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This is Info file ../../info/lispref.info, produced by Makeinfo-1.63 from the input file lispref.texi. Edition History: GNU Emacs Lisp Reference Manual Second Edition (v2.01), May 1993 GNU Emacs Lisp Reference Manual Further Revised (v2.02), August 1993 Lucid Emacs Lisp Reference Manual (for 19.10) First Edition, March 1994 XEmacs Lisp Programmer's Manual (for 19.12) Second Edition, April 1995 GNU Emacs Lisp Reference Manual v2.4, June 1995 XEmacs Lisp Programmer's Manual (for 19.13) Third Edition, July 1995 Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995 Free Software Foundation, Inc. Copyright (C) 1994, 1995 Sun Microsystems, Inc. Copyright (C) 1995 Amdahl Corporation. Copyright (C) 1995 Ben Wing. Permission is granted to make and distribute verbatim copies of this manual provided the copyright notice and this permission notice are preserved on all copies. Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one. Permission is granted to copy and distribute translations of this manual into another language, under the above conditions for modified versions, except that this permission notice may be stated in a translation approved by the Foundation. Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided also that the section entitled "GNU General Public License" is included exactly as in the original, and provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one. Permission is granted to copy and distribute translations of this manual into another language, under the above conditions for modified versions, except that the section entitled "GNU General Public License" may be included in a translation approved by the Free Software Foundation instead of in the original English. File: lispref.info, Node: Specification Examples, Prev: Backtracking, Up: Macro Calls Specification Examples ...................... This section provides several examples of Edebug specifications to show most of its capabilities. A `let' special form has a sequence of bindings and a body where each of the bindings is a symbol or a sublist with a symbol and optional value. In the specification below notice the `fence' inside of the sublist to prevent backtracking. (def-edebug-spec let ((&rest &or symbolp (fence symbolp &optional form)) body)) Here are the specifications for the `case' and `do' macros in `cl.el'. (Specifications for all the macros defined by `cl.el' (version 2.02) are in `cl-specs.el'.) (def-edebug-spec case (form &rest (sexp body))) (def-edebug-spec do ((&rest &or symbolp (symbolp &optional form form)) (form body) body)) Edebug uses the following specifications for `defun' and `defmacro' and the associated argument list and `interactive' specifications. It is necessary to specially process the argument of an interactive form to allow debugging of a list argument outside of the function body, while not stopping on the interactive form itself. (def-edebug-spec defmacro defun) ; Indirect ref to `defun' spec (def-edebug-spec defun (&define name lambda-list [&optional stringp] ; Match the doc string, if present. [&optional ("interactive" interactive)] def-body)) (def-edebug-spec lambda-list (([&rest arg] [&optional ["&optional" arg &rest arg]] &optional ["&rest" arg] ))) (def-edebug-spec interactive (&optional &or stringp def-form)) ; Notice: `def-form' The `backquote' specification illustrates how to use `nil' to terminate recursion. Also a vector may be matched. Note that backquote (``') is a macro that results in an expression that is not necessarily evaluated. It is often used to simplify the definition of a macro where the result of the macro call is evaluated, but Edebug does not know when this is the case. So do not be surprised when you cannot step through your backquoted code. However, `,' and `,@' forms within backquoted forms are evaluated and Edebug instruments them. Nested backquotes are supported to a limited extent. Quoted forms are not normally evaluated, but if the quoted form appears immediately within `,' and `,@' forms, Edebug treats this as a backquoted form at the next higher level. (def-edebug-spec ` (backquote-form)) (def-edebug-spec backquote-form (&or ([&or "," ",@"] &or ("quote" backquote-form) form) (backquote-form . [&or nil backquote-form]) (vector &rest backquote-form) sexp)) Finally, the standard functions `mapcar', `mapconcat', `mapatoms', `apply', and `funcall' all take function arguments. Here is one example: (def-edebug-spec apply (function-form &rest form)) File: lispref.info, Node: Edebug Options, Prev: Macro Calls, Up: Edebug Edebug Options -------------- These options affect the behavior of Edebug: - User Option: edebug-setup-hook Functions to call before Edebug is used. Each time it is set to a new function, Edebug will call that function once and then `edebug-setup-hook' is reset to `nil'. You could use this to load up Edebug specifications associated with a package you are using only when you also use Edebug. - User Option: edebug-all-defs If non-`nil', normal evaluation of any defining forms (e.g. `defun' and `defmacro') will instrument them for Edebug. This applies to `eval-defun', `eval-region', and `eval-current-buffer'. Use the command `edebug-all-defs' to toggle the value of this variable. You may want to make this variable local to each buffer by calling `(make-local-variable 'edebug-all-defs)' in your `emacs-lisp-mode-hook'. The default value is `nil'. - User Option: edebug-all-forms If non-`nil', normal evaluation of any forms by `eval-defun', `eval-region', and `eval-current-buffer' will instrument them for Edebug. Use the command `edebug-all-forms' to