This is Info file ../info/emacs, produced by Makeinfo-1.55 from the input file emacs.texi.  File: emacs, Node: Symbol Completion, Next: Documentation, Prev: Balanced Editing, Up: Programs Completion for Symbol Names =========================== Usually completion happens in the minibuffer. But one kind of completion is available in all buffers: completion for symbol names. The character `M-TAB' runs a command to complete the partial symbol before point against the set of meaningful symbol names. Any additional characters determined by the partial name are inserted at point. 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. There are two ways of determining the set of legitimate symbol names to complete against. In most major modes, this uses a tags table (*note Tags::.); the legitimate symbol names are the tag names listed in the tags table file. The command which implements this is `complete-tag'. In Emacs-Lisp mode, the name space for completion normally consists of nontrivial symbols present in Emacs--those that have function definitions, values or properties. However, if there is an open-parenthesis immediately before the beginning of the partial symbol, only symbols with function definitions are considered as completions. The command which implements this is `lisp-complete-symbol'. In Text mode and related modes, `M-TAB' completes words based on the spell-checker's dictionary. *Note Spelling::.  File: emacs, Node: Documentation, Next: Change Log, Prev: Symbol Completion, Up: Programs 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 operating system commands, library functions and system calls can be obtained with the `M-x manual-entry' command. This reads a topic as an argument, and displays the "man page" on that topic. `manual-entry' starts a background process that formats the manual page, by running the `man' program. The result goes in a buffer named `*man TOPIC*'. These buffers use a special major mode, Man mode, that facilitates scrolling and examining other manual pages. For details, type `C-h m' while in a man page buffer. For a long man page, setting the faces properly can take substantial time. By default, Emacs uses faces in man pages if you are using X Windows. You can turn off use of faces in man pages by setting the variable `Man-fontify-manpage-flag' to `nil'. If you insert the text of a man page into an Emacs buffer in some other fashion, you can use the command `M-x Man-fontify-manpage' to perform the same conversions that `M-x manual-entry' does. Eventually the GNU project hopes to replace most man pages with better-organized manuals that you can browse with Info. *Note Misc Help::. Since this process is only partially completed, it is still useful to read manual pages.  File: emacs, Node: Change Log, Next: Tags, Prev: Documentation, Up: Programs Change Logs =========== The Emacs command `C-x 4 a' adds a new entry to the change log file for the file you are editing (`add-change-log-entry-other-window'). A change log file contains a chronological record of when and why you have changed a program, consisting of a sequence of entries describing individual changes. Normally it is kept in a file called `ChangeLog' in the same directory as the file you are editing, or one of its parent directories. A single `ChangeLog' file can record changes for all the files in its directory and all its subdirectories. A change log entry starts with a header line that contains your name, your email address (taken from the variable `user-mail-address'), and the current date and time. Aside from these header lines, every line in the change log starts with a space or a tab. The bulk of the entry consists of "items", each of which starts with a line starting with whitespace and a star. Here are two entries, each with two items: Wed May 5 14:11:45 1993 Richard Stallman * man.el: Rename symbols `man-*' to `Man-*'. (manual-entry): Make prompt string clearer. * simple.el (blink-matching-paren-distance): Change default to 12,000. Tue May 4 12:42:19 1993 Richard Stallman * vc.el (minor-mode-map-alist): Don't use it if it's void. (vc-cancel-version): Doc fix. One entry can describe several changes; each change should have its own item. Normally there should be a blank line between items. When items are related (parts of the same change, in different places), group them by leaving no blank line between them. The second entry above contains two items grouped in this way. `C-x 4 a' visits the change log file and creates a new entry unless the most recent entry is for today's date and your name. It also creates a new item for the current file. For many languages, it can even guess the name of the function or other object that was changed. The change log file is visited in Change Log mode. In this major mode, each bunch of grouped items counts as one paragraph, and each entry is considered a page. This facilitates editing the entries. LFD and auto-fill indent each new line like the previous line; this is convenient for entering the contents of an entry. Version control systems are another way keep track of changes in your program and keep a change log. *Note Log Entries::.  