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Info file emacs, produced by texinfo-format-buffer -*-Text-*- from file emacs.tex This file documents the GNU Emacs editor. Copyright (C) 1985, 1986 Richard M. Stallman. Permission is granted to make and distribute verbatim copies of this manual provided the copyright notice and this permission notice are preserved on all copies. Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided also that the sections entitled "The GNU Manifesto", "Distribution" and "GNU Emacs General Public License" are included exactly as in the original, and provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one. Permission is granted to copy and distribute translations of this manual into another language, under the above conditions for modified versions, except that the sections entitled "The GNU Manifesto", "Distribution" and "GNU Emacs General Public License" may be included in a translation approved by the author instead of in the original English. File: emacs Node: Defuns, Prev: Lists, Up: Programs, Next: Grinding Defuns ====== In Emacs, a parenthetical grouping at the top level in the buffer is called a "defun". The name derives from the fact that most top-level lists in a Lisp file are instances of the special form `defun', but any top-level parenthetical grouping counts as a defun in Emacs parlance regardless of what its contents are, and regardless of the programming language in use. For example, in C, the body of a function definition is a defun. `C-M-a' Move to beginning of current or preceding defun (`beginning-of-defun'). `C-M-e' Move to end of current or following defun (`end-of-defun'). `C-M-h' Put region around whole current or following defun (`mark-defun'). The commands to move to the beginning and end of the current defun are `C-M-a' (`beginning-of-defun') and `C-M-e' (`end-of-defun'). If you wish to operate on the current defun, use `C-M-h' (`mark-defun') which puts point at the beginning and mark at the end of the current or next defun. For example, this is the easiest way to get ready to move the defun to a different place in the text. In C mode, `C-M-h' runs the function `mark-c-function', which is almost the same as `mark-defun'; the difference is that it backs up over the argument declarations, function name and returned data type so that the entire C function is inside the region. Emacs assumes that any open-parenthesis found in the leftmost column is the start of a defun. Therefore, never put an open-parenthesis at the left margin in a Lisp file unless it is the start of a top level list. Never put an open-brace or other opening delimiter at the beginning of a line of C code unless it starts the body of a function. The most likely problem case is when you want an opening delimiter at the start of a line inside a string. To avoid trouble, put an escape character (`\', in C and Emacs Lisp, `/' in some other Lisp dialects) before the opening delimiter. It will not affect the contents of the string. In the remotest past, the original Emacs found defuns by moving upward a level of parentheses until there were no more levels to go up. This always required scanning all the way back to the beginning of the buffer, even for a small function. To speed up the operation, Emacs was changed to assume that any `(' (or other character assigned the syntactic class of opening-delimiter) at the left margin is the start of a defun. This heuristic was nearly always right and avoided the costly scan; however, it mandated the convention described above. File: emacs Node: Grinding, Prev: Defuns, Up: Programs, Next: Matching Indentation for Programs ======================== The best way to keep a program properly indented ("ground") is to use Emacs to re-indent it as you change it. Emacs has commands to indent properly either a single line, a specified number of lines, or all of the lines inside a single parenthetical grouping. * Menu: * Basic Indent:: * Multi-line Indent:: Commands to reindent many lines at once. * Lisp Indent:: Specifying how each Lisp function should be indented. * C Indent:: Choosing an indentation style for C code. File: emacs Node: Basic Indent, Prev: Grinding, Up: Grinding, Next: Multi-line Indent Basic Program Indentation Commands ---------------------------------- `TAB' Adjust indentation of current line. `LFD' Equivalent to RET followed by TAB (`newline-and-indent'). The basic indentation command is TAB, which gives the current line the correct indentation as determined from the previous lines. The function that TAB runs depends on the major mode; it is `lisp-indent-line' in Lisp mode, `c-indent-line' in C mode, etc. These functions understand different syntaxes for different languages, but they all do about the same thing. TAB in any programming language major mode inserts or deletes whitespace at the beginning of the current line, independent of where point is in the line. If point is inside the whitespace at the beginning of the line, TAB leaves it at the end of that whitespace; otherwise, TAB leaves point fixed with respect to the characters around it. Use `C-q TAB' to insert a tab at point. When entering a large amount of new code, use LFD (`newline-and-indent'), which is equivalent to a RET followed by a TAB. LFD creates a blank line, and then gives it the appropriate indentation. TAB indents the second and following lines of the body of an parenthetical grouping each under the preceding one; therefore, if you alter one line's indentation to be nonstandard, the lines below will tend to follow it. This is the right behavior in cases where the standard result of TAB is unaesthetic. Remember that an open-parenthesis, open-brace or other opening delimiter at the left margin is assumed by Emacs (including the indentation routines) to be the start of a function. Therefore, you must never have an opening delimiter in column zero that is not the beginning of a function, not even inside a string. This restriction is vital for making the indentation commands fast; you must simply accept it. *Note Defuns::, for more information on this. File: emacs Node: Multi-line Indent, Prev: Basic Indent, Up: Grinding, Next: Lisp Indent Indenting Several Lines ----------------------- When you wish to re-indent several lines of code which have been altered or moved to a different level in the list structure, you have several commands available. `C-M-q' Re-indent all the lines within one list (`indent-sexp'). `C-u TAB' Shift an entire list rigidly sideways so that its first line is properly indented. `C-M-\' Re-indent all lines in the region (`indent-region'). You can re-indent the contents of a single list by positioning point before the beginning of it and typing `C-M-q' (`indent-sexp' in Lisp mode, `indent-c-exp' in C mode; also bound to other suitable functions in other modes). The indentation of the line the sexp starts on is not changed; therefore, only the relative indentation within the list, and not its position, is changed. To correct the position as well, type a TAB before the `C-M-q'. If the relative indentation within a list is correct but the indentation of its beginning is not, go to the line the list begins on and type `C-u TAB'. When TAB is given a numeric argument, it moves all the lines in the grouping starting on the current line sideways the same amount that the current line moves. It is clever, though, and does not move lines that start inside strings, or C preprocessor lines when in C mode. Another way to specify the range to be re-indented is with point and mark. The command `C-M-\' (`indent-region') applies TAB to every line whose first character is between point and mark. File: emacs Node: Lisp Indent, Prev: Multi-line Indent, Up: Grinding, Next: C Indent Customizing Lisp Indentation ---------------------------- The indentation pattern for a Lisp expression can depend on the function called by the expression. For each Lisp function, you can choose among several predefined patterns of indentation, or define an arbitrary one with a Lisp program. The standard pattern of indentation is as follows: the second line of the expression is indented under the first argument, if that is on the same line as the beginning of the expression; otherwise, the second line is indented underneath the function name. Each following line is indented under the previous line whose nesting depth is the same. If the variable `lisp-indent-offset' is non-`nil', it overrides the usual indentation pattern for the second line of an expression, so that such lines are always indented `lisp-indent-offset' more columns than the containing list. The standard pattern is overridded for certain functions. Functions whose names start with `def' always indent the second line by `lisp-body-indention' extra columns beyond the open-parenthesis starting the expression. The standard pattern can be overridden in various ways for individual functions, according to the `lisp-indent-hook' property of the function name. There are four possibilities for this property: `nil' This is the same as no property; the standard indentation pattern is used. `defun' The pattern used for function names that start with `def' is used for this function also. a number, NUMBER The first NUMBER arguments of the function are "distinguished" arguments; the rest are considered the "body" of the expression. A line in the expression is indented according to whether the first argument on it is distinguished or not. If the argument is part of the body, the line is indented `lisp-body-indent' more columns than the open-parenthesis starting the containing expression. If the argument is distinguished and is either the first or second argument, it is indented twice that many extra columns. If the argument is distinguished and not the first or second argument, the standard pattern is followed for that line. a symbol, SYMBOL SYMBOL should be a function name; that function is called to calculate the indentation of a line within this expression. The function receives two arguments: STATE The value returned by `parse-partial-sexp' (a Lisp primitive for indentation and nesting computation) when it parses up to the beginning of this line. POS The position at which the line being indented begins. It should return either a number, which is the number of columns of indentation for that line, or a list whose car is such a number. The difference between returning a number and returning a list is that a number says that all following lines at the same nesting level should be indented just like this one; a list says that following lines might call for different indentations. This makes a difference when the indentation is being computed by `C-M-q'; if the value is a number, `C-M-q' need not recalculate indentation for the following lines until the end of the list. File: emacs Node: C Indent, Prev: Lisp Indent, Up: Grinding Customizing C Indentation ------------------------- Two variables control which commands perform C indentation and when. If `c-auto-newline' is non-`nil', newlines are inserted both before and after braces that you insert, and after colons and semicolons. Correct C indentation is done on all the lines that are made this way. If `c-tab-always-indent' is non-`nil', the TAB command in C mode does indentation only if point is at the left margin or within the line's indentation. If there is non-whitespace to the left of point, then TAB just inserts a tab character in the buffer. Normally, this variable is `nil', and TAB always reindents the current line. C does not have anything analogous to particular function names for which special forms of indentation are desirable. However, it has a different need for customization facilities: many different styles of C indentation are in common use. There are six variables you can set to control the style that Emacs C mode will use. `c-indent-level' Indentation of C statements within surrounding block. The surrounding block's indentation is the indentation of the line on which the open-brace appears. `c-continued-statement-offset' Extra indentation given to a substatement, such as the then-clause of an if or body of a while. `c-brace-offset' Extra indentation for line if it starts with an open brace. `c-brace-imaginary-offset' An open brace following other text is treated as if it