toggle the value of this option. - User Option: edebug-save-windows If non-`nil', save and restore window configuration on Edebug calls. It takes some time to save and restore, so if your program does not care what happens to the window configurations, it is better to set this variable to `nil'. - User Option: edebug-save-displayed-buffer-points If non-`nil', save and restore point in all displayed buffers. This is necessary if you are debugging code that changes the point of a buffer which is displayed in a non-selected window. If Edebug or the user then selects the window, the buffer's point will be changed to the window's point. This is an expensive operation since it visits each window and each displayed buffer twice for each Edebug activation, so it is best to avoid it if you can. - User Option: edebug-initial-mode If this variable is non-`nil', it specifies the initial execution mode for Edebug when it is first activated. Possible values are `step', `next', `go', `Go-nonstop', `trace', `Trace-fast', `continue', and `Continue-fast'. The default value is `step'. - User Option: edebug-trace Non-`nil' means display a trace of function entry and exit. Tracing output is displayed in a buffer named `*edebug-trace*', one function entry or exit per line, indented by the recursion level. You can customize this display by replacing functions `edebug-print-trace-before' and `edebug-print-trace-after'. The default value is `nil'. - User Option: edebug-test-coverage If non-`nil', Edebug tests coverage of all expressions debugged. This is done by comparing the result of each expression with the previous result. Coverage is considered OK if two different results are found. So to sufficiently test the coverage of your code, try to execute it under conditions that evaluate all expressions more than once, and produce different results for each expression. Use `edebug-display-freq-count' to display the frequency count and coverage information for a definition. - User Option: edebug-continue-kbd-macro If non-`nil', continue defining or executing any keyboard macro that is executing outside of Edebug. - User Option: edebug-print-length If non-`nil', set `print-length' to this while printing results in Edebug. The default value is `50'. - User Option: edebug-print-level If non-`nil', set `print-level' to this while printing results in Edebug. The default value is `50'. - User Option: edebug-print-circle If non-`nil', set `print-circle' to this while printing results in Edebug. The default value is `nil'. File: lispref.info, Node: Read and Print, Next: Minibuffers, Prev: Debugging, Up: Top Reading and Printing Lisp Objects ********************************* "Printing" and "reading" are the operations of converting Lisp objects to textual form and vice versa. They use the printed representations and read syntax described in *Note Lisp Data Types::. This chapter describes the Lisp functions for reading and printing. It also describes "streams", which specify where to get the text (if reading) or where to put it (if printing). * Menu: * Streams Intro:: Overview of streams, reading and printing. * Input Streams:: Various data types that can be used as input streams. * Input Functions:: Functions to read Lisp objects from text. * Output Streams:: Various data types that can be used as output streams. * Output Functions:: Functions to print Lisp objects as text. * Output Variables:: Variables that control what the printing functions do. File: lispref.info, Node: Streams Intro, Next: Input Streams, Up: Read and Print Introduction to Reading and Printing ==================================== "Reading" a Lisp object means parsing a Lisp expression in textual form and producing a corresponding Lisp object. This is how Lisp programs get into Lisp from files of Lisp code. We call the text the "read syntax" of the object. For example, the text `(a . 5)' is the read syntax for a cons cell whose CAR is `a' and whose CDR is the number 5. "Printing" a Lisp object means producing text that represents that object--converting the object to its printed representation. Printing the cons cell described above produces the text `(a . 5)'. Reading and printing are more or less inverse operations: printing the object that results from reading a given piece of text often produces the same text, and reading the text that results from printing an object usually produces a similar-looking object. For example, printing the symbol `foo' produces the text `foo', and reading that text returns the symbol `foo'. Printing a list whose elements are `a' and `b' produces the text `(a b)', and reading that text produces a list (but not the same list) with elements `a' and `b'. However, these two operations are not precisely inverses. There are three kinds of exceptions: * Printing can produce text that cannot be read. For example, buffers, windows, frames, subprocesses and markers print into text that starts with `#'; if you try to read this text, you get an error. There is no way to read those data types. * One object can have multiple textual representations. For example, `1' and `01' represent the same integer, and `(a b)' and `(a . (b))' represent the same list. Reading will accept any of the alternatives, but printing must choose one of them. * Comments can appear at certain points in the middle of an object's read sequence without affecting the result of reading it. File: lispref.info, Node: Input Streams, Next: Input Functions, Prev: Streams Intro, Up: Read and Print Input Streams ============= Most of the Lisp functions for reading text take an "input stream" as an argument. The input stream specifies