File: emacs, Node: Tags, Next: Emerge, Prev: Change Log, Up: Programs Tags Tables =========== A "tags 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 (or other named subunits) 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 `M-.' command which finds the definition of a function by looking up which of the files it is in. Tags tables are stored in files called "tags table files". The conventional name for a tags table file is `TAGS'. Each entry in the tags 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 tags 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. Each name recorded is called a "tag". * Menu: * Tag Syntax:: Tag syntax for various types of code and text files. * Create Tags Table:: Creating a tags table with `etags'. * Select Tags Table:: How to visit a tags table. * Find Tag:: Commands to find the definition of a specific tag. * Tags Search:: Using a tags table for searching and replacing. * Tags Stepping:: Visiting files in a tags table, one by one. * List Tags:: Listing and finding tags defined in a file.  File: emacs, Node: Tag Syntax, Next: Create Tags Table, Up: Tags 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 Scheme code, tags include anything defined with `def' or with a construct whose name starts with `def'. They also include variables set with `set!' at top level in the file. * In C code, any C function or typedef is a tag, and so are definitions of struct, union and enum. Any `#define' is also a tag, unless `--no-defines' is specified when the tags table is constructed, which sometimes makes the tags file much smaller. In C++ code, member functions are also recognized. * In Yacc or Bison input files, each rule defines as a tag the nonterminal it constructs. The portions of the file that contain C code are parsed as C code. * In Fortran code, functions and subroutines are tags. * In Pascal code, the tags are the functions and procedures defined in the file. * In Perl code, the tags are the procedures defined by the `sub' keyword. * In Prolog code, a tag name appears at the left margin. * In assembler code, labels appearing at the beginning of a line, followed by a colon, are tags. * In LaTeX text, the argument of any of the commands `\chapter', `\section', `\subsection', `\subsubsection', `\eqno', `\label', `\ref', `\cite', `\bibitem', `\part', `\appendix', `\entry', or `\index', is a tag. Other commands can make tags as well, if you specify them in the environment variable `TEXTAGS' before invoking `etags'. The value of this environment variable should be a colon-separated list of commands names. For example, TEXTAGS="def:newcommand:newenvironment" export TEXTAGS specifies (using Bourne shell syntax) that the commands `\def', `\newcommand' and `\newenvironment' also define tags. * You can also generate tags based on regexp matching (*note Create Tags Table::.) for any text file.  File: emacs, Node: Create Tags Table, Next: Select Tags Table, Prev: Tag Syntax, Up: Tags Creating Tags Tables -------------------- The `etags' program is used to create a tags table file. It knows the syntax of several languages, as described in *Note Tag Syntax::. Here is how to run `etags': etags INPUTFILES... The `etags' program reads the specified files, and writes a tags table named `TAGS' in the current working directory. `etags' recognizes the language used in an input file based on its file name and contents. You can specify the language with the `--language=NAME' option, described below. If the tags table data become outdated due to changes in the files described in the table, the way to update the tags table is the same way it was made in the first place. It is not necessary to do this often. If the tags 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 tags table becomes a little bit wrong (due to some editing in the file that the tag definition is in), the only consequence is a slight delay in finding the tag. 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 tags 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 tags table after each edit, or even every day. One tags table can effectively include another. Specify the included tags file name with the `--include=FILE' option when creating the file that is to include it. The latter file then acts as if it contained all the files specified in the included file, as well as the files it directly contains. When you want to make a tags table from a great number of files, you may have problems listing them on the command line, because some systems have a limit on its length. The simplest way to circumvent this limit is to tell `etags' to read the file names from its standard input, by typing a dash in place of the file names, like this: find . -name "*.[chCH]" -print | etags - Use the option `--language=NAME' to specify the language explicitly. You can intermix these options with file names; each one applies to the file names that follow it. Specify `--language=auto' to tell `etags' to resume guessing the language from the file names and file contents. Specify `--language=none' to turn off language-specific processing entirely; then `etags' recognizes tags by regexp matching alone. `etags --help' prints the list of the languages `etags' knows, and the file name rules for guessing the language. The `--regex' option provides a general way of recognizing tags based on regexp matching. You can freely intermix it with file names. Each `--regex' option adds to the preceding ones, and applies only to the following files. The syntax is: --regex=/TAGREGEXP[/NAMEREGEXP]/ where TAGREGEXP is used to match the lines to tag. It