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GNU Info File | 1993-07-18 | 50KB | 901 lines

This is Info file ../info/emacs, produced by Makeinfo-1.54 from the input file emacs.texi. File: emacs, Node: Comments, Next: Balanced Editing, Prev: Matching, Up: Programs 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'). `M-x comment-region' Add or remove comment delimiters on all the lines in the region. The command that creates a comment is `M-;' (`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. `M-;' 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 ;; 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. The `M-x comment-region' command adds comment delimiters to the lines that start in the region, thus commenting them out. With a negative argument, it does the opposite--it deletes comment delimiters from the lines in the region. With a positive argument, `comment-region' adds comment delimiters and duplicates the last character of the comment start sequence as many times as the argument specifies. Thus, in Lisp mode, `C-u 2 M-x comment-region' adds `;;' to each line. Duplicating the comment delimiter is a way of calling attention to the comment. It can also affect how the comment is indented. In Lisp, for proper indentation, you should use an argument of two, if between defuns, and three, if within a defun. 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 `M-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 `M-;' 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. The variable `comment-column' is per-buffer: setting the variable in the normal fashion affects only the current buffer, but there is a default value which you can change with `setq-default'. *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 `" */"'. The variable `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-function' 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, Next: Symbol Completion, Prev: Comments, Up: Programs 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 can 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: 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 tag table (*note Tags::.); the legitimate symbol names are the tag names listed in the tag 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'. 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 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' 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 have a special major mode that facilitates scrolling and examining other manual pages. 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 and the current date. 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 (rms@mole.gnu.ai.mit.edu) * man.el: Rename functions and variables `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 (rms@mole.gnu.ai.mit.edu) * 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. Each bunch of grouped item 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. File: emacs, Node: Tags, Next: Emerge, Prev: Change Log, Up: Programs 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 (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 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. Each name recorded is called a "tag". * Menu: * Tag Syntax:: Tag syntax for various types of code and text files. * Create Tag Table:: Creating a tag table with `etags'. * Select Tag Table:: How to visit a tag table. * Find Tag:: Commands to find the definition of a specific tag. * Tags Search:: Using a tag table for searching and replacing. * Tags Stepping:: Visiting files in a tag table, one by one. * List Tags:: Listing and finding tags defined in a file. File: emacs, Node: Tag Syntax, Next: Create Tag 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 is a tag, and so is any typedef if `-t' is specified when the tag table is constructed. 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 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' and `\typeout' is a tag. File: emacs, Node: Create Tag Table, Next: Select Tag Table, Prev: Tag Syntax, Up: Tags Creating Tag Tables ------------------- The `etags' program is used to create a tag 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 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 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 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, Next: Find Tag, Prev: Create Tag Table, Up: Tags 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'; that value tells all the commands for working with tag tables that they must ask for a tag table file name to use. Using `visit-tags-table' to load a new tag table does not discard the other tables previously loaded. The other tags commands use all the tag tables that are loaded; the first one they use is the one that mentions the current visited file. You can specify a precise list of tag 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. File: emacs, Node: Find Tag, Next: Tags Search, Prev: Select Tag Table, Up: Tags 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 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. `M-x find-tag-regexp RET PATTERN RET' Find a tag whose name matches PATTERN. `C-u M-x find-tag-regexp' 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 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 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 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 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 new command `M-x 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. Emacs comes with a tag table file `src/TAGS' that 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 find the source for any Emacs function. File: emacs, Node: Tags Search, Next: Tags Stepping, Prev: Find Tag, Up: Tags 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 searches for matches in all the files in the selected tag 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 tag table. `M-x tags-query-replace' performs a single `query-replace' through all the files in the tag 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 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. The commands in this section carry out much broader searches than the `find-tags' family. The `find-tags' 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 mostly the same as running a compilation and having Emacs show you where the errors were. *Note Compilation::. File: emacs, Node: Tags Stepping, Next: List Tags, Prev: Tags Search, Up: Tags Stepping Through a Tag Table ---------------------------- If you wish to process all the files in the selected tag 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 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. You can also perform completion in the buffer on the name space of tag names in the current tag 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 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 part of the buffer agrees with the common ancestor, then the B version is preferred for that part. 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 prefix 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. If you abort Emerge with `C-]', the output is not saved. 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 Emerge commands are single characters, but ordinary Emacs commands are disabled. This is convenient if you use only Emerge commands. In Edit mode, all Emerge 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. 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: The difference is showing the A version. The `a' command always produces this state; the mode line indicates it with `A'. 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 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' at the end of each section. 