where or how to get the characters of the text to be read. Here are the possible types of input stream: BUFFER The input characters are read from BUFFER, starting with the character directly after point. Point advances as characters are read. MARKER The input characters are read from the buffer that MARKER is in, starting with the character directly after the marker. The marker position advances as characters are read. The value of point in the buffer has no effect when the stream is a marker. STRING The input characters are taken from STRING, starting at the first character in the string and using as many characters as required. FUNCTION The input characters are generated by FUNCTION, one character per call. Normally FUNCTION is called with no arguments, and should return a character. Occasionally FUNCTION is called with one argument (always a character). When that happens, FUNCTION should save the argument and arrange to return it on the next call. This is called "unreading" the character; it happens when the Lisp reader reads one character too many and wants to "put it back where it came from". `t' `t' used as a stream means that the input is read from the minibuffer. In fact, the minibuffer is invoked once and the text given by the user is made into a string that is then used as the input stream. `nil' `nil' supplied as an input stream means to use the value of `standard-input' instead; that value is the "default input stream", and must be a non-`nil' input stream. SYMBOL A symbol as input stream is equivalent to the symbol's function definition (if any). Here is an example of reading from a stream that is a buffer, showing where point is located before and after: ---------- Buffer: foo ---------- This-!- is the contents of foo. ---------- Buffer: foo ---------- (read (get-buffer "foo")) => is (read (get-buffer "foo")) => the ---------- Buffer: foo ---------- This is the-!- contents of foo. ---------- Buffer: foo ---------- Note that the first read skips a space. Reading skips any amount of whitespace preceding the significant text. In Emacs 18, reading a symbol discarded the delimiter terminating the symbol. Thus, point would end up at the beginning of `contents' rather than after `the'. The Emacs 19 behavior is superior because it correctly handles input such as `bar(foo)', where the open-parenthesis that ends one object is needed as the beginning of another object. Here is an example of reading from a stream that is a marker, initially positioned at the beginning of the buffer shown. The value read is the symbol `This'. ---------- Buffer: foo ---------- This is the contents of foo. ---------- Buffer: foo ---------- (setq m (set-marker (make-marker) 1 (get-buffer "foo"))) => #<marker at 1 in foo> (read m) => This m => #<marker at 5 in foo> ;; Before the first space. Here we read from the contents of a string: (read "(When in) the course") => (When in) The following example reads from the minibuffer. The prompt is: `Lisp expression: '. (That is always the prompt used when you read from the stream `t'.) The user's input is shown following the prompt. (read t) => 23 ---------- Buffer: Minibuffer ---------- Lisp expression: `23 RET' ---------- Buffer: Minibuffer ---------- Finally, here is an example of a stream that is a function, named `useless-stream'. Before we use the stream, we initialize the variable `useless-list' to a list of characters. Then each call to the function `useless-stream' obtains the next character in the list or unreads a character by adding it to the front of the list. (setq useless-list (append "XY()" nil)) => (88 89 40 41) (defun useless-stream (&optional unread) (if unread (setq useless-list (cons unread useless-list)) (prog1 (car useless-list) (setq useless-list (cdr useless-list))))) => useless-stream Now we read using the stream thus constructed: (read 'useless-stream) => XY useless-list => (40 41) Note that the open and close parentheses remains in the list. The Lisp reader encountered the open parenthesis, decided that it ended the input, and unread it. Another attempt to read from the stream at this point would read `()' and return `nil'. - Function: get-file-char This function is used internally as an input stream to read from the input file opened by the function `load'. Don't use this function yourself. File: lispref.info, Node: Input Functions, Next: Output Streams, Prev: Input Streams, Up: Read and Print Input Functions =============== This section describes the Lisp functions and variables that pertain to reading. In the functions below, STREAM stands for an input stream (see the previous section). If STREAM is `nil' or omitted, it defaults to the value of `standard-input'. An `end-of-file' error is signaled if reading encounters an unterminated list, vector, or string. - Function: read &optional STREAM This function reads one textual Lisp expression from STREAM, returning it as a Lisp object. This is the basic Lisp input function. - Function: read-from-string STRING &optional START END This function reads the first textual Lisp expression from the text in STRING. It returns a cons cell whose CAR is that expression, and whose CDR is an integer giving the position of the next remaining character in the string (i.e., the first one not read). If START is supplied, then reading begins at index START in the string (where the first character is at index 0). If END is also supplied, then reading stops just before that index, as if the rest of the string were not there. For example: (read-from-string "(setq x 55) (setq y 5)") => ((setq x 55) . 11) (read-from-string "\"A short string\"") => ("A short string" . 