is always anchored, that is, it behaves as if preceded by `^'. If you want to account for indentation, just match any initial number of blanks by beginning your regular expression with `[ \t]*'. In the regular expressions, `\' quotes the next character, and `\t' stands for the tab character. Note that `etags' does not handle the other C escape sequences for special characters. You should not match more characters with TAGREGEXP than that needed to recognize what you want to tag. If the match is such that more characters than needed are unavoidably matched by TAGREGEXP, you may find useful to add a NAMEREGEXP, in order to narrow the tag scope. You can find some examples below. The `-R' option deletes all the regexps defined with `--regex' options. It applies to the file names following it, as you can see from the following example: etags --regex=/REG1/ voo.doo --regex=/REG2/ \ bar.ber -R --lang=lisp los.er Here `etags' chooses the parsing language for `voo.doo' and `bar.ber' according to their contents. `etags' also uses REG1 to recognize additional tags in `voo.doo', and both REG1 and REG2 to recognize additional tags in `bar.ber'. `etags' uses the Lisp tags rules, and no regexp matching, to recognize tags in `los.er'. Here are some more examples. The regexps are quoted to protect them from shell interpretation. Tag the `DEFVAR' macros in the emacs source files: --regex='/[ \t]*DEFVAR_[A-Z_ \t(]+"\([^"]+\)"/' Tag VHDL files (this example is a single long line, broken here for formatting reasons): --language=none --regex='/[ \t]*\(ARCHITECTURE\|CONFIGURATION\) +[^ ]* +OF/' --regex='/[ \t]*\(ATTRIBUTE\|ENTITY\|FUNCTION\|PACKAGE\ \( BODY\)?\|PROCEDURE\|PROCESS\|TYPE\)[ \t]+\([^ \t(]+\)/\3/' Tag Cobol files (every label starting in column seven): --language=none --regex='/.......[a-zA-Z0-9-]+\./' Tag Postscript files (every label starting in column one): --language=none --regex='#/[^ \t{]+#/' Tag TCL files (this last example shows the usage of a NAMEREGEXP): --lang=none --regex='/proc[ \t]+\([^ \t]+\)/\1/' For a list of the other available `etags' options, execute `etags --help'.  File: emacs, Node: Select Tags Table, Next: Find Tag, Prev: Create Tags Table, Up: Tags Selecting a Tags Table ---------------------- Emacs has at any time one "selected" tags table, and all the commands for working with tags tables use the selected one. To select a tags table, type `M-x visit-tags-table', which reads the tags 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 tags 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'; that value tells all the commands for working with tags tables that they must ask for a tags table file name to use. Using `visit-tags-table' when a tags table is already loaded gives you a choice: you can add the new tags table to the current list of tags tables, or start a new list. The tags commands use all the tags tables in the current list. If you start a new list, the new tags table is used *instead* of others. If you add the new table to the current list, it is used *as well as* the others. When the tags commands scan the list of tags tables, they don't always start at the beginning of the list; they start with the first tags table (if any) that describes the current file, proceed from there to the end of the list, and then scan from the beginning of the list until they have covered all the tables in the list. You can specify a precise list of tags tables by setting the variable `tags-table-list' to a list of strings, like this: (setq tags-table-list '("~/emacs" "/usr/local/lib/emacs/src")) This tells the tags commands to look at the `TAGS' files in your `~/emacs' directory and in the `/usr/local/lib/emacs/src' directory. The order depends on which file you are in and which tags table mentions that file, as explained above. Do not set both `tags-file-name' and `tags-table-list'.  File: emacs, Node: Find Tag, Next: Tags Search, Prev: Select Tags Table, Up: Tags Finding a Tag ------------- The most important thing that a tags table enables you to do is to find the definition of a specific tag. `M-. TAG RET' Find first definition of TAG (`find-tag'). `C-u M-.' Find next alternate definition of last tag specified. `C-u - M-.' Go back to previous tag found. `C-M-. PATTERN RET' Find a tag whose name matches PATTERN (`find-tag-regexp'). `C-u C-M-.' Find the next tag whose name matches the last pattern used. `C-x 4 . TAG RET' Find first definition of TAG, but display it in another window (`find-tag-other-window'). `C-x 5 . TAG RET' Find first definition of TAG, and create a new frame to select the buffer (`find-tag-other-frame'). `M-.' (`find-tag') is the command to find the definition of a specified tag. It searches through the tags table for that tag, as a string, and then uses the tags 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 searches ever-increasing distances away to find the tag definition. If an empty argument is given (just type RET), the sexp in the buffer before or around point is used as the TAG argument. *Note Lists::, for info on sexps. You don't need to give `M-.' the full name of the tag; a part will do. This is because `M-.' finds tags in the table which contain TAG as a substring. However, it prefers an exact match to a substring match. To find other tags that match the same substring, give `find-tag' a numeric argument, as in `C-u M-.'; this does not read a tag name, but continues searching the tags 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 a variant that displays the new buffer in another window, and one that makes a new frame for it. The former is `C-x 4 .', which invokes the command `find-tag-other-window'. The latter is `C-x 5 .', which invokes `find-tag-other-frame'. To move back to places you've found tags recently, use `C-u - M-.'; more generally, `M-.' with a negative numeric argument. This command can take you to another buffer. `C-x 4 .' with a negative argument finds the previous tag location in another window. The command `C-M-.' (`find-tag-regexp') visits the tags that match a specified regular expression. It is just like `M-.' except that it does regexp matching instead of substring matching.  