were this far to the right of the start of its line. `c-argdecl-indent' Indentation level of declarations of C function arguments. `c-label-offset' Extra indentation for line that is a label, or case or default. The variable `c-indent-level' controls the indentation for C statements with respect to the surrounding block. In the example { foo (); the difference in indentation between the lines is `c-indent-level'. Its standard value is 2. If the open-brace beginning the compound statement is not at the beginning of its line, the `c-indent-level' is added to the indentation of the line, not the column of the open-brace. For example, if (losing) { do_this (); One popular indentation style is that which results from setting `c-indent-level' to 8 and putting open-braces at the end of a line in this way. I prefer to put the open-brace on a separate line. In fact, the value of the variable `c-brace-imaginary-offset' is also added to the indentation of such a statement. Normally this variable is zero. Think of this variable as the imaginary position of the open brace, relative to the first nonblank character on the line. By setting this variable to 4 and `c-indent-level' to 0, you can get this style: if (x == y) { do_it (); } When `c-indent-level' is zero, the statements inside most braces will line up right under the open brace. But there is an exception made for braces in column zero, such as surrounding a function's body. The statements just inside it do not go at column zero. Instead, `c-brace-offset' and `c-continued-statement-offset' (see below) are added to produce a typical offset between brace levels, and the statements are indented that far. `c-continued-statement-offset' controls the extra indentation for a line that starts within a statement (but not within parentheses or brackets). These lines are usually statements that are within other statements, such as the then-clauses of `if' statements and the bodies of `while' statements. This parameter is the difference in indentation between the two lines in if (x == y) do_it (); Its standard value is 2. Some popular indentation styles correspond to a value of zero for `c-continued-statement-offset'. `c-brace-offset' is the extra indentation given to a line that starts with an open-brace. Its standard value is zero; compare if (x == y) { with if (x == y) do_it (); if `c-brace-offset' were set to 4, the first example would become if (x == y) { `c-argdecl-indent' controls the indentation of declarations of the arguments of a C function. It is absolute: argument declarations receive exactly `c-argdecl-indent' spaces. The standard value is 5, resulting in code like this: char * index (string, char) char *string; int char; `c-label-offset' is the extra indentation given to a line that contains a label, a case statement, or a `default:' statement. Its standard value is -2, resulting in code like this switch (c) { case 'x': If `c-label-offset' were zero, the same code would be indented as switch (c) { case 'x': This example assumes that the other variables above also have their standard values. I strongly recommend that you try out the indentation style produced by the standard settings of these variables, together with putting open braces on separate lines. You can see how it looks in all the C source files of GNU Emacs. File: emacs Node: Matching, Prev: Grinding, Up: Programs, Next: Comments Automatic Display Of Matching Parentheses ========================================= The Emacs parenthesis-matching feature is designed to show automatically how parentheses match in the text. Whenever a self-inserting character that is a closing delimiter is typed, the cursor moves momentarily to the location of the matching opening delimiter, provided that is on the screen. If it is not on the screen, some text starting with that opening delimiter is displayed in the echo area. Either way, you can tell what grouping is being closed off. In Lisp, automatic matching applies only to parentheses. In C, it applies to braces and brackets too. Emacs knows which characters to regard as matching delimiters based on the syntax table, which is set by the major mode. *Note Syntax::. If the opening delimiter and closing delimiter are mismatched---such as in `[x)'---a warning message is displayed in the echo area. The correct matches are specified in the syntax table. Two variables control parenthesis match display. `blink-matching-paren' turns the feature on or off; `nil' turns it off, but the default is `t' to turn match display on. `blink-matching-paren-distance' specifies how many characters back to search to find the matching opening delimiter. If the match is not found in that far, scanning stops, and nothing is displayed. This is to prevent scanning for the matching delimiter from wasting lots of time when there is no match. The default is 4000. File: emacs Node: Comments, Prev: Matching, Up: Programs, Next: Balanced Editing Manipulating Comments ===================== The comment commands insert, kill and align comments. `M-;' Insert or align comment (`indent-for-comment'). `C-x ;' Set comment column (`set-comment-column'). `C-u - C-x ;' Kill comment on current line (`kill-comment'). `M-LFD' Like RET followed by inserting and aligning a comment (`indent-new-comment-line'). The command that creates a comment is `Meta-;' (`indent-for-comment'). If there is no comment already on the line, a new comment is created, aligned at a specific column called the "comment column". The comment is created by inserting the string Emacs thinks comments should start with (the value of `comment-start'; see below). Point is left after that string. If the text of the line extends past the comment column, then the indentation is done to a suitable boundary (usually, at least one space is inserted). If the major mode has specified a string to terminate comments, that is inserted after point, to keep the syntax valid. `Meta-;' can also be used to align an existing comment. If a line already contains the string that starts comments, then `M-;' just moves point after it and re-indents it to the conventional place. Exception: comments starting in column 0 are