16) ;; Read starting at the first character. (read-from-string "(list 112)" 0) => ((list 112) . 10) ;; Read starting at the second character. (read-from-string "(list 112)" 1) => (list . 5) ;; Read starting at the seventh character, ;; and stopping at the ninth. (read-from-string "(list 112)" 6 8) => (11 . 8) - Variable: standard-input This variable holds the default input stream--the stream that `read' uses when the STREAM argument is `nil'. File: lispref.info, Node: Output Streams, Next: Output Functions, Prev: Input Functions, Up: Read and Print Output Streams ============== An output stream specifies what to do with the characters produced by printing. Most print functions accept an output stream as an optional argument. Here are the possible types of output stream: BUFFER The output characters are inserted into BUFFER at point. Point advances as characters are inserted. MARKER The output characters are inserted into the buffer that MARKER points into, at the marker position. The marker position advances as characters are inserted. The value of point in the buffer has no effect on printing when the stream is a marker. FUNCTION The output characters are passed to FUNCTION, which is responsible for storing them away. It is called with a single character as argument, as many times as there are characters to be output, and is free to do anything at all with the characters it receives. `t' The output characters are displayed in the echo area. `nil' `nil' specified as an output stream means to the value of `standard-output' instead; that value is the "default output stream", and must be a non-`nil' output stream. SYMBOL A symbol as output stream is equivalent to the symbol's function definition (if any). Many of the valid output streams are also valid as input streams. The difference between input and output streams is therefore mostly one of how you use a Lisp object, not a distinction of types of object. Here is an example of a buffer used as an output stream. Point is initially located as shown immediately before the `h' in `the'. At the end, point is located directly before that same `h'. ---------- Buffer: foo ---------- This is t-!-he contents of foo. ---------- Buffer: foo ---------- (print "This is the output" (get-buffer "foo")) => "This is the output" ---------- Buffer: foo ---------- This is t "This is the output" -!-he contents of foo. ---------- Buffer: foo ---------- Now we show a use of a marker as an output stream. Initially, the marker is in buffer `foo', between the `t' and the `h' in the word `the'. At the end, the marker has advanced over the inserted text so that it remains positioned before the same `h'. Note that the location of point, shown in the usual fashion, has no effect. ---------- Buffer: foo ---------- "This is the -!-output" ---------- Buffer: foo ---------- m => #<marker at 11 in foo> (print "More output for foo." m) => "More output for foo." ---------- Buffer: foo ---------- "This is t "More output for foo." he -!-output" ---------- Buffer: foo ---------- m => #<marker at 35 in foo> The following example shows output to the echo area: (print "Echo Area output" t) => "Echo Area output" ---------- Echo Area ---------- "Echo Area output" ---------- Echo Area ---------- Finally, we show the use of a function as an output stream. The function `eat-output' takes each character that it is given and conses it onto the front of the list `last-output' (*note Building Lists::.). At the end, the list contains all the characters output, but in reverse order. (setq last-output nil) => nil (defun eat-output (c) (setq last-output (cons c last-output))) => eat-output (print "This is the output" 'eat-output) => "This is the output" last-output => (10 34 116 117 112 116 117 111 32 101 104 116 32 115 105 32 115 105 104 84 34 10) Now we can put the output in the proper order by reversing the list: (concat (nreverse last-output)) => " \"This is the output\" " Calling `concat' converts the list to a string so you can see its contents more clearly. File: lispref.info, Node: Output Functions, Next: Output Variables, Prev: Output Streams, Up: Read and Print Output Functions ================ This section describes the Lisp functions for printing Lisp objects. Some of the XEmacs printing functions add quoting characters to the output when necessary so that it can be read properly. The quoting characters used are `"' and `\'; they distinguish strings from symbols, and prevent punctuation characters in strings and symbols from being taken as delimiters when reading. *Note Printed Representation::, for full details. You specify quoting or no quoting by the choice of printing function. If the text is to be read back into Lisp, then it is best to print with quoting characters to avoid ambiguity. Likewise, if the purpose is to describe a Lisp object clearly for a Lisp programmer. However, if the purpose of the output is to look nice for humans, then it is better to print without quoting. Printing a self-referent Lisp object requires an infinite amount of text. In certain cases, trying to produce this text leads to a stack overflow. XEmacs detects such recursion and prints `#LEVEL' instead of recursively printing an object already being printed. For example, here `#0' indicates a recursive reference to the object at level 0 of the current print operation: (setq foo (list nil)) => (nil) (setcar foo foo) => (#0) In the functions below, STREAM stands for an output stream. (See the previous section for a description of output streams.) If STREAM is `nil' or omitted, it defaults to the value of `standard-output'. - Function: print OBJECT &optional STREAM The `print' function