File: emacs, Node: Tags Search, Next: Tags Stepping, Prev: Find Tag, Up: Tags Searching and Replacing with Tags Tables ---------------------------------------- The commands in this section visit and search all the files listed in the selected tags table, one by one. For these commands, the tags table serves only to specify a sequence of files to search. `M-x tags-search RET REGEXP RET' Search for REGEXP through the files in the selected tags table. `M-x tags-query-replace RET REGEXP RET REPLACEMENT RET' Perform a `query-replace-regexp' on each file in the selected tags 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 searches for matches in all the files in the selected tags table, one file at a time. It displays the name of the file being searched so you can follow its progress. As soon as it finds an occurrence, `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 tags table. `M-x tags-query-replace' performs a single `query-replace-regexp' through all the files in the tags table. It reads a regexp to search for and a string to replace with, just like ordinary `M-x query-replace-regexp'. 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 tags table with a single invocation of `M-x tags-query-replace'. But often it is useful to exit temporarily, which you can do with any input event that has no special query replace meaning. You can resume the query replace subsequently by typing `M-,'; this command resumes the last tags search or replace command that you did. The commands in this section carry out much broader searches than the `find-tag' family. The `find-tag' commands search only for definitions of tags that match your substring or regexp. The commands `tags-search' and `tags-query-replace' find every occurrence of the regexp, as ordinary search commands and replace commands do in the current buffer. These commands create buffers only temporarily for the files that they have to search (those which are not already visited in Emacs buffers). Buffers in which no match is found are quickly killed; the others continue to exist. 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 much like running a compilation; finding the source locations of the `grep' matches works like finding the compilation errors. *Note Compilation::.  File: emacs, Node: Tags Stepping, Next: List Tags, Prev: Tags Search, Up: Tags Stepping Through a Tags Table ----------------------------- If you wish to process all the files in the selected tags table, but not in the specific ways that `M-x tags-search' and `M-x tags-query-replace' do, you can use `M-x next-file' to visit the files one by one. `C-u M-x next-file' Visit the first file in the tags table, and prepare to advance sequentially by files. `M-x next-file' Visit the next file in the selected tags table.  File: emacs, Node: List Tags, Prev: Tags Stepping, Up: Tags Tags Table Inquiries -------------------- `M-x list-tags RET FILE RET' Display a list of the tags defined in the program file `file'. `M-x tags-apropos RET REGEXP RET' Display a list of all tags matching REGEXP. `M-x list-tags' reads the name of one of the files described by the selected tags 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 file names recorded in the tags 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 file name the same way it appears in the tags table. Do not include a directory as part of the file name unless the file name recorded in the tags table includes a directory. `M-x tags-apropos' is like `apropos' for tags (*note Apropos::.). It reads a regexp, then finds all the tags in the selected tags table whose entries match that regexp, and displays the tag names found. You can also perform completion in the buffer on the name space of tag names in the current tags tables. *Note Symbol Completion::.  File: emacs, Node: Emerge, Next: C Mode, Prev: Tags, Up: Programs Merging Files with Emerge ========================= It's not unusual for programmers to get their signals crossed and modify the same program in two different directions. To recover from this confusion, you need to merge the two versions. Emerge makes this easier. See also *Note Comparing Files::. * Menu: * Overview of Emerge:: How to start Emerge. Basic concepts. * Submodes of Emerge:: Fast mode vs. Edit mode. Skip Prefers mode and Auto Advance mode. * State of Difference:: You do the merge by specifying state A or B for each difference. * Merge Commands:: Commands for selecting a difference, changing states of differences, etc. * Exiting Emerge:: What to do when you've finished the merge. * Combining in Emerge:: How to keep both alternatives for a difference. * Fine Points of Emerge:: Misc.  