippet
------------------- SNAP -------------------
env<tab>itemize ->
\begin{itemize}

\end{itemize}

Another typical example is #ifndef block in C code:
------------------- SNIP -------------------
snippet ifndef
#ifndef ${1:SOME_DEFINE}
#define $1
$0
#endif /* $1 */
endsnippet
------------------- SNAP -------------------
ifndef<tab>WIN32 ->
#ifndef WIN32
#define WIN32

#endif /* WIN32 */

4.7 Transformations                               *UltiSnips-transformations*
-------------------

A complete description of the features follows, the chapter closes with some
demos, because this feature is rather mighty and hard to understand.

Transformations are like mirrors. But instead of just verbatim copying text
from the original tab stop, a regular expression is matched to the content of
the referenced tab stop and a transformation is then applied to the matched
pattern. UltiSnips follows the syntax and features of TextMate very closely
here.

A Transformation has the syntax >
   ${<tab stop no/regular expression/replacement/options}

with >
   tab stop no        - The number of the tab stop to reference
   regular expression - The regular expression to match to the value of the
                        tab stop
   replacement        - The replacement string, see below
   options            - options for the regular expression

The options can be any combination of >
   g    - global replace, replaces all matches of the regular expression, not
        just the first

Regular expressions are not handled here. Python regular expressions are used
internally, so the reference for matching is the re module of python:
   http://docs.python.org/library/re.html

The replacement string is using a own syntax and is handled in the next paragraph.

 4.7.1 Replacement String:                       *UltiSnips-replacement-string*

The replacement string can contain $no variables to reference matched groups
in the regular expression, $0 is special and yields the whole match. The
replacement string can also contain special escape sequences: >
   \u   - Uppercase next letter;
   \l   - Lowercase next letter
   \U   - Uppercase everything till the next \E
   \L   - Lowercase everything till the next \E
   \E   - End upper or lowercase started with \L or \U
   \n   - A newline
   \t   - A literal tab

Last, but not least the replacement string might contain conditional
replacements with the following syntax (?no:text:other text). This reads as
follows: if the group $no has matched, insert "text", otherwise insert "other
text". "other text" could be skipped and would default to "", that is the
empty string. This is a very powerful feature to add optional text into
snippets.

 4.7.2 Demos:                                                 *UltiSnips-demos*

The transformations are very powerful but yield often a convoluted snippet
syntax. Therefore I offer for each feature a simple example below.

This shows uppercasing one character
------------------- SNIP -------------------
snippet title "Titelize in the Transformation"
${1:a text}
${1/\w+\s*/\u$0/}
endsnippet
------------------- SNAP -------------------
title<tab>big small ->
big small
Big small


This shows uppercasing one character and global replace:
------------------- SNIP -------------------
snippet title "Titelize in the Transformation"
${1:a text}
${1/\w+\s*/\u$0/g}
endsnippet
------------------- SNAP -------------------
title<tab>this is a title ->
this is a title
This Is A Title

This is a clever c-like printf snippet, the second tabstop is only shown
when there is a format (%) character in the first tab stop.
------------------- SNIP -------------------
snippet printf
printf("${1:%s}\n"${1/([^%]|%%)*(%.)?.*/(?2:, :\);)/}$2${1/([^%]|%%)*(%.)?.*/(?2:\);)/}
endsnippet
------------------- SNAP -------------------
printf<tab>Hello<c-j> // End of line ->
printf("Hello\n"); // End of line

But
printf<tab>A is: %s<c-j>A<c-j> // End of line ->
printf("A is: %s\n", A); // End of line


There are many more examples of what can be done with transformations in the
bundled snippets.

 4.8 Clearing snippets                          *UltiSnips-clearing-snippets*

To remove snippets for the current file type, use the "clearsnippets"
directive:
------------------- SNIP -------------------
clearsnippets
------------------- SNAP -------------------

Without arguments, "clearsnippets" removes all snippets defined so far for the
current file type.  UltiSnips travels in reverse along the 'runtimepath', so
"clearsnippets" removes snippet definitions appearing later in the
'runtimepath' than the ".snippets" file in which it's encountered.

Instead of clearing all snippets for the current file type, one or more
individual snippets may be cleared by specifying a space-separated list of
their triggers, e.g.:

------------------- SNIP -------------------
clearsnippets trigger1 trigger2
------------------- SNAP -------------------

This is useful if you only want to override a few triggers or all triggers
that came with UltiSnips with your own definitions. Note that you can
overwrite individual triggers when redefining them using the '!' option
(see |UltiSnips-adding-snippets| for the options).

=============================================================================
5. HELPING OUT                                            *UltiSnips-helping*

UltiSnips needs the help of a vibrant vim community to make it more useful
tomorrow than it is today. Please consider joining this effort by providing
new snippets, new features or bug reports.

You can contribute by fixing or reporting bugs in our issue tracker:
https://bugs.launchpad.net/ultisnips

You can contribute snippets or patches in various ways. Here are the
possibilities in order of convenience for me (please be as convenient as you
can be):

* Clone the repository on launchpad (bzr clone lp:ultisnips), make fixes, push
  the branch and send a merge request on launchpad.
* Clone the repository on GitHub (git clone git@github.com:SirVer/ultisnips.git),
  make your changes and send a pull request on GitHub.
* Make a patch, report a bug/feature request and attach the patch to it.
* Send me an Email with a patch.
* Send me an Email with the changed files only.

If you like this plugin, please also vote for it on its vim script page. It is
life changing for me, maybe it is for you too.
You can find the page here:
http://www.vim.org/scripts/script.php?script_id=2715

=============================================================================
6. CONTACT                                                *UltiSnips-contact*

You can reach me at SirVer -AT- gmx -ADOT- de. You can find the launchpad
project for UltiSnips at https://launchpad.net/ultisnips/, there is also the
bug tracker.

This project aims to be the one-for-all solution for Snippets for Vim. If you
miss a feature or find a bug, please contact me or file a support ticket.

=============================================================================
7. CONTRIBUTORS                                      *UltiSnips-contributors*

UltiSnips is mainly developed by SirVer (Holger Rapp). The following
individuals have contributed code to UltiSnips. In order of apperance.

7.1 Patches & Coding                                 *UltiSnips-contricoding*
--------------------

Contributers are listed in chronological order:

   JCEB - Jan Christoph Ebersbach
   Michael Henry
   Chris Chambers
   Ryan Wooden
   rupa - Rupa Deadwyler
   Timo Schmiade
   blueyed - Daniel Hahler
   expelledboy - Anthony Jackson
   allait - Alexey Bezhan
   peacech - Charles Gunawan
   guns - Sung Pae
   shlomif - Shlomi Fish
   pberndt - Phillip Berndt
   thanatermesis-elive - Thanatermesis
   rico-ambiescent - Rico Sta. Cruz
   Cody Frazer 

7.2 Snippets                                       *UltiSnips-contrisnippets*
------------

Contributers are listed in chronological order:

   Alec Thomas
   Ryan Wooden
   Ches Martin
   Gordin (g0rdin)
   Jan Mollowitz (phux)
   Georgi Valkov (gvalkov)
   Miek Gieben (miek)
   Aldis Berjoza (graudeejs)

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