not moved. Some major modes have special rules for indenting certain kinds of comments in certain contexts. For example, in Lisp code, comments which start with two semicolons are indented as if they were lines of code, instead of at the comment column. Comments which start with three semicolons are supposed to start at the left margin. Emacs understands these conventions by indenting a double-semicolon comment using TAB, and by not changing the indentation of a triple-semicolon comment at all. ;; This function is just an example ;;; Here either two or three semicolons are appropriate. (defun foo (x) ;;; And now, the first part of the function: ;; The following line adds one. (1+ x)) ; This line adds one. In C code, a comment preceded on its line by nothing but whitespace is indented like a line of code. Even when an existing comment is properly aligned, `M-;' is still useful for moving directly to the start of the comment. `C-u - C-x ;' (`kill-comment') kills the comment on the current line, if there is one. The indentation before the start of the comment is killed as well. If there does not appear to be a comment in the line, nothing is done. To reinsert the comment on another line, move to the end of that line, do `C-y', and then do `M-;' to realign it. Note that `C-u - C-x ;' is not a distinct key; it is `C-x ;' (`set-comment-column') with a negative argument. That command is programmed so that when it receives a negative argument it calls `kill-comment'. However, `kill-comment' is a valid command which you could bind directly to a key if you wanted to. Multiple Lines of Comments -------------------------- If you are typing a comment and find that you wish to continue it on another line, you can use the command `Meta-LFD' (`indent-new-comment-line'), which terminates the comment you are typing, creates a new blank line afterward, and begins a new comment indented under the old one. When Auto Fill mode is on, going past the fill column while typing a comment causes the comment to be continued in just this fashion. If point is not at the end of the line when `M-LFD' is typed, the text on the rest of the line becomes part of the new comment line. Options Controlling Comments ---------------------------- The comment column is stored in the variable `comment-column'. You can set it to a number explicitly. Alternatively, the command `C-x ;' (`set-comment-column') sets the comment column to the column point is at. `C-u C-x ;' sets the comment column to match the last comment before point in the buffer, and then does a `Meta-;' to align the current line's comment under the previous one. Note that `C-u - C-x ;' runs the function `kill-comment' as described above. `comment-column' is a per-buffer variable; altering the variable affects only the current buffer, but there is a default value which you can change as well. *Note Locals::. Many major modes initialize this variable for the current buffer. The comment commands recognize comments based on the regular expression that is the value of the variable `comment-start-skip'. This regexp should not match the null string. It may match more than the comment starting delimiter in the strictest sense of the word; for example, in C mode the value of the variable is `"/\\*+ *"', which matches extra stars and spaces after the `/*' itself. (Note that `\\' is needed in Lisp syntax to include a `\' in the string, which is needed to deny the first star its special meaning in regexp syntax. *Note Regexps::.) When a comment command makes a new comment, it inserts the value of `comment-start' to begin it. The value of `comment-end' is inserted after point, so that it will follow the text that you will insert into the comment. In C mode, `comment-start' has the value `"/* "' and `comment-end' has the value `" */"'. `comment-multi-line' controls how `M-LFD' (`indent-new-comment-line') behaves when used inside a comment. If `comment-multi-line' is `nil', as it normally is, then the comment on the starting line is terminated and a new comment is started on the new following line. If `comment-multi-line' is not `nil', then the new following line is set up as part of the same comment that was found on the starting line. This is done by not inserting a terminator on the old line, and not inserting a starter on the new line. In languages where multi-line comments work, the choice of value for this variable is a matter of taste. The variable `comment-indent-hook' should contain a function that will be called to compute the indentation for a newly inserted comment or for aligning an existing comment. It is set differently by various major modes. The function is called with no arguments, but with point at the beginning of the comment, or at the end of a line if a new comment is to be inserted. It should return the column in which the comment ought to start. For example, in Lisp mode, the indent hook function bases its decision on how many semicolons begin an existing comment, and on the code in the preceding lines. File: emacs Node: Balanced Editing, Prev: Comments, Up: Programs, Next: Lisp Completion Editing Without Unbalanced Parentheses ====================================== `M-(' Put parentheses around next sexp(s) (`insert-parentheses'). `M-)' Move past next close parenthesis and re-indent (`move-over-close-and-reindent'). The commands `M-(' (`insert-parentheses') and `M-)' (`move-over-close-and-reindent') are designed to facilitate a style of editing which keeps parentheses balanced at all times. `M-(' inserts a pair of parentheses, either together as in `()', or, if given an argument, around the next several sexps, and leaves point after the open parenthesis. Instead of typing `( F O O )', you can type `M-( F O O', which has the same effect except for leaving the cursor before the close parenthesis. Then you would type `M-)', which moves past the close parenthesis, deleting any indentation preceding it (in this example there is none), and indenting with LFD after it. File: emacs Node: Lisp Completion, Prev: Balanced Editing, Up: Programs, Next: Documentation Completion for Lisp Symbols =========================== Usually completion