runtime/doc/indent.txt

*indent.txt*    For Vim version 7.2a.  Last change: 2008 Jun 21


		  VIM REFERENCE MANUAL    by Bram Moolenaar


This file is about indenting C programs and other files.

1. Indenting C style programs	|C-indenting|
2. Indenting by expression	|indent-expression|

==============================================================================
1. Indenting C style programs				*C-indenting*

The basics for C style indenting are explained in section |30.2| of the user
manual.

Vim has options for automatically indenting C style program files. Many
programming languages including Java and C++ follow very closely the
formatting conventions established with C.  These options affect only the
indent and do not perform other formatting.  There are additional options that
affect other kinds of formatting as well as indenting, see |format-comments|,
|fo-table|, |gq| and |formatting| for the main ones.

Note that this will not work when the |+smartindent| or |+cindent| features
have been disabled at compile time.

There are in fact four main methods available for indentation, each one
overrides the previous if it is enabled, or non-empty for 'indentexpr':
'autoindent'	uses the indent from the previous line.
'smartindent'	is like 'autoindent' but also recognizes some C syntax to
		increase/reduce the indent where appropriate.
'cindent'	Works more cleverly than the other two and is configurable to
		different indenting styles.
'indentexpr'	The most flexible of all: Evaluates an expression to compute
		the indent of a line.  When non-empty this method overrides
		the other ones.  See |indent-expression|.
The rest of this section describes the 'cindent' option.

Note that 'cindent' indenting does not work for every code scenario.  Vim
is not a C compiler: it does not recognize all syntax.  One requirement is
that toplevel functions have a '{' in the first column.  Otherwise they are
easily confused with declarations.

These four options control C program indenting:
'cindent'	Enables Vim to perform C program indenting automatically.
'cinkeys'	Specifies which keys trigger reindenting in insert mode.
'cinoptions'	Sets your preferred indent style.
'cinwords'	Defines keywords that start an extra indent in the next line.

If 'lisp' is not on and 'equalprg' is empty, the "=" operator indents using
Vim's built-in algorithm rather than calling an external program.

See |autocommand| for how to set the 'cindent' option automatically for C code
files and reset it for others.

					*cinkeys-format* *indentkeys-format*
The 'cinkeys' option is a string that controls Vim's indenting in response to
typing certain characters or commands in certain contexts.  Note that this not
only triggers C-indenting.  When 'indentexpr' is not empty 'indentkeys' is
used instead.  The format of 'cinkeys' and 'indentkeys' is equal.

The default is "0{,0},0),:,0#,!^F,o,O,e" which specifies that indenting occurs
as follows:

	"0{"	if you type '{' as the first character in a line
	"0}"	if you type '}' as the first character in a line
	"0)"	if you type ')' as the first character in a line
	":"	if you type ':' after a label or case statement
	"0#"	if you type '#' as the first character in a line
	"!^F"	if you type CTRL-F (which is not inserted)
	"o"	if you type a <CR> anywhere or use the "o" command (not in
		insert mode!)
	"O"	if you use the "O" command (not in insert mode!)
	"e"	if you type the second 'e' for an "else" at the start of a
		line

Characters that can precede each key:				*i_CTRL-F*
!	When a '!' precedes the key, Vim will not insert the key but will
	instead reindent the current line.  This allows you to define a
	command key for reindenting the current line.  CTRL-F is the default
	key for this.  Be careful if you define CTRL-I for this because CTRL-I
	is the ASCII code for <Tab>.
*	When a '*' precedes the key, Vim will reindent the line before
	inserting the key.  If 'cinkeys' contains "*<Return>", Vim reindents
	the current line before opening a new line.
0	When a zero precedes the key (but appears after '!' or '*') Vim will
	reindent the line only if the key is the first character you type in
	the line.  When used before "=" Vim will only reindent the line if
	there is only white space before the word.

When neither '!' nor '*' precedes the key, Vim reindents the line after you
type the key.  So ';' sets the indentation of a line which includes the ';'.