is a convenient way of printing. It outputs the printed representation of OBJECT to STREAM, printing in addition one newline before OBJECT and another after it. Quoting characters are used. `print' returns OBJECT. For example: (progn (print 'The\ cat\ in) (print "the hat") (print " came back")) -| -| The\ cat\ in -| -| "the hat" -| -| " came back" -| => " came back" - Function: prin1 OBJECT &optional STREAM This function outputs the printed representation of OBJECT to STREAM. It does not print newlines to separate output as `print' does, but it does use quoting characters just like `print'. It returns OBJECT. (progn (prin1 'The\ cat\ in) (prin1 "the hat") (prin1 " came back")) -| The\ cat\ in"the hat"" came back" => " came back" - Function: princ OBJECT &optional STREAM This function outputs the printed representation of OBJECT to STREAM. It returns OBJECT. This function is intended to produce output that is readable by people, not by `read', so it doesn't insert quoting characters and doesn't put double-quotes around the contents of strings. It does not add any spacing between calls. (progn (princ 'The\ cat) (princ " in the \"hat\"")) -| The cat in the "hat" => " in the \"hat\"" - Function: terpri &optional STREAM This function outputs a newline to STREAM. The name stands for "terminate print". - Function: write-char CHARACTER &optional STREAM This function outputs CHARACTER to STREAM. It returns CHARACTER. - Function: prin1-to-string OBJECT &optional NOESCAPE This function returns a string containing the text that `prin1' would have printed for the same argument. (prin1-to-string 'foo) => "foo" (prin1-to-string (mark-marker)) => "#<marker at 2773 in strings.texi>" If NOESCAPE is non-`nil', that inhibits use of quoting characters in the output. (This argument is supported in Emacs versions 19 and later.) (prin1-to-string "foo") => "\"foo\"" (prin1-to-string "foo" t) => "foo" See `format', in *Note String Conversion::, for other ways to obtain the printed representation of a Lisp object as a string. File: lispref.info, Node: Output Variables, Prev: Output Functions, Up: Read and Print Variables Affecting Output ========================== - Variable: standard-output The value of this variable is the default output stream--the stream that print functions use when the STREAM argument is `nil'. - Variable: print-escape-newlines If this variable is non-`nil', then newline characters in strings are printed as `\n' and formfeeds are printed as `\f'. Normally these characters are printed as actual newlines and formfeeds. This variable affects the print functions `prin1' and `print', as well as everything that uses them. It does not affect `princ'. Here is an example using `prin1': (prin1 "a\nb") -| "a -| b" => "a b" (let ((print-escape-newlines t)) (prin1 "a\nb")) -| "a\nb" => "a b" In the second expression, the local binding of `print-escape-newlines' is in effect during the call to `prin1', but not during the printing of the result. - Variable: print-length The value of this variable is the maximum number of elements of a list that will be printed. If a list being printed has more than this many elements, it is abbreviated with an ellipsis. If the value is `nil' (the default), then there is no limit. (setq print-length 2) => 2 (print '(1 2 3 4 5)) -| (1 2 ...) => (1 2 ...) - Variable: print-level The value of this variable is the maximum depth of nesting of parentheses and brackets when printed. Any list or vector at a depth exceeding this limit is abbreviated with an ellipsis. A value of `nil' (which is the default) means no limit. This variable exists in version 19 and later versions. File: lispref.info, Node: Minibuffers, Next: Command Loop, Prev: Read and Print, Up: Top Minibuffers *********** A "minibuffer" is a special buffer that XEmacs commands use to read arguments more complicated than the single numeric prefix argument. These arguments include file names, buffer names, and command names (as in `M-x'). The minibuffer is displayed on the bottom line of the frame, in the same place as the echo area, but only while it is in use for reading an argument. * Menu: * Intro to Minibuffers:: Basic information about minibuffers. * Text from Minibuffer:: How to read a straight text string. * Object from Minibuffer:: How to read a Lisp object or expression. * Minibuffer History:: Recording previous minibuffer inputs so the user can reuse them. * Completion:: How to invoke and customize completion. * Yes-or-No Queries:: Asking a question with a simple answer. * Multiple Queries:: Asking a series of similar questions. * Minibuffer Misc:: Various customization hooks and variables. File: lispref.info, Node: Intro to Minibuffers, Next: Text from Minibuffer, Up: Minibuffers Introduction to Minibuffers =========================== In most ways, a minibuffer is a normal XEmacs buffer. Most operations *within* a buffer, such as editing commands, work normally in a minibuffer. However, many operations for managing buffers do not apply to minibuffers. The name of a minibuffer always has the form ` *Minibuf-NUMBER', and it cannot be changed. Minibuffers are displayed only in special windows used only for minibuffers; these windows always appear at the bottom of a frame. (Sometime frames have no minibuffer window, and sometimes a special kind of frame contains nothing but a minibuffer window; see *Note Minibuffers and Frames::.) The minibuffer's window is normally a single line. You can resize it temporarily with the window sizing commands; it reverts to its normal size when the minibuffer is exited. You can resize it permanently by using the window sizing commands