File: emacs, Node: Overview of Emerge, Next: Submodes of Emerge, Up: Emerge Overview of Emerge ------------------ To start Emerge, run one of these four commands: `M-x emerge-files' Merge two specified files. `M-x emerge-files-with-ancestor' Merge two specified files, with reference to a common ancestor. `M-x emerge-buffers' Merge two buffers. `M-x emerge-buffers-with-ancestor' Merge two buffers with reference to a common ancestor in a third buffer. The Emerge commands compare two files or buffers, and display the comparison in three buffers: one for each input text (the "A buffer" and the "B buffer"), and one (the "merge buffer") where merging takes place. The merge buffer shows the full merged text, not just the differences. Wherever the two input texts differ, you can choose which one of them to include in the merge buffer. The Emerge commands that take input from existing buffers use only the accessible portions of those buffers, if they are narrowed (*note Narrowing::.). If a common ancestor version is available, from which the two texts to be merged were both derived, Emerge can use it to guess which alternative is right. Wherever one current version agrees with the ancestor, Emerge presumes that the other current version is a deliberate change which should be kept in the merged version. Use the `with-ancestor' commands if you want to specify a common ancestor text. These commands read three file or buffer names--variant A, variant B, and the common ancestor. After the comparison is done and the buffers are prepared, the interactive merging starts. You control the merging by typing special "merge commands" in the merge buffer. The merge buffer shows you a full merged text, not just differences. For each run of differences between the input texts, you can choose which one of them to keep, or edit them both together. The merge buffer uses a special major mode, Emerge mode, with commands for making these choices. But you can also edit the buffer with ordinary Emacs commands. At any given time, the attention of Emerge is focused on one particular difference, called the "selected" difference. This difference is marked off in the three buffers like this: vvvvvvvvvvvvvvvvvvvv TEXT THAT DIFFERS ^^^^^^^^^^^^^^^^^^^^ Emerge numbers all the differences sequentially and the mode line always shows the number of the selected difference. Normally, the merge buffer starts out with the A version of the text. But when the A version of a difference agrees with the common ancestor, then the B version is initially preferred for that difference. Emerge leaves the merged text in the merge buffer when you exit. At that point, you can save it in a file with `C-x C-w'. If you give a numeric argument to `emerge-files' or `emerge-files-with-ancestor', it reads the name of the output file using the minibuffer. (This is the last file name those commands read.) Then exiting from Emerge saves the merged text in the output file. Normally, Emerge commands save the output buffer in its file when you exit. If you abort Emerge with `C-]', the Emerge command does not save the output buffer, but you can save it yourself if you wish.  File: emacs, Node: Submodes of Emerge, Next: State of Difference, Prev: Overview of Emerge, Up: Emerge Submodes of Emerge ------------------ You can choose between two modes for giving merge commands: Fast mode and Edit mode. In Fast mode, basic merge commands are single characters, but ordinary Emacs commands are disabled. This is convenient if you use only merge commands. In Edit mode, all merge commands start with the prefix key `C-c C-c', and the normal Emacs commands are also available. This allows editing the merge buffer, but slows down Emerge operations. Use `e' to switch to Edit mode, and `C-c C-c f' to switch to Fast mode. The mode line indicates Edit and Fast modes with `E' and `F'. Emerge has two additional submodes that affect how particular merge commands work: Auto Advance mode and Skip Prefers mode. If Auto Advance mode is in effect, the `a' and `b' commands advance to the next difference. This lets you go through the merge faster as long as you simply choose one of the alternatives from the input. The mode line indicates Auto Advance mode with `A'. If Skip Prefers mode is in effect, the `n' and `p' commands skip over differences in states prefer-A and prefer-B (*note State of Difference::.). Thus you see only differences for which neither version is presumed "correct". The mode line indicates Skip Prefers mode with `S'. Use the command `s a' (`emerge-auto-advance-mode') to set or clear Auto Advance mode. Use `s s' (`emerge-skip-prefers-mode') to set or clear Skip Prefers mode. These commands turn on the mode with a positive argument, turns it off with a negative or zero argument, and toggle the mode with no argument.  