happens in the minibuffer. But one kind of completion is available in all buffers: completion for Lisp symbol names. The command `M-TAB' (`lisp-complete-symbol') takes the partial Lisp symbol before point to be an abbreviation, and compares it against all nontrivial Lisp symbols currently known to Emacs. Any additional characters that they all have in common are inserted at point. Nontrivial symbols are those that have function definitions, values or properties. If there is an open-parenthesis immediately before the beginning of the partial symbol, only symbols with function definitions are considered as completions. If the partial name in the buffer has more than one possible completion and they have no additional characters in common, a list of all possible completions is displayed in another window. File: emacs Node: Documentation, Prev: Lisp Completion, Up: Programs, Next: Change Log Documentation Commands ====================== As you edit Lisp code to be run in Emacs, the commands `C-h f' (`describe-function') and `C-h v' (`describe-variable') can be used to print documentation of functions and variables that you want to call. These commands use the minibuffer to read the name of a function or variable to document, and display the documentation in a window. For extra convenience, these commands provide default arguments based on the code in the neighborhood of point. `C-h f' sets the default to the function called in the innermost list containing point. `C-h v' uses the symbol name around or adjacent to point as its default. Documentation on Unix commands, system calls and libraries can be obtained with the `M-x manual-entry' command. This reads a topic as an argument, and displays the text on that topic from the Unix manual. `manual-entry' always searches all 8 sections of the manual, and concatenates all the entries that are found. For example, the topic `termcap' finds the description of the termcap library from section 3, followed by the description of the termcap data base from section 5. File: emacs Node: Change Log, Prev: Documentation, Up: Programs, Next: Tags Change Logs =========== The Emacs command `M-x add-change-log-entry' helps you keep a record of when and why you have changed a program. It assumes that you have a file in which you write a chronological sequence of entries describing individual changes. The default is to store the change entries in a file called `ChangeLog' in the same directory as the file you are editing. The same `ChangeLog' file therefore records changes for all the files in the directory. A change log entry starts with a header line that contains your name and the current date. Aside from these header lines, every line in the change log starts with a tab. One entry can describe several changes; each change starts with a line starting with a tab and a star. `M-x add-change-log-entry' visits the change log file and creates a new entry unless the most recent entry is for today's date and your name. In either case, it adds a new line to start the description of another change just after the header line of the entry. When `M-x add-change-log-entry' is finished, all is prepared for you to edit in the description of what you changed and how. You must then save the change log file yourself. The change log file is always visited in Indented Text mode, which means that LFD and auto-filling indent each new line like the previous line. This is convenient for entering the contents of an entry, which must all be indented. *Note Text Mode::. Here is an example of the formatting conventions used in the change log for Emacs: Wed Jun 26 19:29:32 1985 Richard M. Stallman (rms at mit-prep) * xdisp.c (try_window_id): If C-k is done at end of next-to-last line, this fn updates window_end_vpos and cannot leave window_end_pos nonnegative (it is zero, in fact). If display is preempted before lines are output, this is inconsistent. Fix by setting blank_end_of_window to nonzero. Tue Jun 25 05:25:33 1985 Richard M. Stallman (rms at mit-prep) * cmds.c (Fnewline): Call the auto fill hook if appropriate. * xdisp.c (try_window_id): If point is found by compute_motion after xp, record that permanently. If display_text_line sets point position wrong (case where line is killed, point is at eob and that line is not displayed), set it again in final compute_motion. File: emacs Node: Tags, Prev: Change Log, Up: Programs, Next: Fortran Tag Tables ========== A "tag table" is a description of how a multi-file program is broken up into files. It lists the names of the component files and the names and positions of the functions in each file. Grouping the related files makes it possible to search or replace through all the files with one command. Recording the function names and positions makes possible the `Meta-.' command which you can use to find the definition of a function without having to know which of the files it is in. Tag tables are stored in files called "tag table files". The conventional name for a tag table file is `TAGS'. Each entry in the tag table records the name of one tag, the name of the file that the tag is defined in (implicitly), and the position in that file of the tag's definition. Just what names from the described files are recorded in the tag table depends on the programming language of the described file. They normally include all functions and subroutines, and may also include global variables, data types, and anything else convenient. In any case, each name recorded is called a "tag". * Menu: * Tag Syntax:: * Create Tag Table:: * Select Tag Table:: * Find Tag:: * Tags Search:: * Tags Stepping:: * List Tags:: File: emacs Node: Tag Syntax, Prev: Tags, Up: Tags, Next: Create Tag Table Source File Tag Syntax ---------------------- In Lisp code, any function defined with `defun', any variable defined with `defvar' or `defconst', and in general the first argument of any expression that starts with `(def' in column zero, is a tag. In C code, any C function is a tag, and so is any typedef if `-t' is specified when the tag table is constructed. In Fortran code, functions and subroutines are tags. In LaTeX text, the argument of any of