path: root/runtime/doc/indent.txt

*indent.txt*    For Vim version 7.4.  Last change: 2013 Aug 03


		  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.  The value after
the option character can be one of these (N is any number):
	N	indent N spaces
	-N	indent N spaces to the left
	Ns	N times 'shiftwidth' spaces
	-Ns	N times 'shiftwidth' spaces to the left

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.
							*cino->*
	>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;
		  }		      }			  }
<
							*cino-e*
	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;
		  }		      }			  }
<
							*cino-n*
	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;
		  }		      }			  }
<
							*cino-f*
	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;
<
							*cino-{*
	{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;
<
							*cino-}*
	}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;
		  }		      }			    }
<
							*cino-^*
	^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;
		      }			}		  }
		  }		      }			  }
<
							*cino-L*
	LN    Controls placement of jump labels. If N is negative, the label
	      will be placed at column 1. If N is non-negative, the indent of
	      the label will be the prevailing indent minus N.  (default -1).

		cino=               cino=L2             cino=Ls >
		  func()              func()              func()
		  {                   {                   {
		      {                   {                   {
		          stmt;               stmt;               stmt;
		  LABEL:                    LABEL:            LABEL:
		      }                   }                   }
		  }                   }                   }
<
							*cino-:*
	: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:
		  }		      }
<
							*cino-=*
	=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;
<
							*cino-l*
	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;
				}		  }
<
							*cino-b*
	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).
	      When using 1, consider adding "0=break" to 'cinkeys'.

		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;
		  }		      }
<
							*cino-g*
	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:
		  }		      }
<
							*cino-h*
	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;
<
							*cino-N*
	NN    Indent inside C++ namespace N characters extra compared to a
	      normal block.  (default 0).

		cino=			   cino=N-s >
		  namespace {                namespace {
		      void function();       void function();
		  }                          }

		  namespace my               namespace my
		  {                          {
		      void function();       void function();
		  }                          }
<
							*cino-p*
	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;
<
							*cino-t*
	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()
<
							*cino-i*
	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)
		  {}			    {}
<
							*cino-+*
	+N    Indent a continuation line (a line that spills onto the next)
              inside a function N additional characters.  (default
              'shiftwidth').
              Outside of a function, when the previous line ended in a
              backslash, the 2 * N is used.

		cino=			  cino=+10 >
		  a = b + 9 *		    a = b + 9 *
		      c;			      c;
<
							*cino-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.
		   */			     */
<
							*cino-C*
	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:/*")

							*cino-/*
	/N    Indent comment lines N characters extra.  (default 0).
		cino=			  cino=/4 >
		  a = b;		    a = b;
		  /* comment */			/* comment */
		  c = d;		    c = d;
<
							*cino-(*
	(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))
		     {			       {
<
							*cino-u*
	uN    Same as (N, but for one level deeper.  (default 'shiftwidth').

		cino=			  cino=u2 >
		  if (c123456789	    if (c123456789
			  && (c22345		    && (c22345
			      || c3))		      || c3))
<
							*cino-U*
	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;
<
							*cino-w*
	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;
<
							*cino-W*
	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);
<
							*cino-k*
	kN    When in unclosed parentheses which follow "if", "for" or
	      "while" and N is non-zero, overrides the behaviour defined by
	      "(N": causes the indent to be N characters relative to the outer
	      context (i.e. the line where "if", "for" or "while" is).  Has
	      no effect on deeper levels of nesting.  Affects flags like "wN"
	      only for the "if", "for" and "while" conditions.  If 0, defaults
	      to behaviour defined by the "(N" flag.  (default: 0).

		cino=(0			   cino=(0,ks >
		  if (condition1	    if (condition1
		      && condition2)		    && condition2)
		      action();			action();
		  function(argument1	    function(argument1