File: emacs, Node: State of Difference, Next: Merge Commands, Prev: Submodes of Emerge, Up: Emerge State of a Difference --------------------- In the merge buffer, a difference is marked with lines of `v' and `^' characters. Each difference has one of these seven states: A The difference is showing the A version. The `a' command always produces this state; the mode line indicates it with `A'. B The difference is showing the B version. The `b' command always produces this state; the mode line indicates it with `B'. default-A default-B The difference is showing the A or the B state by default, because you haven't made a choice. All differences start in the default-A state (and thus the merge buffer is a copy of the A buffer), except those for which one alternative is "preferred" (see below). When you select a difference, its state changes from default-A or default-B to plain A or B. Thus, the selected difference never has state default-A or default-B, and these states are never displayed in the mode line. The command `d a' chooses default-A as the default state, and `d b' chooses default-B. This chosen default applies to all differences which you haven't ever selected and for which no alternative is preferred. If you are moving through the merge sequentially, the differences you haven't selected are those following the selected one. Thus, while moving sequentially, you can effectively make the A version the default for some sections of the merge buffer and the B version the default for others by using `d a' and `d b' between sections. prefer-A prefer-B The difference is showing the A or B state because it is "preferred". This means that you haven't made an explicit choice, but one alternative seems likely to be right because the other alternative agrees with the common ancestor. Thus, where the A buffer agrees with the common ancestor, the B version is preferred, because chances are it is the one that was actually changed. These two states are displayed in the mode line as `A*' and `B*'. combined The difference is showing a combination of the A and B states, as a result of the `x c' or `x C' commands. Once a difference is in this state, the `a' and `b' commands don't do anything to it unless you give them a numeric argument. The mode line displays this state as `comb'.  File: emacs, Node: Merge Commands, Next: Exiting Emerge, Prev: State of Difference, Up: Emerge Merge Commands -------------- Here are the Merge commands for Fast mode; in Edit mode, precede them with `C-c C-c': `p' Select the previous difference. `n' Select the next difference. `a' Choose the A version of this difference. `b' Choose the B version of this difference. `C-u N j' Select difference number N. `.' Select the difference containing point. You can use this command in the merge buffer or in the A or B buffer. `q' Quit--finish the merge. `C-]' Abort--exit merging and do not save the output. `f' Go into Fast mode. (In Edit mode, this is actually `C-c C-c f'.) `e' Go into Edit mode. `l' Recenter (like `C-l') all three windows. `-' Specify part of a prefix numeric argument. `DIGIT' Also specify part of a prefix numeric argument. `d a' Choose the A version as the default from here down in the merge buffer. `d b' Choose the B version as the default from here down in the merge buffer. `c a' Copy the A version of this difference into the kill ring. `c b' Copy the B version of this difference into the kill ring. `i a' Insert the A version of this difference at point. `i b' Insert the B version of this difference at point. `m' Put point and mark around the difference. `^' Scroll all three windows down (like `M-v'). `v' Scroll all three windows up (like `C-v'). `<' Scroll all three windows left (like `C-x <'). `>' Scroll all three windows right (like `C-x >'). `|' Reset horizontal scroll on all three windows. `x 1' Shrink the merge window to one line. (Use `C-u l' to restore it to full size.) `x c' Combine the two versions of this difference (*note Combining in Emerge::.). `x f' Show the names of the files/buffers Emerge is operating on, in a Help window. (Use `C-u l' to restore windows.) `x j' Join this difference with the following one. (`C-u x j' joins this difference with the previous one.) `x s' Split this difference into two differences. Before you use this command, position point in each of the three buffers at the place where you want to split the difference. `x t' Trim identical lines off top and bottom of the difference. Such lines occur when the A and B versions are identical but differ from the ancestor version.  File: emacs, Node: Exiting Emerge, Next: Combining in Emerge, Prev: Merge Commands, Up: Emerge Exiting Emerge -------------- The `q' command (`emerge-quit') finishes the merge, storing the results into the output file if you specified one. It restores the A and B buffers to their proper contents, or kills them if they were created by Emerge and you haven't changed them. It also disables the Emerge commands in the merge buffer, since executing them later could damage the contents of the various buffers. `C-]' aborts the merge. This means exiting without writing the output file. If you didn't specify an output file, then there is no real difference between aborting and finishing the merge. If the Emerge command was called from another Lisp program, then its return value is `t' for successful completion, or `nil' if you abort.  