Commit 5ba75c80 authored by Richard M. Stallman's avatar Richard M. Stallman

(Indentation): Condense, simplify, clarify prev change.

parent f9ad161b
......@@ -40,75 +40,47 @@ be called `indentation':
@enumerate
@item
The most simple operation is to just insert a tab character. This
operation does not have a convenient key binding, because it is
subsumed by the more general operation described next. But you can use
@kbd{C-q @key{TAB}} to insert a literal tab character.
Insert a tab character. You can type @kbd{C-q @key{TAB}} to do this.
A tab character is displayed as a stretch of whitespace which extends
to the next display tab stop position, and the default width of a tab
stop is eight. @xref{Display Custom}, for more details.
@item
Emacs also supports tab stops. You can set them at arbitrary
positions, and then use @kbd{M-i} to advance to the next tab stop. The
default tab stop list contains positions (columns) that are a multiple
of eight, and so the effect of @kbd{M-i} is the same as that of
@kbd{C-q @key{TAB}} in the default case.
You can set the tab stops with @kbd{M-x edit-tab-stops}.
Advance to the next tab stop. You can set tab stops at your choice of
column positions, then type @kbd{M-i} to advance to the next tab stop.
The default is to have tab stops every eight columns, which means by
default @kbd{M-i} inserts a tab character. To set the tab stops, use
@kbd{M-x edit-tab-stops}.
@item
You can align successive lines with each other. This is called
@dfn{relative indentation} in Emacs and is performed by the command
@kbd{M-x indent-relative}. The effect is best shown by an example:
@example
This shows the effect of relative indentation.
^ ^ ^ ^ ^ ^ ^
@end example
The positions for the @code{^} characters on the second line were
obtained using @kbd{M-x indent-relative}.
In Fundamental mode and in Text mode, @key{TAB} runs the command
@code{indent-relative}.
Align a line with the previous line. More precisely, the command
@kbd{M-x indent-relative} indents the current line under the beginning
of some word in the previous line. In Fundamental mode and in Text
mode, @key{TAB} runs the command @code{indent-relative}.
@item
The most sophisticated method is called @dfn{syntax-driven indentation}
and is the default behavior of the @key{TAB} key in Emacs.
Most programming languages have some indentation convention. For Lisp
code, lines are indented according to their nesting in parentheses. The
same general idea is used for C code, though many details are different.
For some languages, different kinds of indentation styles are
commonly used. Emacs accomodates this by allowing users to customize
the indentation. For example, see @ref{Customizing Indentation,,,ccmode},
for a description of these facilities for the C language.
The most sophisticated method is @dfn{syntax-driven indentation}.
Most programming languages have an indentation convention. For Lisp
code, lines are indented according to their nesting in parentheses. C
code uses the same general idea, but many details are different.
@kindex TAB
Whatever the language, to indent a line, use the @key{TAB} command. Each
major mode defines this command to perform the sort of indentation
appropriate for the particular language. In Lisp mode, @key{TAB} aligns
the line according to its depth in parentheses. No matter where in the
line you are when you type @key{TAB}, it aligns the line as a whole. In C
mode, @key{TAB} implements a subtle and sophisticated indentation style that
knows about many aspects of C syntax.
Type @key{TAB} to do syntax-driven indentation, in a mode that
supports it. It realigns the current line according with the syntax
of the preceding lines. No matter where in the line you are when you
type @key{TAB}, it aligns the line as a whole.
@end enumerate
Normally, all of the above methods insert an optimal mix of tabs and
spaces for the needed indentation. @xref{Just Spaces}, for how to
prevent use of tabs. However, the first method (@kbd{C-q @key{TAB}})
always inserts a tab, even if you prevented their use.
spaces to align to the desired column. @xref{Just Spaces}, for how to
disable use of tabs. However, @kbd{C-q @key{TAB}} always inserts a
tab, even they are disabled for the indentation commands.
@c In Text mode, @key{TAB} runs the command @code{tab-to-tab-stop}, which
@c indents to the next tab stop column. You can set the tab stops with
@c @kbd{M-x edit-tab-stops}.
@c Normally, @key{TAB} inserts an optimal mix of tabs and spaces for
@c the intended indentation. @xref{Just Spaces}, for how to prevent use
@c of tabs.
@menu
* Indentation Commands:: Various commands and techniques for indentation.
* Tab Stops:: You can set arbitrary "tab stops" and then
......
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