in the frame's other window, when the minibuffer is not active. If the frame contains just a minibuffer, you can change the minibuffer's size by changing the frame's size. If a command uses a minibuffer while there is an active minibuffer, this is called a "recursive minibuffer". The first minibuffer is named ` *Minibuf-0*'. Recursive minibuffers are named by incrementing the number at the end of the name. (The names begin with a space so that they won't show up in normal buffer lists.) Of several recursive minibuffers, the innermost (or most recently entered) is the active minibuffer. We usually call this "the" minibuffer. You can permit or forbid recursive minibuffers by setting the variable `enable-recursive-minibuffers' or by putting properties of that name on command symbols (*note Minibuffer Misc::.). Like other buffers, a minibuffer may use any of several local keymaps (*note Keymaps::.); these contain various exit commands and in some cases completion commands (*note Completion::.). * `minibuffer-local-map' is for ordinary input (no completion). * `minibuffer-local-ns-map' is similar, except that SPC exits just like RET. This is used mainly for Mocklisp compatibility. * `minibuffer-local-completion-map' is for permissive completion. * `minibuffer-local-must-match-map' is for strict completion and for cautious completion. File: lispref.info, Node: Text from Minibuffer, Next: Object from Minibuffer, Prev: Intro to Minibuffers, Up: Minibuffers Reading Text Strings with the Minibuffer ======================================== Most often, the minibuffer is used to read text as a string. It can also be used to read a Lisp object in textual form. The most basic primitive for minibuffer input is `read-from-minibuffer'; it can do either one. In most cases, you should not call minibuffer input functions in the middle of a Lisp function. Instead, do all minibuffer input as part of reading the arguments for a command, in the `interactive' spec. *Note Defining Commands::. - Function: read-from-minibuffer PROMPT-STRING &optional INITIAL-CONTENTS KEYMAP READ HIST This function is the most general way to get input through the minibuffer. By default, it accepts arbitrary text and returns it as a string; however, if READ is non-`nil', then it uses `read' to convert the text into a Lisp object (*note Input Functions::.). The first thing this function does is to activate a minibuffer and display it with PROMPT-STRING as the prompt. This value must be a string. Then, if INITIAL-CONTENTS is a string, `read-from-minibuffer' inserts it into the minibuffer, leaving point at the end. The minibuffer appears with this text as its contents. The value of INITIAL-CONTENTS may also be a cons cell of the form `(STRING . POSITION)'. This means to insert STRING in the minibuffer but put point POSITION characters from the beginning, rather than at the end. If KEYMAP is non-`nil', that keymap is the local keymap to use in the minibuffer. If KEYMAP is omitted or `nil', the value of `minibuffer-local-map' is used as the keymap. Specifying a keymap is the most important way to customize the minibuffer for various applications such as completion. The argument HIST specifies which history list variable to use for saving the input and for history commands used in the minibuffer. It defaults to `minibuffer-history'. *Note Minibuffer History::. When the user types a command to exit the minibuffer, `read-from-minibuffer' uses the text in the minibuffer to produce its return value. Normally it simply makes a string containing that text. However, if READ is non-`nil', `read-from-minibuffer' reads the text and returns the resulting Lisp object, unevaluated. (*Note Input Functions::, for information about reading.) - Function: read-string PROMPT &optional INITIAL This function reads a string from the minibuffer and returns it. The arguments PROMPT and INITIAL are used as in `read-from-minibuffer'. The keymap used is `minibuffer-local-map'. This is a simplified interface to the `read-from-minibuffer' function: (read-string PROMPT INITIAL) == (read-from-minibuffer PROMPT INITIAL nil nil nil) - Variable: minibuffer-local-map This is the default local keymap for reading from the minibuffer. By default, it makes the following bindings: LFD `exit-minibuffer' RET `exit-minibuffer' `C-g' `abort-recursive-edit' `M-n' `next-history-element' `M-p' `previous-history-element' `M-r' `next-matching-history-element' `M-s' `previous-matching-history-element' - Function: read-no-blanks-input PROMPT &optional INITIAL This function reads a string from the minibuffer, but does not allow whitespace characters as part of the input: instead, those characters terminate the input. The arguments PROMPT and INITIAL are used as in `read-from-minibuffer'. This is a simplified interface to the `read-from-minibuffer' function, and passes the value of the `minibuffer-local-ns-map' keymap as the KEYMAP argument for that function. Since the keymap `minibuffer-local-ns-map' does not rebind `C-q', it *is* possible to put a space into the string, by quoting it. (read-no-blanks-input PROMPT INITIAL) == (read-from-minibuffer PROMPT INITIAL minibuffer-local-ns-map) - Variable: minibuffer-local-ns-map This built-in variable is the keymap used as the minibuffer local keymap in the function `read-no-blanks-input'. By default, it makes the following bindings, in addition to those of `minibuffer-local-map': SPC `exit-minibuffer' TAB `exit-minibuffer' `?' `self-insert-and-exit' File: lispref.info, Node: Object from Minibuffer, Next: Minibuffer History, Prev: Text from Minibuffer, Up: Minibuffers Reading Lisp Objects with the Minibuffer ======================================== This section describes functions for reading Lisp objects with the minibuffer. - Function: read-minibuffer PROMPT &optional INITIAL This function reads a Lisp object in the minibuffer and returns it, without evaluating it. The arguments PROMPT and INITIAL are used as in `read-from-minibuffer'. This is a simplified interface to the `read-from-minibuffer' function: (read-minibuffer PROMPT INITIAL) == (read-from-minibuffer PROMPT INITIAL nil t) Here is an example in which we supply the string `"(testing)"' as initial input: (read-minibuffer "Enter an expression: " (format "%s" '(testing))) ;; Here is how the minibuffer is displayed: ---------- Buffer: Minibuffer ---------- Enter an expression: (testing)-!