File: emacs, Node: Combining in Emerge, Next: Fine Points of Emerge, Prev: Exiting Emerge, Up: Emerge Combining the Two Versions -------------------------- Sometimes you want to keep *both* alternatives for a particular difference. To do this, use `x c', which edits the merge buffer like this: #ifdef NEW VERSION FROM A BUFFER #else /* NEW */ VERSION FROM B BUFFER #endif /* NEW */ While this example shows C preprocessor conditionals delimiting the two alternative versions, you can specify the strings to use by setting the variable `emerge-combine-versions-template' to a string of your choice. In the string, `%a' says where to put version A, and `%b' says where to put version B. The default setting, which produces the results shown above, looks like this: "#ifdef NEW\n%a#else /* NEW */\n%b#endif /* NEW */\n"  File: emacs, Node: Fine Points of Emerge, Prev: Combining in Emerge, Up: Emerge Fine Points of Emerge --------------------- During the merge, you mustn't try to edit the A and B buffers yourself. Emerge modifies them temporarily, but ultimately puts them back the way they were. You can have any number of merges going at once--just don't use any one buffer as input to more than one merge at once, since the temporary changes made in these buffers would get in each other's way. Starting Emerge can take a long time because it needs to compare the files fully. Emacs can't do anything else until `diff' finishes. Perhaps in the future someone will change Emerge to do the comparison in the background when the input files are large--then you could keep on doing other things with Emacs until Emerge gets ready to accept commands. After setting up the merge, Emerge runs the hook `emerge-startup-hook' (*note Hooks::.).  File: emacs, Node: C Mode, Next: Fortran, Prev: Emerge, Up: Programs C Mode ====== This section describes special features available in C mode, C++ mode and Objective C mode. * Menu: * Motion in C:: * Electric C:: * Hungry Delete:: * Other C Commands:: * Comments in C::  File: emacs, Node: Motion in C, Next: Electric C, Up: C Mode C Mode Motion Commands ---------------------- This section commands for moving point, in C mode and related modes. `C-c C-u' Move point back to the containing preprocessor conditional, leaving the mark behind. A prefix argument acts as a repeat count. With a negative argument, move the point forward to the end of the containing preprocessor conditional. When going backwards, `#elif' is treated like `#else' followed by `#if'. When going forwards, `#elif' is ignored. `C-c C-p' Move point back over a preprocessor conditional, leaving the mark behind. A prefix argument acts as a repeat count. With a negative argument, move forward. `C-c C-n' Move point forward across a preprocessor conditional, leaving the mark behind. A prefix argument acts as a repeat count. With a negative argument, move backward. `M-a' Move point to the beginning of the innermost C statement. If point is already at the beginning of a statement, it moves to the beginning of the preceding statement. With prefix argument N, move back N - 1 statements. If point is within a string or comment, or next to a comment (only whitespace between them), this command moves by sentences instead of statements. When called from a program, this function takes two optional arguments: the numeric prefix argument, and a buffer position limit (don't move back before that place). `M-e' Move point to the end of the innermost C statement. If point is at the end of a statement, move to the end of the next statement. With prefix argument N, move forward N - 1 statements. If point is within a string or comment, or next to a comment (only whitespace between them), this command moves by sentences instead of statements. When called from a program, this function takes two optional arguments: the numeric prefix argument, and a buffer position limit (don't move past that place). `M-x c-backward-into-nomenclature' Move point backward to beginning of a C++ nomenclature section or word. With prefix argument N, move N times. If N is negative, move forward. `M-x c-forward-into-nomenclature' Move the point forward to end of a C++ nomenclature section or word. With prefix argument N, move N times.  File: emacs, Node: Electric C, Next: Hungry Delete, Prev: Motion in C, Up: C Mode Electric C Characters --------------------- In C mode and related modes, certain printing characters are "electric"-in addition to inserting themselves, they also reindent the current line and may insert newlines. This feature is controlled by the variable `c-auto-newline'. The "electric" characters are `{', `}', `:', `#', `;', `,', `/' and `*'. Electric characters insert newlines only when the "auto-newline" feature is enabled (indicated by `/a' in the mode line after the mode name). This feature is controlled by the variable `c-auto-newline'. You can turn this feature on or off with the command `C-c C-a': `C-c C-a' Toggle the auto-newline feature (`c-toggle-auto-state'. With a prefix argument, this command turns the auto-newline feature on if the argument is positive, and off if it is negative. The colon character is electric because that is appropriate for a single colon. But when you want to insert a double colon in C++, the electric behavior of colon is inconvenient. You can insert a double colon with no reindentation or newlines by typing `C-c :': `C-c :' Insert a double colon scope operator at point, without reindenting the line or adding any newlines (`c-scope-operator'). The electric `#' key reindents the line if it appears to be the beginning of a preprocessor directive. This happens when the value of `c-electric-pound-behavior' is `(alignleft)'. You can turn this feature off by setting `c-electric-pound-behavior' to `nil'. The variable `c-hanging-braces-alist' controls the insertion of newlines before and after inserted