Special key names:
<>	Angle brackets mean spelled-out names of keys.  For example: "<Up>",
	"<Ins>" (see |key-notation|).
^	Letters preceded by a caret (^) are control characters.  For example:
	"^F" is CTRL-F.
o	Reindent a line when you use the "o" command or when Vim opens a new
	line below the current one (e.g., when you type <Enter> in insert
	mode).
O	Reindent a line when you use the "O" command.
e	Reindent a line that starts with "else" when you type the second 'e'.
:	Reindent a line when a ':' is typed which is after a label or case
	statement.  Don't reindent for a ":" in "class::method" for C++.  To
	Reindent for any ":", use "<:>".
=word	Reindent when typing the last character of "word".  "word" may
	actually be part of another word.  Thus "=end" would cause reindenting
	when typing the "d" in "endif" or "endwhile".  But not when typing
	"bend".  Also reindent when completion produces a word that starts
	with "word".  "0=word" reindents when there is only white space before
	the word.
=~word	Like =word, but ignore case.

If you really want to reindent when you type 'o', 'O', 'e', '0', '<', '>',
'*', ':' or '!', use "<o>", "<O>", "<e>", "<0>", "<<>", "<>>", "<*>", "<:>" or
"<!>", respectively, for those keys.

For an emacs-style indent mode where lines aren't indented every time you
press <Enter> but only if you press <Tab>, I suggest:
	:set cinkeys=0{,0},:,0#,!<Tab>,!^F
You might also want to switch off 'autoindent' then.

Note: If you change the current line's indentation manually, Vim ignores the
cindent settings for that line.  This prevents vim from reindenting after you
have changed the indent by typing <BS>, <Tab>, or <Space> in the indent or
used CTRL-T or CTRL-D.

						*cinoptions-values*
The 'cinoptions' option sets how Vim performs indentation.  In the list below,
"N" represents a number of your choice (the number can be negative).  When
there is an 's' after the number, Vim multiplies the number by 'shiftwidth':
"1s" is 'shiftwidth', "2s" is two times 'shiftwidth', etc.  You can use a
decimal point, too: "-0.5s" is minus half a 'shiftwidth'.  The examples below
assume a 'shiftwidth' of 4.

	>N    Amount added for "normal" indent.  Used after a line that should
	      increase the indent (lines starting with "if", an opening brace,
	      etc.).  (default 'shiftwidth').

		cino=		    cino=>2		cino=>2s >
		  if (cond)	      if (cond)		  if (cond)
		  {		      {			  {
		      foo;		foo;			  foo;
		  }		      }			  }
<
	eN    Add N to the prevailing indent inside a set of braces if the
	      opening brace at the End of the line (more precise: is not the
	      first character in a line).  This is useful if you want a
	      different indent when the '{' is at the start of the line from
	      when '{' is at the end of the line.  (default 0).

		cino=		    cino=e2		cino=e-2 >
		  if (cond) {	      if (cond) {	  if (cond) {
		      foo;		    foo;	    foo;
		  }		      }			  }
		  else		      else		  else
		  {		      {			  {
		      bar;		  bar;		      bar;
		  }		      }			  }
<
	nN    Add N to the prevailing indent for a statement after an "if",
	      "while", etc., if it is NOT inside a set of braces.  This is
	      useful if you want a different indent when there is no '{'
	      before the statement from when there is a '{' before it.
	      (default 0).

		cino=		    cino=n2		cino=n-2 >
		  if (cond)	      if (cond)		  if (cond)
		      foo;		    foo;	    foo;
		  else		      else		  else
		  {		      {			  {
		      bar;		  bar;		      bar;
		  }		      }			  }
<
	fN    Place the first opening brace of a function or other block in
	      column N.  This applies only for an opening brace that is not
	      inside other braces and is at the start of the line.  What comes
	      after the brace is put relative to this brace.  (default 0).

		cino=		    cino=f.5s		cino=f1s >
		  func()	      func()		  func()
		  {			{		      {
		      int foo;		    int foo;		  int foo;
<
	{N    Place opening braces N characters from the prevailing indent.
	      This applies only for opening braces that are inside other
	      braces.  (default 0).

		cino=		    cino={.5s		cino={1s >
		  if (cond)	      if (cond)		  if (cond)
		  {			{		      {
		      foo;		  foo;		      foo;
<
	}N    Place closing braces N characters from the matching opening
	      brace.  (default 0).