the commands `\chapter', `\section', `\subsection', `\subsubsection', `\eqno', `\label', `\ref', `\cite', `\bibitem' and `\typeout' is a tag. File: emacs Node: Create Tag Table, Prev: Tag Syntax, Up: Tags, Next: Select Tag Table Creating Tag Tables ------------------- The `etags' program is used to create a tag table file. It knows the syntax of C, Fortran, LaTeX, Scheme and Emacs Lisp/Common Lisp. To use `etags', type etags INPUTFILES... as a shell command. It reads the specified files and writes a tag table named `TAGS' in the current working directory. `etags' recognizes the language used in an input file based on its file name and contents; there are no switches for specifying the language. The `-t' switch tells `etags' to record typedefs in C code as tags. If the tag table data become outdated due to changes in the files described in the table, the way to update the tag table is the same way it was made in the first place. It is not necessary to do this often. If the tag table fails to record a tag, or records it for the wrong file, then Emacs cannot possibly find its definition. However, if the position recorded in the tag table becomes a little bit wrong (due to some editing in the file that the tag definition is in), the only consequence is to slow down finding the tag slightly. Even if the stored position is very wrong, Emacs will still find the tag, but it must search the entire file for it. So you should update a tag table when you define new tags that you want to have listed, or when you move tag definitions from one file to another, or when changes become substantial. Normally there is no need to update the tag table after each edit, or even every day. File: emacs Node: Select Tag Table, Prev: Create Tag Table, Up: Tags, Next: Find Tag Selecting a Tag Table --------------------- Emacs has at any time one "selected" tag table, and all the commands for working with tag tables use the selected one. To select a tag table, type `M-x visit-tags-table', which reads the tag table file name as an argument. The name `TAGS' in the default directory is used as the default file name. All this command does is store the file name in the variable `tags-file-name'. Emacs does not actually read in the tag table contents until you try to use them. Setting this variable yourself is just as good as using `visit-tags-table'. The variable's initial value is `nil'; this value tells all the commands for working with tag tables that they must ask for a tag table file name to use. File: emacs Node: Find Tag, Prev: Select Tag Table, Up: Tags, Next: Tags Search Finding a Tag ------------- The most important thing that a tag table enables you to do is to find the definition of a specific tag. `M-. TAG' Find first definition of TAG (`find-tag'). `C-u M-.' Find next alternate definition of last tag specified. `C-x 4 . TAG' Find first definition of TAG, but display it in another window (`find-tag-other-window'). `M-.' (`find-tag') is the command to find the definition of a specified tag. It searches through the tag table for that tag, as a string, and then uses the tag table info to determine the file that the definition is in and the approximate character position in the file of the definition. Then `find-tag' visits that file, moves point to the approximate character position, and starts searching ever-increasing distances away for the the text that should appear at the beginning of the definition. If an empty argument is given (just type RET), the sexp in the buffer before or around point is used as the name of the tag to find. *Note Lists::, for info on sexps. The argument to `find-tag' need not be the whole tag name; it can be a substring of a tag name. However, there can be many tag names containing the substring you specify. Since `find-tag' works by searching the text of the tag table, it finds the first tag in the table that the specified substring appears in. The way to find other tags that match the substring is to give `find-tag' a numeric argument, as in `C-u M-.'; this does not read a tag name, but continues searching the tag table's text for another tag containing the same substring last used. If you have a real META key, `M-0 M-.' is an easier alternative to `C-u M-.'. Like most commands that can switch buffers, `find-tag' has another similar command that displays the new buffer in another window. `C-x 4 .' invokes the function `find-tag-other-window'. (This key sequence ends with a period.) Emacs comes with a tag table file `TAGS', in the directory containing Lisp libraries, which includes all the Lisp libraries and all the C sources of Emacs. By specifying this file with `visit-tags-table' and then using `M-.' you can quickly look at the source of any Emacs function. File: emacs Node: Tags Search, Prev: Find Tag, Up: Tags, Next: Tags Stepping Searching and Replacing with Tag Tables --------------------------------------- The commands in this section visit and search all the files listed in the selected tag table, one by one. For these commands, the tag table serves only to specify a sequence of files to search. A related command is `M-x grep' (*Note Compilation::). `M-x tags-search' Search for the specified regexp through the files in the selected tag table. `M-x tags-query-replace' Perform a `query-replace' on each file in the selected tag table. `M-,' Restart one of the commands above, from the current location of point (`tags-loop-continue'). `M-x tags-search' reads a regexp using the minibuffer, then visits the files of the selected tag table one by one, and searches through each one for that regexp. It displays the name of the file being searched so you can follow its progress. As soon as an occurrence is found, `tags-search' returns. Having found one match, you probably want to find all the rest. To find one more match, type `M-,' (`tags-loop-continue') to resume the `tags-search'. This searches the rest of the current buffer, followed by the remaining files of the tag table. `M-x tags-query-replace' performs a single `query-replace' through all the files in the tag table. It reads a string to search for and a string to replace with, just like ordinary `M-x query-replace'. It searches much like `M-x tags-search' but repeatedly, processing matches according to your input. *Note Replace::, for more information on `query-replace'. It is possible to get through all the files in the tag table with a single invocation of `M-x tags-query-replace'. But since any unrecognized character causes the command to exit, you may need to continue where you left off. `M-,' can be used for this. It resumes the last tags search or replace command that you did. It may have struck you that `tags-search' is a lot like `grep'. You can also run `grep' itself as an inferior of Emacs and have Emacs show you the matching lines one by one. This works mostly the same as running a compilation and having Emacs show you where the errors were. *Note Compilation::. File: emacs Node: Tags Stepping, Prev: Tags Search, Up: Tags, Next: List Tags Stepping Through a Tag Table ---------------------------- If you wish to process all the files in the selected tag table, but `M-x tags-search' and `M-x tags-query-replace' in particular are not what you want, you can use `M-x next-file'. `C-u M-x next-file' With a numeric argument, regardless of its value, visit the first file in the tag table, and prepare to advance sequentially by files. `M-x next-file' Visit the next file in the selected tag table. File: emacs Node: List Tags, Prev: Tags Stepping, Up: Tags Tag Table Inquiries ------------------- `M-x list-tags' Display a list of the tags defined in a specific program file. `M-x tags-apropos' Display a list of all tags matching a specified regexp. `M-x list-tags' reads the name of one of the files described by the selected tag table, and displays a list of all the tags defined in that file. The "file name" argument is really just a string to compare against the names recorded in the tag table; it is read as a string rather than as a file name. Therefore, completion and defaulting are not available, and you must enter the string the same way it appears in the tag table. Do not include a directory as part of the file name unless the file name recorded in the tag table includes a directory. `M-x tags-apropos' is like `apropos' for tags. It reads a regexp, then finds all the tags in the selected tag table whose entries match that regexp, and displays the tag names found. File: emacs Node: Fortran, Prev: Tags, Up: Programs Fortran Mode ============ Fortran mode provides special motion commands for Fortran statements and subprograms, and indentation commands that understand Fortran conventions of nesting, line numbers and continuation statements. Special commands for comments are provided because Fortran comments are unlike those of other languages. Built-in abbrevs optionally save typing when you insert Fortran keywords. Use `M-x fortran-mode' to switch to this major mode. Doing so calls the value of `fortran-mode-hook' as a function of no arguments if that variable has a value that is not `nil'. * Menu: * Motion: Fortran Motion. Moving point by statements or subprograms. * Indent: Fortran Indent. Indentation commands for Fortran. * Comments: Fortran Comments. Inserting and aligning comments. * Columns: Fortran Columns. Measuring columns for valid Fortran. * Abbrev: Fortran Abbrev. Built-in abbrevs for Fortran keywords. Fortran mode was contributed by Michael Prange. File: emacs Node: Fortran Motion, Prev: Fortran, Up: Fortran, Next: Fortran Indent Motion Commands --------------- Fortran mode provides special commands to move by subprograms (functions and subroutines) and by statements. There is also a command to put the region around one subprogram, convenient for killing it or moving it. `C-M-a' Move to beginning of subprogram (`beginning-of-fortran-subprogram'). `C-M-e' Move to end of subprogram (`end-of-fortran-subprogram'). `C-M-h' Put point at beginning of subprogram and mark at end (`mark-fortran-subprogram'). `C-c C-n' Move to beginning of current or next statement (`fortran-next-statement'). `C-c C-p' Move to beginning of current or previous statement (`fortran-previous-statement'). File: emacs Node: Fortran Indent, Prev: Fortran Motion, Up: Fortran, Next: Fortran Comments Fortran Indentation ------------------- Special commands and features are needed for indenting Fortran code in order to make sure various syntactic entities (line numbers, comment line indicators and continuation line flags) appear in the columns that are required for standard Fortran. * Menu: * Commands: ForIndent Commands. Commands for indenting Fortran. * Numbers: ForIndent Num. How line numbers auto-indent. * Conv: ForIndent Conv. Conventions you must obey to avoid trouble. * Vars: ForIndent Vars. Variables controlling Fortran indent style. File: emacs Node: ForIndent Commands, Prev: Fortran Indent, Up: Fortran Indent, Next: ForIndent Num Fortran Indentation Commands ............................ `TAB' Indent the current line (`fortran-indent-line'). `M-LFD' Break the current line and set up a continuation line. `C-M-q' Indent all the lines of the subprogram point is in (`fortran-indent-subprogram'). TAB is redefined by Fortran mode to reindent the current line for Fortran (`fortran-indent-line'). Line numbers and continuation markers are indented to their required columns, and the body of the statement is independently indented based on its nesting in the program. The key `C-M-q' is redefined as `fortran-indent-subprogram', a command to reindent all the lines of the Fortran subprogram (function or subroutine) containing point. The key `M-LFD' is redefined as `fortran-split-line', a command to split a line in the appropriate fashion for Fortran. In a non-comment line, the second half becomes a continuation line and is indented accordingly. In a comment line, both halves become separate comment lines. File: emacs Node: ForIndent Num, Prev: ForIndent Commands, Up: Fortran Indent, Next: ForIndent Conv Line Numbers and Continuation ............................. If a number is the first non-whitespace in the line, it is assumed to be a line number and is moved to columns 0 through 4. (Columns are always counted from 0 in GNU Emacs.) If the text on the line starts with the conventional