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 prefix 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': Select the previous difference. Select the next difference. Choose the A version of this difference. Choose the B version of this difference. Select a particular difference; specify the sequence number of that difference as a prefix argument. Select the difference containing point. You can use this command in the merge buffer or in the A or B buffer. Quit--finish the merge. `C-]' Abort--exit merging and do not save the output. Go into Fast mode. (In Edit mode, this is actually `C-c C-c f'.) Go into Edit mode. 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 the point. `i b' Insert the B version of this difference at the point. Put the point and mark around the difference region. Scroll all three windows down (like `M-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. `x f' Show the files/buffers Emerge is operating on in 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 to 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 Emerge 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 locus. To do this, use `x c', which edits the merge buffer like this: #ifdef NEW VERSION FROM A FILE #else /* NEW */ VERSION FROM B FILE #endif /* NEW */ While this example shows C preprocessor conditionals delimiting the two alternative versions, you can specify the strings you want 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 ====== In addition to the facilities of typical programming language major modes (*note Program Modes::.), C mode has various special facilities. `M-a' `M-e' In C mode, `M-a' and `M-e' now move by complete C statements (`c-beginning-of-statement' and `c-end-of-statement'). These commands do ordinary, textual sentence motion when in or next to a comment. `M-q' `M-q' in C mode runs `c-fill-paragraph', which is designed for filling C comments. (We assume you don't want to fill the actual C code in a C program.) `C-c C-u' Move back to the containing preprocessor conditional, setting the mark at the starting point (`c-up-conditional'). A prefix argument acts as a repeat count. With a negative argument, this command moves forward to the end of the containing preprocessor conditional. When going backwards, `#elif' acts like `#else' followed by `#if'. When going forwards, `#elif' is ignored. `C-c C-n' Move forward across the next preprocessor conditional, setting the mark at the starting point (`c-forward-conditional'). `C-c C-p' Move backward across the previous preprocessor conditional, setting the at the starting point (`c-backward-conditional'). `M-x c-macro-expand' When you are debugging C code that uses macros, sometimes it is hard to figure out precisely how the macros expand. The command `M-x c-macro-expand' runs the C preprocessor and shows you what expansion results from the region. The portion of the buffer before the region is also included in preprocessing, for the sake of macros defined there, but the output from this part isn't shown. `M-x c-backslash-region' Insert or align `\' characters at the ends of the lines of the region, except for the last such line. 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 `\'. C++ mode is like C mode, except that it understands C++ comment syntax and certain other differences between C and C++. It also has a command `M-x fill-c++-comment', which fills a paragraph made of C++ comment lines. The command `comment-region' is useful in C++ mode for commenting out several consecutive lines, or removing the commenting out of such lines. (You don't need this command with C comment syntax because you don't need to put comment delimiters on each line.) *Note Comments::. File: emacs, Node: Fortran, Next: Asm Mode, Prev: C Mode, 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. Fortran mode has it's own Auto Fill mode that breaks long lines into proper Fortran continuation lines. 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. This command runs the hook `fortran-mode-hook' (*note Hooks::.). * Menu: * Motion: Fortran Motion. Moving point by statements or subprograms. * Indent: Fortran Indent. Indentation commands for Fortran. * Comments: Fortran Comments. Inserting and aligning comments. * Autofill: Fortran Autofill. Auto fill minor mode for Fortran. * Columns: Fortran Columns. Measuring columns for valid Fortran. * Abbrev: Fortran Abbrev. Built-in abbrevs for Fortran keywords. Fortran mode was contributed by Michael Prange. It has been updated by Stephen A. Wood who has collated the contributions and suggestions of many users. File: emacs, Node: Fortran Motion, Next: Fortran Indent, Up: Fortran 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, Next: Fortran Comments, Prev: Fortran Motion, Up: Fortran 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. * Contline: ForIndent Cont. How continuation lines indent. * 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, Next: ForIndent Cont, Up: Fortran Indent Fortran Indentation Commands ............................ `TAB' Indent the current line (`fortran-indent-line'). `LFD' Indent the current and start a new indented line (`fortran-indent-new-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'). Fortran mode redefines TAB to reindent the current line for Fortran (`fortran-indent-line'). This command indents Line numbers and continuation markers to their required columns, and independently indents the body of the statement based on its nesting in the program. The key `LFD' runs the command `fortran-indent-new-line', which reindents the current line then makes and indents a new line. This command is useful to reindent the closing statement of `do' loops and other blocks before starting a new line. The key `C-M-q' runs `fortran-indent-subprogram', a command to reindent all the lines of the Fortran subprogram (function or subroutine) containing point. The key `M-LFD' runs `fortran-split-line', which splits 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 Cont, Next: ForIndent Num, Prev: ForIndent Commands, Up: Fortran Indent Continuation Lines .................. Most modern Fortran compilers allow two ways of writing continuation lines. If the first non-space character on a line is in column 5, then that line is a continuation of the previous line. We call this "fixed format". (In GNU Emacs we always count columns from 0.) A line that starts with a tab character followed by any digit except `0' is also a continuation line. We call this style of continuation "tab format". Fortran mode can make either style of continuation line, but you must specify which one you prefer. The value of the variable `indent-tabs-mode' controls the choice: `nil' for fixed format, and non-`nil' for tab format. You can tell which style is presently in effect by the presence or absence of the string `Tab' in the mode line. If the text on a line starts with the conventional Fortran continuation marker `$', or if it begins with any non-whitespace character in column 5, Fortran mode treats it as a continuation line. When you indent a continuation line with TAB, it converts the line to the current continuation style. When you split a Fortran statement with `M-LFD', the continuation marker on the newline is created according to the continuation style. The setting of continuation style affects several other aspects of editing in Fortran mode. In fixed format mode, the minimum column number for the body of a statement is 6. Lines inside of Fortran blocks that are indented to larger column numbers always use only the space character for whitespace. In tab format mode, the minimum column number for the statement body is 8, and the whitespace before column 8 must always consist of one tab character. When you enter Fortran mode for an existing file, it tries to deduce the proper continuation style automatically from the file contents. The first line that begins with either a tab character or six spaces determines the choice. The variable `fortran-analyze-depth' specifies how many lines to consider (at the beginning of the file); if none of those lines indicates a style, then the variable `fortran-tab-mode-default' specifies the style. If it is `nil', that specifies fixed format, and non-`nil' specifies tab format.