braces. It is an association list with elements of the following form: `(SYNTACTIC-SYMBOL . NL-LIST)'. Most of the syntactic symbols that appear in `c-offsets-alist' are meaningful here as well. The list NL-LIST may contain either of the symbols `before' or `after', or both; or it may be `nil'. When a brace is inserted, the syntactic context it defines is looked up in `c-hanging-braces-alist'; if it is found, the NL-LIST is used to determine where newlines are inserted. If not found, the default is to insert a newline both before and after braces. The variable `c-hanging-colons-alist' controls the insertion of newlines before and after inserted colons. It is an association list with elements of the following form: `(SYNTACTIC-SYMBOL . NL-LIST)'. The list NL-LIST may contain either of the symbols `before' or `after', or both; or it may be `nil'. When a colon is inserted, the language element that it defines is looked up in this list, and if found, the NL-LIST is used to determine where newlines are inserted. If the language element for the colon is not found in this list, no newlines are inserted. Electric characters can also delete newlines automatically when the auto-newline feature is enabled. This feature makes auto-newline more acceptable, by deleting the newlines in the most common cases where you do not want them. Emacs can recognize several cases in which deleting a newline might be desirable; by setting the variable `c-cleanup-list', you can specify *which* of these cases that should happen. The variable's value is a list of symbols, each describing one case for possible deletion of a newline. Here are the meaningful symbols, and their meanings: `brace-else-brace' Clean up `} else {' constructs by placing entire construct on a single line. The clean-up occurs when you type the `{' after the `else', but only if there is nothing but white space between the braces and the `else'. `empty-defun-braces' Clean up empty defun braces by placing the braces on the same line. Clean-up occurs when you type the closing brace. `defun-close-semi' Clean up the semicolon after a `struct' or similar type declaration, by placing the semicolon on the same line as the closing brace. Clean-up occurs when you type the semicolon. `list-close-comma' Clean up commas following braces in array and aggregate initializers. Clean-up occurs when you type the comma. `scope-operator' Clean up double colons which may designate a C++ scope operator, by placing the colons together. Clean-up occurs when you type the second colon, but only when the two colons are separated by nothing but whitespace.  File: emacs, Node: Hungry Delete, Next: Other C Commands, Prev: Electric C, Up: C Mode Hungry Delete Feature in C -------------------------- When the "hungry-delete" feature is enabled (indicated by `/h' or `/ah' in the mode line after the mode name), a single DEL command deletes all preceding whitespace, not just one space. To turn this feature on or off, use `C-c C-d': `C-c C-d' Toggle the hungry-delete feature (`c-toggle-hungry-state'. With a prefix argument, this command turns the auto-newline feature on if the argument is positive, and off if it is negative. `C-c C-t' Toggle the auto-newline and hungry-delete features, both at once (`c-toggle-auto-hungry-state'. The variable `c-hungry-delete-key' controls whether the hungry-delete feature is enabled.  File: emacs, Node: Other C Commands, Next: Comments in C, Prev: Hungry Delete, Up: C Mode Other Commands for C Mode ------------------------- `C-M-h' Put mark at the end of a function definition, and put point at the beginning (`c-mark-function'). `M-q' Fill a paragraph, handling C and C++ comments (`c-fill-paragraph'). If any part of the current line is a comment or within a comment, this command fills the comment or the paragraph of it that point is in, preserving the comment indentation and comment delimiters. `C-c C-e' Run the C preprocessor on the text in the region, and show the result, which includes the expansion of all the macro calls (`c-macro-expand'). The buffer text before the region is also included in preprocessing, for the sake of macros defined there, but the output from this part isn't shown. When you are debugging C code that uses macros, sometimes it is hard to figure out precisely how the macros expand. With this command, you don't have to figure it out; you can see the results. `C-c C-\' Insert or align `\' characters at the ends of the lines of the region (`c-backslash-region'). This is useful after writing or editing a C macro definition. If a line already ends in `\', this command adjusts the amount of whitespace before it. Otherwise, it inserts a new `\'. However, the last line in the region is treated specially; no `\' is inserted on that line, and any `\' there is deleted. `M-x cpp-highlight-buffer' Highlight parts of the text according to its preprocessor conditionals. This command displays another buffer named `*CPP Edit*', which serves as a graphic menu for selecting how to display particular kinds of conditionals and their contents. After changing various settings, click on `[A]pply these settings' (or go to that buffer and type `a') to rehighlight the C mode buffer accordingly. `C-c C-s' Display the syntactic information about the current source line (`c-show-syntactic-information'). This is the information that directs how the line is indented.