- ---------- Buffer: Minibuffer ---------- The user can type RET immediately to use the initial input as a default, or can edit the input. - Function: eval-minibuffer PROMPT &optional INITIAL This function reads a Lisp expression in the minibuffer, evaluates it, then returns the result. The arguments PROMPT and INITIAL are used as in `read-from-minibuffer'. This function simply evaluates the result of a call to `read-minibuffer': (eval-minibuffer PROMPT INITIAL) == (eval (read-minibuffer PROMPT INITIAL)) - Function: edit-and-eval-command PROMPT FORM This function reads a Lisp expression in the minibuffer, and then evaluates it. The difference between this command and `eval-minibuffer' is that here the initial FORM is not optional and it is treated as a Lisp object to be converted to printed representation rather than as a string of text. It is printed with `prin1', so if it is a string, double-quote characters (`"') appear in the initial text. *Note Output Functions::. The first thing `edit-and-eval-command' does is to activate the minibuffer with PROMPT as the prompt. Then it inserts the printed representation of FORM in the minibuffer, and lets the user edit. When the user exits the minibuffer, the edited text is read with `read' and then evaluated. The resulting value becomes the value of `edit-and-eval-command'. In the following example, we offer the user an expression with initial text which is a valid form already: (edit-and-eval-command "Please edit: " '(forward-word 1)) ;; After evaluation of the preceding expression, ;; the following appears in the minibuffer: ---------- Buffer: Minibuffer ---------- Please edit: (forward-word 1)-!- ---------- Buffer: Minibuffer ---------- Typing RET right away would exit the minibuffer and evaluate the expression, thus moving point forward one word. `edit-and-eval-command' returns `nil' in this example. File: lispref.info, Node: Minibuffer History, Next: Completion, Prev: Object from Minibuffer, Up: Minibuffers Minibuffer History ================== A "minibuffer history list" records previous minibuffer inputs so the user can reuse them conveniently. A history list is actually a symbol, not a list; it is a variable whose value is a list of strings (previous inputs), most recent first. There are many separate history lists, used for different kinds of inputs. It's the Lisp programmer's job to specify the right history list for each use of the minibuffer. The basic minibuffer input functions `read-from-minibuffer' and `completing-read' both accept an optional argument named HIST which is how you specify the history list. Here are the possible values: VARIABLE Use VARIABLE (a symbol) as the history list. (VARIABLE . STARTPOS) Use VARIABLE (a symbol) as the history list, and assume that the initial history position is STARTPOS (an integer, counting from zero which specifies the most recent element of the history). If you specify STARTPOS, then you should also specify that element of the history as the initial minibuffer contents, for consistency. If you don't specify HIST, then the default history list `minibuffer-history' is used. For other standard history lists, see below. You can also create your own history list variable; just initialize it to `nil' before the first use. Both `read-from-minibuffer' and `completing-read' add new elements to the history list automatically, and provide commands to allow the user to reuse items on the list. The only thing your program needs to do to use a history list is to initialize it and to pass its name to the input functions when you wish. But it is safe to modify the list by hand when the minibuffer input functions are not using it. - Variable: minibuffer-history The default history list for minibuffer history input. - Variable: query-replace-history A history list for arguments to `query-replace' (and similar arguments to other commands). - Variable: file-name-history A history list for file name arguments. - Variable: regexp-history A history list for regular expression arguments. - Variable: extended-command-history A history list for arguments that are names of extended commands. - Variable: shell-command-history A history list for arguments that are shell commands. - Variable: read-expression-history A history list for arguments that are Lisp expressions to evaluate. File: lispref.info, Node: Completion, Next: Yes-or-No Queries, Prev: Minibuffer History, Up: Minibuffers Completion ========== "Completion" is a feature that fills in the rest of a name starting from an abbreviation for it. Completion works by comparing the user's input against a list of valid names and determining how much of the name is determined uniquely by what the user has typed. For example, when you type `C-x b' (`switch-to-buffer') and then type the first few letters of the name of the buffer to which you wish to switch, and then type TAB (`minibuffer-complete'), Emacs