		cino=		    cino={2,}-0.5s	cino=}2 >
		  if (cond)	      if (cond)		  if (cond)
		  {			{		  {
		      foo;		  foo;		      foo;
		  }		      }			    }
<
	^N    Add N to the prevailing indent inside a set of braces if the
	      opening brace is in column 0.  This can specify a different
	      indent for whole of a function (some may like to set it to a
	      negative number).  (default 0).

		cino=		    cino=^-2		cino=^-s >
		  func()	      func()		  func()
		  {		      {			  {
		      if (cond)		if (cond)	  if (cond)
		      {			{		  {
			  a = b;	    a = b;	      a = b;
		      }			}		  }
		  }		      }			  }
<
	:N    Place case labels N characters from the indent of the switch().
	      (default 'shiftwidth').

		cino=		    cino=:0 >
		  switch (x)	      switch(x)
		  {		      {
		      case 1:	      case 1:
			  a = b;	  a = b;
		      default:	      default:
		  }		      }
<
	=N    Place statements occurring after a case label N characters from
	      the indent of the label.  (default 'shiftwidth').

		cino=		    cino==10 >
		   case 11:		case 11:  a = a + 1;
		       a = a + 1;		  b = b + 1;
<
	lN    If N != 0 Vim will align with a case label instead of the
	      statement after it in the same line.

		cino=			    cino=l1 >
		    switch (a) {	      switch (a) {
			case 1: {		  case 1: {
				    break;	      break;
				}		  }
<
	bN    If N != 0 Vim will align a final "break" with the case label,
	      so that case..break looks like a sort of block.  (default: 0).

		cino=		    cino=b1 >
		  switch (x)	      switch(x)
		  {		      {
		      case 1:		  case 1:
			  a = b;	      a = b;
			  break;	  break;

		      default:		  default:
			  a = 0;	      a = 0;
			  break;	  break;
		  }		      }
<
	gN    Place C++ scope declarations N characters from the indent of the
	      block they are in.  (default 'shiftwidth').  A scope declaration
	      can be "public:", "protected:" or "private:".

		cino=		    cino=g0 >
		  {		      {
		      public:	      public:
			  a = b;	  a = b;
		      private:	      private:
		  }		      }
<
	hN    Place statements occurring after a C++ scope declaration N
	      characters from the indent of the label.  (default
	      'shiftwidth').

		cino=		    cino=h10 >
		   public:		public:   a = a + 1;
		       a = a + 1;		  b = b + 1;
<
	pN    Parameter declarations for K&R-style function declarations will
	      be indented N characters from the margin.  (default
	      'shiftwidth').

		cino=		    cino=p0		cino=p2s >
		  func(a, b)	      func(a, b)	  func(a, b)
		      int a;	      int a;			  int a;
		      char b;	      char b;			  char b;
<
	tN    Indent a function return type declaration N characters from the
	      margin.  (default 'shiftwidth').

		cino=		    cino=t0		cino=t7 >
		      int	      int			 int
		  func()	      func()		  func()
<
	iN    Indent C++ base class declarations and constructor
	      initializations, if they start in a new line (otherwise they
	      are aligned at the right side of the ':').
	      (default 'shiftwidth').

		cino=			  cino=i0 >
		  class MyClass :	    class MyClass :
		      public BaseClass      public BaseClass
		  {}			    {}
		  MyClass::MyClass() :	    MyClass::MyClass() :
		      BaseClass(3)	    BaseClass(3)
		  {}			    {}
<
	+N    Indent a continuation line (a line that spills onto the next) N
	      additional characters.  (default 'shiftwidth').

		cino=			  cino=+10 >
		  a = b + 9 *		    a = b + 9 *
		      c;			      c;
<
	cN    Indent comment lines after the comment opener, when there is no
	      other text with which to align, N characters from the comment
	      opener.  (default 3).  See also |format-comments|.

		cino=			  cino=c5 >
		  /*			    /*
		     text.			 text.
		   */			     */
<
	CN    When N is non-zero, indent comment lines by the amount specified
	      with the c flag above even if there is other text behind the
	      comment opener.  (default 0).