Fortran continuation marker `$', it is moved to column 5. If the text begins with any non whitespace character in column 5, it is assumed to be an unconventional continuation marker and remains in column 5. Line numbers of four digits or less are normally indented one space. This amount is controlled by the variable `fortran-line-number-indent' which is the maximum indentation a line number can have. Line numbers are indented to right-justify them to end in column 4 unless that would require more than this maximum indentation. The default value of the variable is 1. Simply inserting a line number is enough to indent it according to these rules. As each digit is inserted, the indentation is recomputed. To turn off this feature, set the variable `fortran-electric-line-number' to `nil'. Then inserting line numbers is like inserting anything else. File: emacs Node: ForIndent Conv, Prev: ForIndent Num, Up: Fortran Indent, Next: ForIndent Vars Syntactic Conventions ..................... Fortran mode assumes that you follow certain conventions that simplify the task of understanding a Fortran program well enough to indent it properly: * Two nested `do' loops never share a `continue' statement. * The same character appears in column 5 of all continuation lines, and this character is the value of the variable `fortran-continuation-char'. By default, this character is `$'. If you fail to follow these conventions, the indentation commands may indent some lines unaesthetically. However, a correct Fortran program will retain its meaning when reindented even if the conventions are not followed. File: emacs Node: ForIndent Vars, Prev: ForIndent Conv, Up: Fortran Indent Variables for Fortran Indentation ................................. Several additional variables control how Fortran indentation works. `fortran-do-indent' Extra indentation within each level of `do' statement (default 3). `fortran-if-indent' Extra indentation within each level of `if' statement (default 3). `fortran-continuation-indent' Extra indentation for bodies of continuation lines (default 5). `fortran-check-all-num-for-matching-do' If this is `nil', indentation assumes that each `do' statement ends on a `continue' statement. Therefore, when computing indentation for a statement other than `continue', it can save time by not checking for a `do' statement ending there. If this is non-`nil', indenting any numbered statement must check for a `do' that ends there. The default is `nil'. `fortran-minimum-statement-indent' Minimum indentation for fortran statements. For standard Fortran, this is 6. Statement bodies will never be indented less than this much. File: emacs Node: Fortran Comments, Prev: Fortran Indent, Up: Fortran, Next: Fortran Columns Comments -------- The usual Emacs comment commands assume that a comment can follow a line of code. In Fortran, the standard comment syntax requires an entire line to be just a comment. Therefore, Fortran mode replaces the standard Emacs comment commands and defines some new variables. Fortran mode can also handle a nonstandard comment syntax where comments start with `!' and can follow other text. Because only some Fortran compilers accept this syntax, Fortran mode will not insert such comments unless you have said in advance to do so. To do this, set the variable `comment-start' to `"!"' (*Note Variables::). `M-;' Align comment or insert new comment (`fortran-comment-indent'). `C-x ;' Applies to nonstandard `!' comments only. `C-c ;' Turn all lines of the region into comments, or (with arg) turn them back into real code (`fortran-comment-region'). `M-;' in Fortran mode is redefined as the command `fortran-comment-indent'. Like the usual `M-;' command, this recognizes any kind of existing comment and aligns its text appropriately; if there is no existing comment, a comment is inserted and aligned. But inserting and aligning comments are not the same in Fortran mode as in other modes. When a new comment must be inserted, if the current line is blank, a full-line comment is inserted. On a non-blank line, a nonstandard `!' comment is inserted if you have said you want to use them. Otherwise a full-line comment is inserted on a new line before the current line. Nonstandard `!' comments are aligned like comments in other languages, but full-line comments are different. In a standard full-line comment, the comment delimiter itself must always appear in column zero. What can be aligned is the text within the comment. You can choose from three styles of alignment by setting the variable `fortran-comment-indent-style' to one of these values: `fixed' The text is aligned at a fixed column, which is the value of `fortran-comment-line-column'. This is the default. `relative' The text is aligned as if it were a line of code, but with an additional `fortran-comment-line-column' columns of indentation. `nil' Text in full-line columns is not moved automatically. In addition, you can specify the character to be used to indent within full-line comments by setting the variable `fortran-comment-indent-char' to the character you want to use. Fortran mode introduces two variables `comment-line-start' and `comment-line-start-skip' which play for full-line comments the same roles played by `comment-start' and `comment-start-skip' for ordinary text-following comments. Normally these are set properly by Fortran mode so you do not need to change them. The normal Emacs comment command `C-x ;' has not been redefined. If you use `!' comments, this command can be used with them. Otherwise it is useless in Fortran mode. The command `C-c ;' (`fortran-comment-region') turns all the lines of the region into comments by inserting the string `C$$$' at the front of each one. With a numeric arg, the region is turned back into live code by deleting `C$$$' from the front of each line in it. The string used for these comments can be controlled by setting the variable `fortran-comment-region'. Note that here we have an example of a command and a variable with the same name; these two uses of the name never conflict because in Lisp and in Emacs it is always clear from the context which one is meant.