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This is Info file ../info/emacs, produced by Makeinfo-1.63 from the input file emacs.texi. 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: List Tags, 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: List Tags, Prev: Tags Search, 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 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 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': Select the previous difference. Select the next difference. Choose the A version of this difference. 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. 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 point. `i b' Insert the B version of this difference at point. Put point and mark around the difference. 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 (*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 is 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, C++, Objective-C and Java modes. * 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 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, move 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. C++ nomenclature means a symbol name in the style of NamingSymbolsWithMixedCaseAndNoUnderlines; each capital letter begins a section or word. In the GNU project, we recommend using underscores to separate words within an identifier in C or C++, rather than using case distinctions. `M-x c-forward-into-nomenclature' Move 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: either before the brace, after, or both. 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 syntactic symbol it defines is looked up in this list, and if found, the NL-LIST is used to determine where newlines are inserted: either before the brace, after, or both. If the syntactic symbol 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 hungry-delete 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 expansions. `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. File: emacs, Node: Comments in C, Prev: Other C Commands, Up: C Mode Comments in C Modes ------------------- C mode and related modes use a number of variables for controlling comment format. `c-block-comments-indent-p' This variable specifies how to reindent block comments. The C modes support five styles of block comments: style 1: style 2 (GNU): style 3: style 4: style 5: /* /* Blah /* /* /* blah blah. */ * blah ** blah blah blah * blah ** blah blah */ */ */ */ For the styles 1 through 4, `c-block-comments-indent-p' should be `nil' (the default). If you want to use style 5, set `c-block-comments-indent-p' to `t'. This variable has no effect on the indentation of the comment-start itself or on insertion of asterisks when auto-filling C comments. It does not affect `M-q' either. `c-comment-only-line-offset' Extra offset for line which contains only the start of a comment. It can be either an integer or a cons cell of the form `(NON-ANCHORED-OFFSET . ANCHORED-OFFSET)', where NON-ANCHORED-OFFSET is the amount of offset given to non-column-zero anchored comment-only lines, and ANCHORED-OFFSET is the amount of offset to give column-zero anchored comment-only lines. Just an integer as value is equivalent to `(VAL . 0)'. `c-comment-start-regexp' This buffer-local variable specifies how to recognize the start of a comment. `c-hanging-comment-ender-p' If this variable is `nil', `c-fill-paragraph' leaves the comment terminator of a block comment on a line by itself. The default value is `t', which always puts the comment-end delimiter `*/' at the end of the last line of the comment text. 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 its 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. 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.) The variable `fortran-continuation-string' specifies what character to put on column 5. 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. File: emacs, Node: ForIndent Num, Next: ForIndent Conv, Prev: ForIndent Cont, Up: Fortran Indent Line Numbers ............ If a number is the first non-whitespace in the line, Fortran indentation assumes it is a line number and moves it to columns 0 through 4. (Columns always count from 0 in GNU Emacs.) Line numbers of four digits or less are normally indented one space. The variable `fortran-line-number-indent' controls this; it specifies the maximum indentation a line number can have. Line numbers are indented to right-justify them to end in column 4 unless that would require more than this maximum indentation. The default value of the variable is 1. Simply inserting a line number is enough to indent it according to these rules. As each digit is inserted, the indentation is recomputed. To turn off this feature, set the variable `fortran-electric-line-number' to `nil'. Then inserting line numbers is like inserting anything else. File: emacs, Node: ForIndent Conv, Next: ForIndent Vars, Prev: ForIndent Num, Up: Fortran Indent Syntactic Conventions ..................... Fortran mode assumes that you follow certain conventions that simplify the task of understanding a Fortran program well enough to indent it properly: * Two nested `do' loops never share a `continue' statement. * Fortran keywords such as `if', `else', `then', `do' and others are written without embedded whitespace or line breaks. Fortran compilers generally ignore whitespace outside of string constants, but Fortran mode does not recognize these keywords if they are not contiguous. Constructs such as `else if' or `end do' are acceptable, but the second word should be on the same line as the first and not on a continuation line. If you fail to follow