		cino=c0			  cino=c0,C1 >
		  /********		    /********
		    text.		    text.
		  ********/		    ********/
<	      (Example uses ":set comments& comments-=s1:/* comments^=s0:/*")

	/N    Indent comment lines N characters extra.  (default 0).
		cino=			  cino=/4 >
		  a = b;		    a = b;
		  /* comment */			/* comment */
		  c = d;		    c = d;
<
	(N    When in unclosed parentheses, indent N characters from the line
	      with the unclosed parentheses.  Add a 'shiftwidth' for every
	      unclosed parentheses.  When N is 0 or the unclosed parentheses
	      is the first non-white character in its line, line up with the
	      next non-white character after the unclosed parentheses.
	      (default 'shiftwidth' * 2).

		cino=			  cino=(0 >
		  if (c1 && (c2 ||	    if (c1 && (c2 ||
			      c3))		       c3))
		      foo;			foo;
		  if (c1 &&		    if (c1 &&
			  (c2 || c3))		(c2 || c3))
		     {			       {
<
	uN    Same as (N, but for one level deeper.  (default 'shiftwidth').

		cino=			  cino=u2 >
		  if (c123456789	    if (c123456789
			  && (c22345		    && (c22345
			      || c3))		      || c3))
<
	UN    When N is non-zero, do not ignore the indenting specified by
	      ( or u in case that the unclosed parentheses is the first
	      non-white character in its line.  (default 0).

		cino= or cino=(s	  cino=(s,U1 >
		  c = c1 &&		    c = c1 &&
		      (				(
		       c2 ||			    c2 ||
		       c3			    c3
		      ) && c4;			) && c4;
<
	wN    When in unclosed parentheses and N is non-zero and either
	      using "(0" or "u0", respectively, or using "U0" and the unclosed
	      parentheses is the first non-white character in its line, line
	      up with the character immediately after the unclosed parentheses
	      rather than the first non-white character.  (default 0).

		cino=(0			  cino=(0,w1 >
		  if (   c1		    if (   c1
			 && (   c2		&& (   c2
				|| c3))		    || c3))
		      foo;			foo;
<
	WN    When in unclosed parentheses and N is non-zero and either
	      using "(0" or "u0", respectively and the unclosed parentheses is
	      the last non-white character in its line and it is not the
	      closing parentheses, indent the following line N characters
	      relative to the outer context (i.e. start of the line or the
	      next unclosed parentheses).  (default: 0).

		cino=(0			   cino=(0,W4 >
		  a_long_line(		    a_long_line(
			      argument,		argument,
			      argument);	argument);
		  a_short_line(argument,    a_short_line(argument,
			       argument);		 argument);
<
	mN    When N is non-zero, line up a line starting with a closing
	      parentheses with the first character of the line with the
	      matching opening parentheses.  (default 0).

		cino=(s			  cino=(s,m1 >
		  c = c1 && (		    c = c1 && (
		      c2 ||			c2 ||
		      c3			c3
		      ) && c4;		    ) && c4;
		  if (			    if (
		      c1 && c2			c1 && c2
		     )			    )
		      foo;			foo;
<
	MN    When N is non-zero, line up a line starting with a closing
	      parentheses with the first character of the previous line.
	      (default 0).

		cino=			  cino=M1 >
		  if (cond1 &&		    if (cond1 &&
			 cond2			   cond2
		     )				   )
<
					*java-cinoptions* *java-indenting*
	jN    Indent java anonymous classes correctly.  The value 'N' is
	      currently unused but must be non-zero (e.g. 'j1').  'j1' will
	      indent for example the following code snippet correctly: >

		object.add(new ChangeListener() {
		    public void stateChanged(ChangeEvent e) {
			do_something();
		    }
		});
<
	)N    Vim searches for unclosed parentheses at most N lines away.
	      This limits the time needed to search for parentheses.  (default
	      20 lines).

	*N    Vim searches for unclosed comments at most N lines away.  This
	      limits the time needed to search for the start of a comment.
	      (default 30 lines).