extends the name as far as it can. Standard XEmacs commands offer completion for names of symbols, files, buffers, and processes; with the functions in this section, you can implement completion for other kinds of names. The `try-completion' function is the basic primitive for completion: it returns the longest determined completion of a given initial string, with a given set of strings to match against. The function `completing-read' provides a higher-level interface for completion. A call to `completing-read' specifies how to determine the list of valid names. The function then activates the minibuffer with a local keymap that binds a few keys to commands useful for completion. Other functions provide convenient simple interfaces for reading certain kinds of names with completion. * Menu: * Basic Completion:: Low-level functions for completing strings. (These are too low level to use the minibuffer.) * Minibuffer Completion:: Invoking the minibuffer with completion. * Completion Commands:: Minibuffer commands that do completion. * High-Level Completion:: Convenient special cases of completion (reading buffer name, file name, etc.) * Reading File Names:: Using completion to read file names. * Programmed Completion:: Finding the completions for a given file name. File: lispref.info, Node: Basic Completion, Next: Minibuffer Completion, Up: Completion Basic Completion Functions -------------------------- The two functions `try-completion' and `all-completions' have nothing in themselves to do with minibuffers. We describe them in this chapter so as to keep them near the higher-level completion features that do use the minibuffer. - Function: try-completion STRING COLLECTION &optional PREDICATE This function returns the longest common substring of all possible completions of STRING in COLLECTION. The value of COLLECTION must be an alist, an obarray, or a function that implements a virtual set of strings (see below). Completion compares STRING against each of the permissible completions specified by COLLECTION; if the beginning of the permissible completion equals STRING, it matches. If no permissible completions match, `try-completion' returns `nil'. If only one permissible completion matches, and the match is exact, then `try-completion' returns `t'. Otherwise, the value is the longest initial sequence common to all the permissible completions that match. If COLLECTION is an alist (*note Association Lists::.), the CARs of the alist elements form the set of permissible completions. If COLLECTION is an obarray (*note Creating Symbols::.), the names of all symbols in the obarray form the set of permissible completions. The global variable `obarray' holds an obarray containing the names of all interned Lisp symbols. Note that the only valid way to make a new obarray is to create it empty and then add symbols to it one by one using `intern'. Also, you cannot intern a given symbol in more than one obarray. If the argument PREDICATE is non-`nil', then it must be a function of one argument. It is used to test each possible match, and the match is accepted only if PREDICATE returns non-`nil'. The argument given to PREDICATE is either a cons cell from the alist (the CAR of which is a string) or else it is a symbol (*not* a symbol name) from the obarray. You can also use a symbol that is a function as COLLECTION. Then the function is solely responsible for performing completion; `try-completion' returns whatever this function returns. The function is called with three arguments: STRING, PREDICATE and `nil'. (The reason for the third argument is so that the same function can be used in `all-completions' and do the appropriate thing in either case.) *Note Programmed Completion::. In the first of the following examples, the string `foo' is matched by three of the alist CARs. All of the matches begin with the characters `fooba', so that is the result. In the second example, there is only one possible match, and it is exact, so the value is `t'. (try-completion "foo" '(("foobar1" 1) ("barfoo" 2) ("foobaz" 3) ("foobar2" 4))) => "fooba" (try-completion "foo" '(("barfoo" 2) ("foo" 3))) => t In the following example, numerous symbols begin with the characters `forw', and all of them begin with the word `forward'. In most of the symbols, this is followed with a `-', but not in all, so no more than `forward' can be completed. (try-completion "forw" obarray) => "forward" Finally, in the following example, only two of the three possible matches pass the predicate `test' (the string `foobaz' is too short). Both of those begin with the string `foobar'. (defun test (s) (> (length (car s)) 6)) => test (try-completion "foo" '(("foobar1" 1) ("barfoo" 2) ("foobaz" 3) ("foobar2" 4)) 'test) => "foobar" - Function: all-completions STRING COLLECTION &optional PREDICATE NOSPACE This function returns a list of all possible completions of STRING. The parameters to this function are the same as to `try-completion'. If COLLECTION is a function, it is called with three arguments: STRING, PREDICATE and `t'; then `all-completions' returns whatever the function returns. *Note Programmed Completion::. If NOSPACE is non-`nil', completions that start with a space are ignored unless STRING also starts with a space. Here is an example, using the function `test' shown in the example for `try-completion': (defun test (s) (> (length (car s)) 6)) => test (all-completions "foo" '(("foobar1" 1) ("barfoo" 2) ("foobaz" 3) ("foobar2" 4)) 'test) => ("foobar1" "foobar2") - Variable: completion-ignore-case If the value of this variable is non-`nil', XEmacs does not consider case significant in completion.