these conventions, the indentation commands may indent some lines unaesthetically. However, a correct Fortran program retains its meaning when reindented even if the conventions are not followed. File: emacs, Node: ForIndent Vars, Prev: ForIndent Conv, Up: Fortran Indent Variables for Fortran Indentation ................................. Several additional variables control how Fortran indentation works: `fortran-do-indent' Extra indentation within each level of `do' statement (default 3). `fortran-if-indent' Extra indentation within each level of `if' statement (default 3). This value is also used for extra indentation within each level of the Fortran 90 `where' statement. `fortran-structure-indent' Extra indentation within each level of `structure', `union', or `map' statements (default 3). `fortran-continuation-indent' Extra indentation for bodies of continuation lines (default 5). `fortran-check-all-num-for-matching-do' If this is `nil', indentation assumes that each `do' statement ends on a `continue' statement. Therefore, when computing indentation for a statement other than `continue', it can save time by not checking for a `do' statement ending there. If this is non-`nil', indenting any numbered statement must check for a `do' that ends there. The default is `nil'. `fortran-blink-matching-if' If this is `t', indenting an `endif' statement moves the cursor momentarily to the matching `if' statement to show where it is. The default is `nil'. `fortran-minimum-statement-indent-fixed' Minimum indentation for fortran statements when using fixed format continuation line style. Statement bodies are never indented less than this much. The default is 6. `fortran-minimum-statement-indent-tab' Minimum indentation for fortran statements for tab format continuation line style. Statement bodies are never indented less than this much. The default is 8. File: emacs, Node: Fortran Comments, Next: Fortran Autofill, Prev: Fortran Indent, Up: Fortran Fortran Comments ---------------- The usual Emacs comment commands assume that a comment can follow a line of code. In Fortran, the standard comment syntax requires an entire line to be just a comment. Therefore, Fortran mode replaces the standard Emacs comment commands and defines some new variables. Fortran mode can also handle a nonstandard comment syntax where comments start with `!' and can follow other text. Because only some Fortran compilers accept this syntax, Fortran mode will not insert such comments unless you have said in advance to do so. To do this, set the variable `comment-start' to `"!"' (*note Variables::.). `M-;' Align comment or insert new comment (`fortran-comment-indent'). `C-x ;' Applies to nonstandard `!' comments only. `C-c ;' Turn all lines of the region into comments, or (with argument) turn them back into real code (`fortran-comment-region'). `M-;' in Fortran mode is redefined as the command `fortran-comment-indent'. Like the usual `M-;' command, this recognizes any kind of existing comment and aligns its text appropriately; if there is no existing comment, a comment is inserted and aligned. But inserting and aligning comments are not the same in Fortran mode as in other modes. When a new comment must be inserted, if the current line is blank, a full-line comment is inserted. On a non-blank line, a nonstandard `!' comment is inserted if you have said you want to use them. Otherwise a full-line comment is inserted on a new line before the current line. Nonstandard `!' comments are aligned like comments in other languages, but full-line comments are different. In a standard full-line comment, the comment delimiter itself must always appear in column zero. What can be aligned is the text within the comment. You can choose from three styles of alignment by setting the variable `fortran-comment-indent-style' to one of these values: `fixed' Align the text at a fixed column, which is the sum of `fortran-comment-line-extra-indent' and the minimum statement indentation. This is the default. The minimum statement indentation is `fortran-minimum-statement-indent-fixed' for fixed format continuation line style and `fortran-minimum-statement-indent-tab' for tab format style. `relative' Align the text as if it were a line of code, but with an additional `fortran-comment-line-extra-indent' columns of indentation. `nil' Don't move text in full-line columns automatically at all. In addition, you can specify the character to be used to indent within full-line comments by setting the variable `fortran-comment-indent-char' to the single-character string you want to use. Fortran mode introduces two variables `comment-line-start' and `comment-line-start-skip' which play for full-line comments the same roles played by `comment-start' and `comment-start-skip' for ordinary text-following comments. Normally these are set properly by Fortran mode so you do not need to change them. The normal Emacs comment command `C-x ;' has not been redefined. If you use `!' comments, this command can be used with them. Otherwise it is useless in Fortran mode. The command `C-c ;' (`fortran-comment-region') turns all the lines of the region into comments by inserting the string `C$$$' at the front of each one. With a numeric argument, it turns the region back into live code by deleting `C$$$' from the front of each line in it. The string used for these comments can be controlled by setting the variable `fortran-comment-region'. Note that here we have an example of a command and a variable with the same name; these two uses of the name never conflict because in Lisp and in Emacs it is always clear from the context which one is meant.