	#N    When N is non-zero recognize shell/Perl comments, starting with
	      '#'.  Default N is zero: don't recognizes '#' comments.  Note
	      that lines starting with # will still be seen as preprocessor
	      lines.


The defaults, spelled out in full, are:
	cinoptions=>s,e0,n0,f0,{0,}0,^0,:s,=s,l0,b0,gs,hs,ps,ts,is,+s,c3,C0,
		   /0,(2s,us,U0,w0,W0,m0,j0,)20,*30,#0

Vim puts a line in column 1 if:
- It starts with '#' (preprocessor directives), if 'cinkeys' contains '#'.
- It starts with a label (a keyword followed by ':', other than "case" and
  "default").
- Any combination of indentations causes the line to have less than 0
  indentation.

==============================================================================
2. Indenting by expression				*indent-expression*

The basics for using flexible indenting are explained in section |30.3| of the
user manual.

If you want to write your own indent file, it must set the 'indentexpr'
option.  Setting the 'indentkeys' option is often useful.  See the
$VIMRUNTIME/indent directory for examples.


REMARKS ABOUT SPECIFIC INDENT FILES ~


FORTRAN							*ft-fortran-indent*

Block if, select case, and where constructs are indented.  Comments, labelled
statements and continuation lines are indented if the Fortran is in free
source form, whereas they are not indented if the Fortran is in fixed source
form because of the left margin requirements.  Hence manual indent corrections
will be necessary for labelled statements and continuation lines when fixed
source form is being used.  For further discussion of the method used for the
detection of source format see |ft-fortran-syntax|.

Do loops ~
All do loops are left unindented by default.  Do loops can be unstructured in
Fortran with (possibly multiple) loops ending on a labelled executable
statement of almost arbitrary type.  Correct indentation requires
compiler-quality parsing.  Old code with do loops ending on labelled statements
of arbitrary type can be indented with elaborate programs such as Tidy
(http://www.unb.ca/chem/ajit/f_tidy.htm).  Structured do/continue loops are
also left unindented because continue statements are also used for purposes
other than ending a do loop.  Programs such as Tidy can convert structured
do/continue loops to the do/enddo form.  Do loops of the do/enddo variety can
be indented.  If you use only structured loops of the do/enddo form, you should
declare this by setting the fortran_do_enddo variable in your .vimrc as
follows >

   let fortran_do_enddo=1

in which case do loops will be indented.  If all your loops are of do/enddo
type only in, say, .f90 files, then you should set a buffer flag with an
autocommand such as >

  au! BufRead,BufNewFile *.f90 let b:fortran_do_enddo=1

to get do loops indented in .f90 files and left alone in Fortran files with
other extensions such as .for.


PYTHON							*ft-python-indent*

The amount of indent can be set for the following situations.  The examples
given are de the defaults.  Note that the variables are set to an expression,
so that you can change the value of 'shiftwidth' later.

Indent after an open paren: >
	let g:pyindent_open_paren = '&sw * 2'
Indent after a nested paren: >
	let g:pyindent_nested_paren = '&sw'
Indent for a continuation line: >
	let g:pyindent_continue = '&sw * 2'


SHELL							*ft-sh-indent*

The amount of indent applied under various circumstances in a shell file can
be configured by setting the following keys in the |Dictionary|
b:sh_indent_defaults to a specific amount or to a |Funcref| that references a
function that will return the amount desired:

b:sh_indent_options['default']	Default amount of indent.

b:sh_indent_options['continuation-line']
				Amount of indent to add to a continued line.

b:sh_indent_options['case-labels']
				Amount of indent to add for case labels.

b:sh_indent_options['case-statement']
				Amount of indent to add for case statements.

b:sh_indent_options['case-breaks']
				Amount of indent to add (or more likely
				remove) for case breaks.

VERILOG							*ft-verilog-indent*

General block statements such as if, for, case, always, initial, function,
specify and begin, etc., are indented.  The module block statements (first
level blocks) are not indented by default.  you can turn on the indent with
setting a variable in the .vimrc as follows: >

  let b:verilog_indent_modules = 1

then the module blocks will be indented.  To stop this, remove the variable: >

  :unlet b:verilog_indent_modules

To set the variable only for Verilog file.  The following statements can be
used: >

  au BufReadPost * if exists("b:current_syntax")
  au BufReadPost *   if b:current_syntax == "verilog"
  au BufReadPost *     let b:verilog_indent_modules = 1
  au BufReadPost *   endif
  au BufReadPost * endif

Furthermore, setting the variable b:verilog_indent_width to change the
indenting width (default is 'shiftwidth'): >

  let b:verilog_indent_width = 4
  let b:verilog_indent_width = &sw * 2

In addition, you can turn the verbose mode for debug issue: >

  let b:verilog_indent_verbose = 1

Make sure to do ":set cmdheight=2" first to allow the display of the message.


VHDL							*ft-vhdl-indent*

Alignment of generic/port mapping statements are performed by default. This
causes the following alignment example: >

  ENTITY sync IS
  PORT (
         clk        : IN  STD_LOGIC;
         reset_n    : IN  STD_LOGIC;
         data_input : IN  STD_LOGIC;
         data_out   : OUT STD_LOGIC
       );
  END ENTITY sync;

To turn this off, add >

  let g:vhdl_indent_genportmap = 0

to the .vimrc file, which causes the previous alignment example to change: >

  ENTITY sync IS
  PORT (
    clk        : IN  STD_LOGIC;
    reset_n    : IN  STD_LOGIC;
    data_input : IN  STD_LOGIC;
    data_out   : OUT STD_LOGIC
  );
  END ENTITY sync;

----------------------------------------

Alignment of right-hand side assignment "<=" statements are performed by
default. This causes the following alignment example: >

  sig_out <= (bus_a(1) AND
             (sig_b OR sig_c)) OR
             (bus_a(0) AND sig_d);

To turn this off, add >

  let g:vhdl_indent_rhsassign = 0

to the .vimrc file, which causes the previous alignment example to change: >

  sig_out <= (bus_a(1) AND
    (sig_b OR sig_c)) OR
    (bus_a(0) AND sig_d);

----------------------------------------

Full-line comments (lines that begin with "--") are indented to be aligned with
the very previous line's comment, PROVIDED that a whitespace follows after
"--".

For example: >

  sig_a <= sig_b; -- start of a comment
                  -- continuation of the comment
                  -- more of the same comment

While in Insert mode, after typing "-- " (note the space " "), hitting CTRL-F
will align the current "-- " with the previous line's "--".

If the very previous line does not contain "--", THEN the full-line comment
will be aligned with the start of the next non-blank line that is NOT a
full-line comment.

Indenting the following code: >

  sig_c <= sig_d; -- comment 0
         -- comment 1
               -- comment 2
    --debug_code:
    --PROCESS(debug_in)
         --BEGIN
            --  FOR i IN 15 DOWNTO 0 LOOP
             --    debug_out(8*i+7 DOWNTO 8*i) <= debug_in(15-i);
            --  END LOOP;
     --END PROCESS debug_code;

      -- comment 3
  sig_e <= sig_f; -- comment 4
           -- comment 5

results in: >

  sig_c <= sig_d; -- comment 0
                  -- comment 1
                  -- comment 2
  --debug_code:
  --PROCESS(debug_in)
  --BEGIN
  --  FOR i IN 15 DOWNTO 0 LOOP
  --    debug_out(8*i+7 DOWNTO 8*i) <= debug_in(15-i);
  --  END LOOP;
  --END PROCESS debug_code;

  -- comment 3
  sig_e <= sig_f; -- comment 4
                  -- comment 5

Notice that "--debug_code:" does not align with "-- comment 2"
because there is no whitespace that follows after "--" in "--debug_code:".

Given the dynamic nature of indenting comments, indenting should be done TWICE.
On the first pass, code will be indented. On the second pass, full-line
comments will be indented according to the correctly indented code.


VIM							*ft-vim-indent*

For indenting Vim scripts there is one variable that specifies the amount of
indent for a continuation line, a line that starts with a backslash: >

	:let g:vim_indent_cont = &sw * 3

Three times shiftwidth is the default value.


 vim:tw=78:ts=8:ft=help:norl: