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;;; completion.el --- dynamic word-completion code

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;; Maintainer: FSF
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;; Keywords: abbrev
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;;; Commentary:

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;;; This is a Completion system for GNU Emacs
;;;
;;;  E-Mail: 
;;;   Internet: completion@think.com, bug-completion@think.com
;;;   UUCP: {rutgers,harvard,mit-eddie}!think!completion
;;;
;;;    If you are a new user, we'd appreciate knowing your site name and
;;; any comments you have.
;;;
;;;
;;;				NO WARRANTY
;;;
;;; This software is distributed free of charge and is in the public domain.
;;; Anyone may use, duplicate or modify this program.  Thinking Machines
;;; Corporation does not restrict in any way the use of this software by
;;; anyone.
;;; 
;;; Thinking Machines Corporation provides absolutely no warranty of any kind.
;;; The entire risk as to the quality and performance of this program is with
;;; you.  In no event will Thinking Machines Corporation be liable to you for
;;; damages, including any lost profits, lost monies, or other special,
;;; incidental or consequential damages arising out of the use of this program.
;;;
;;; You must not restrict the distribution of this software.
;;;
;;; Please keep this notice and author information in any copies you make.
;;;
;;; 4/90
;;;
;;;
;;; Advertisement
;;;---------------
;;;  Try using this.  If you are like most you will be happy you did.
;;; 
;;; What to put in .emacs
;;;-----------------------
;;; (load "completion") ;; If it's not part of the standard band.
;;; (initialize-completions)
;;; 
;;; For best results, be sure to byte-compile the file first.
;;;

;;; Authors 
;;;---------
;;;     Jim Salem      {salem@think.com}
;;;     Brewster Kahle {brewster@think.com}
;;;  Thinking Machines Corporation
;;;  245 First St., Cambridge MA 02142 (617) 876-1111
;;;
;;; Mailing Lists
;;;---------------
;;;
;;; Bugs to bug-completion@think.com
;;; Comments to completion@think.com
;;; Requests to be added completion-request@think.com
;;;
;;; Availability
;;;--------------
;;; Anonymous FTP from think.com
;;;

;;;---------------------------------------------------------------------------
;;; Documentation [Slightly out of date]
;;;---------------------------------------------------------------------------
;;;  (also check the documentation string of the functions)
;;;
;;; Introduction
;;;---------------
;;;  
;;;     After you type a few characters, pressing the "complete" key inserts
;;; the rest of the word you are likely to type.  
;;;
;;; This watches all the words that you type and remembers them.  When 
;;; typing a new word, pressing "complete" (meta-return) "completes" the
;;; word by inserting the most recently used word that begins with the 
;;; same characters.  If you press meta-return repeatedly, it cycles
;;; through all the words it knows about.
;;;
;;;  If you like the completion then just continue typing, it is as if you
;;; entered the text by hand.  If you want the inserted extra characters 
;;; to go away, type control-w or delete.  More options are described below.
;;;
;;;  The guesses are made in the order of the most recently "used".  Typing
;;; in a word and then typing a separator character (such as a space) "uses" 
;;; the word.  So does moving a cursor over the word.  If no words are found, 
;;; it uses an extended version of the dabbrev style completion.
;;;
;;;   You automatically save the completions you use to a file between 
;;; sessions.  
;;;
;;;   Completion enables programmers to enter longer, more descriptive 
;;; variable names while typing fewer keystrokes than they normally would.
;;;
;;;
;;; Full documentation
;;;---------------------
;;;
;;;   A "word" is any string containing characters with either word or symbol 
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;;; syntax.  [E.G. Any alphanumeric string with hyphens, underscores, etc.]
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;;; Unless you change the constants, you must type at least three characters
;;; for the word to be recognized.  Only words longer than 6 characters are
;;; saved.
;;;
;;;   When you load this file, completion will be on.  I suggest you use the
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;;; compiled version (because it is noticeably faster).
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;;;
;;;  M-X completion-mode toggles whether or not new words are added to the
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;;; database by changing the value of enable-completion.
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;;;
;;;  SAVING/LOADING COMPLETIONS
;;;   Completions are automatically saved from one session to another
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;;; (unless save-completions-flag or enable-completion is nil).
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;;; Loading this file (or calling initialize-completions) causes EMACS
;;; to load a completions database for a saved completions file 
;;; (default: ~/.completions).  When you exit, EMACS saves a copy of the
;;; completions that you 
;;; often use.  When you next start, EMACS loads in the saved completion file.
;;;
;;;   The number of completions saved depends loosely on 
;;; *saved-completions-decay-factor*.  Completions that have never been 
;;; inserted via "complete" are not saved.  You are encouraged to experiment
;;; with different functions (see compute-completion-min-num-uses).
;;;
;;;   Some completions are permanent and are always saved out.  These 
;;; completions have their num-uses slot set to T.  Use 
;;; add-permanent-completion to do this
;;;
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;;;   Completions are saved only if enable-completion is T.  The number of old
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;;; versions kept of the saved completions file is controlled by 
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;;; completions-file-versions-kept.
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;;;
;;; COMPLETE KEY OPTIONS
;;;   The complete function takes a numeric arguments.  
;;;  control-u :: leave the point at the beginning of the completion rather 
;;;               than the middle.
;;;  a number  :: rotate through the possible completions by that amount
;;;  `-'       :: same as -1 (insert previous completion)
;;;
;;; HOW THE DATABASE IS MAINTAINED
;;;  <write>
;;;
;;; UPDATING THE DATABASE MANUALLY
;;;   m-x kill-completion 
;;;     kills the completion at point.
;;;   m-x add-completion
;;;   m-x add-permanent-completion
;;;   
;;; UPDATING THE DATABASE FROM A SOURCE CODE FILE
;;;   m-x add-completions-from-buffer
;;;     Parses all the definition names from a C or LISP mode buffer and
;;;     adds them to the completion database.
;;;
;;;   m-x add-completions-from-lisp-file 
;;;     Parses all the definition names from a C or Lisp mode file and
;;;     adds them to the completion database.
;;;
;;; UPDATING THE DATABASE FROM A TAGS TABLE
;;;   m-x add-completions-from-tags-table
;;;     Adds completions from the current tags-table-buffer.
;;;
;;; HOW A COMPLETION IS FOUND
;;;  <write>
;;;
;;; STRING CASING
;;;   Completion is string case independent if case-fold-search has its 
;;;  normal default of T.  Also when the completion is inserted the case of the
;;;  entry is coerced appropriately.  
;;;  [E.G.  APP --> APPROPRIATELY     app --> appropriately  
;;;         App --> Appropriately]
;;;
;;; INITIALIZATION
;;;  The form `(initialize-completions)' initializes the completion system by 
;;; trying to load in the user's completions.  After the first cal, further 
;;; calls have no effect so one should be careful not to put the form in a 
;;; site's standard site-init file.
;;;
;;;---------------------------------------------------------------------------
;;;
;;;

;;;---------------------------------------------------------------------------
;;; Functions you might like to call
;;;---------------------------------------------------------------------------
;;;
;;;  add-completion  string &optional num-uses
;;;    Adds a new string to the database
;;;
;;;  add-permanent-completion  string
;;;    Adds a new string to the database with num-uses = T
;;;

;;;  kill-completion string
;;;    Kills the completion from the database.
;;;
;;;  clear-all-completions
;;;    Clears the database
;;;
;;;  list-all-completions
;;;    Returns a list of all completions.
;;;
;;;
;;;  next-completion string &optional index
;;;    Returns a completion entry that starts with string.
;;;
;;;  find-exact-completion string
;;;    Returns a completion entry that exactly matches string.
;;;
;;;  complete
;;;    Inserts a completion at point
;;;
;;;  initialize-completions
;;;    Loads the completions file and sets up so that exiting emacs will 
;;;  save them.
;;;
;;;  save-completions-to-file &optional filename  
;;;  load-completions-from-file &optional filename
;;;
;;;-----------------------------------------------
;;; Other functions
;;;-----------------------------------------------
;;;
;;;  get-completion-list string
;;;
;;; These things are for manipulating the structure
;;;  make-completion string num-uses
;;;  completion-num-uses completion 
;;;  completion-string completion
;;;  set-completion-num-uses completion num-uses
;;;  set-completion-string completion string
;;;  
;;;

;;;-----------------------------------------------
;;; To Do :: (anybody ?)
;;;-----------------------------------------------
;;;
;;;   Implement Lookup and keyboard interface in C
;;;   Add package prefix smarts (for Common Lisp)
;;;   Add autoprompting of possible completions after every keystroke (fast
;;;      terminals only !)
;;;   Add doc. to texinfo
;;;
;;;
;;;-----------------------------------------------
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;;; Change Log:
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;;;-----------------------------------------------
;;;    Sometime in '84 Brewster implemented a somewhat buggy version for 
;;; Symbolics LISPMs.
;;;    Jan. '85 Jim became enamored of the idea and implemented a faster, 
;;; more robust version.
;;;    With input from many users at TMC, (rose, craig, and gls come to mind),
;;; the current style of interface was developed. 
;;;    9/87, Jim and Brewster took terminals home.  Yuck.  After 
;;; complaining for a while Brewester implemented a subset of the current 
;;; LISPM version for GNU Emacs.  
;;;    8/88  After complaining for a while (and with sufficient 
;;; promised rewards), Jim reimplemented a version of GNU completion
;;; superior to that of the LISPM version.
;;;
;;;-----------------------------------------------
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;;; Acknowledgements
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;;;-----------------------------------------------
;;;  Cliff Lasser (cal@think.com), Kevin Herbert (kph@cisco.com),
;;;  eero@media-lab, kgk@cs.brown.edu, jla@ai.mit.edu,
;;;
;;;-----------------------------------------------
;;; Change Log
;;;-----------------------------------------------
;;; From version 9 to 10
;;;  - Allowance for non-integral *completion-version* nos.
;;;  - Fix cmpl-apply-as-top-level for keyboard macros
;;;  - Fix broken completion merging (in save-completions-to-file)
;;;  - More misc. fixes for version 19.0 of emacs
;;;
;;; From Version 8 to 9
;;;  - Ported to version 19.0 of emacs (backcompatible with version 18)
;;;  - Added add-completions-from-tags-table (with thanks to eero@media-lab)
;;;
;;; From Version 7 to 8
;;;  - Misc. changes to comments
;;;  - new completion key bindings: c-x o, M->, M-<, c-a, c-e
;;;  - cdabbrev now checks all the visible window buffers and the "other buffer"
;;;  - `%' is now a symbol character rather than a separator (except in C mode)
;;;
;;; From Version 6 to 7
;;;  - Fixed bug with saving out .completion file the first time
;;;
;;; From Version 5 to 6
;;;  - removed statistics recording
;;;  - reworked advise to handle autoloads
;;;  - Fixed fortran mode support
;;;  - Added new cursor motion triggers
;;;
;;; From Version 4 to 5
;;;  - doesn't bother saving if nothing has changed
;;;  - auto-save if haven't used for a 1/2 hour
;;;  - save period extended to two weeks
;;;  - minor fix to capitalization code
;;;  - added *completion-auto-save-period* to variables recorded.
;;;  - added reenter protection to cmpl-record-statistics-filter
;;;  - added backup protection to save-completions-to-file (prevents 
;;;    problems with disk full errors)

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;;; Code:

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;;;---------------------------------------------------------------------------
;;; User changeable parameters
;;;---------------------------------------------------------------------------

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(defvar enable-completion t
  "*Non-nil means enable recording and saving of completions.
If nil, no new words added to the database or saved to the init file.")
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(defvar save-completions-flag t
  "*Non-nil means save most-used completions when exiting Emacs.
See also `saved-completions-retention-time'.")
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(defvar save-completions-file-name "~/.completions"
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  "*The filename to save completions to.")

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(defvar save-completions-retention-time 336
  "*Discard a completion if unused for this many hours.
\(1 day = 24, 1 week = 168).  If this is 0, non-permanent completions
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will not be saved unless these are used.  Default is two weeks.")
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(defvar completion-on-separator-character nil
  "*Non-nil means separator characters mark previous word as used.
This means the word will be saved as a completion.")
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(defvar completions-file-versions-kept kept-new-versions
  "*Number of versions to keep for the saved completions file.")
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(defvar completion-prompt-speed-threshold 4800
  "*Minimum output speed at which to display next potential completion.")
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(defvar completion-cdabbrev-prompt-flag nil
  "*If non-nil, the next completion prompt does a cdabbrev search.
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This can be time consuming.")

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(defvar completion-search-distance 15000
  "*How far to search in the buffer when looking for completions.
In number of characters.  If nil, search the whole buffer.")
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(defvar completions-merging-modes '(lisp c)
  "*List of modes {`c' or `lisp'} for automatic completions merging.
Definitions from visited files which have these modes
are automatically added to the completion database.")
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;;;(defvar *record-cmpl-statistics-p* nil
;;;  "*If non-nil, record completion statistics.")
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;;;(defvar *completion-auto-save-period* 1800
;;;  "*The period in seconds to wait for emacs to be idle before autosaving
;;;the completions.  Default is a 1/2 hour.")
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(defconst completion-min-length nil ;; defined below in eval-when
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  "*The minimum length of a stored completion.
DON'T CHANGE WITHOUT RECOMPILING !  This is used by macros.")

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(defconst completion-max-length nil ;; defined below in eval-when
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  "*The maximum length of a stored completion.
DON'T CHANGE WITHOUT RECOMPILING !  This is used by macros.")

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(defconst completion-prefix-min-length nil ;; defined below in eval-when
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  "The minimum length of a completion search string.
DON'T CHANGE WITHOUT RECOMPILING !  This is used by macros.")

(defmacro eval-when-compile-load-eval (&rest body)
  ;; eval everything before expanding
  (mapcar 'eval body)
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  (cons 'progn body))
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(defun completion-eval-when ()
  (eval-when-compile-load-eval
   ;; These vars. are defined at both compile and load time.
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   (setq completion-min-length 6)
   (setq completion-max-length 200)
   (setq completion-prefix-min-length 3)))
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(completion-eval-when)
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;; Need this file around too
(require 'cl)
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;;;---------------------------------------------------------------------------
;;; Internal Variables
;;;---------------------------------------------------------------------------

(defvar cmpl-initialized-p nil
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  "Set to t when the completion system is initialized.
Indicates that the old completion file has been read in.")
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(defvar cmpl-completions-accepted-p nil
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  "Set to t as soon as the first completion has been accepted.
Used to decide whether to save completions.")
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;;;---------------------------------------------------------------------------
;;; Low level tools
;;;---------------------------------------------------------------------------

;;;-----------------------------------------------
;;; Misc.
;;;-----------------------------------------------

(defun minibuffer-window-selected-p ()
  "True iff the current window is the minibuffer."
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  (window-minibuffer-p (selected-window)))
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(defmacro cmpl-read-time-eval (form)
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  ;; Like the #. reader macro
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  (eval form))
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;;;-----------------------------------------------
;;; String case coercion
;;;-----------------------------------------------

(defun cmpl-string-case-type (string)
  "Returns :capitalized, :up, :down, :mixed, or :neither."
  (let ((case-fold-search nil))
    (cond ((string-match "[a-z]" string)
	   (cond ((string-match "[A-Z]" string)
		  (cond ((and (> (length string) 1)
			      (null (string-match "[A-Z]" string 1)))
			 ':capitalized)
			(t
			 ':mixed)))
		 (t ':down)))
	  (t
	   (cond ((string-match "[A-Z]" string)
		  ':up)
		 (t ':neither))))
    ))

;;; Tests -
;;; (cmpl-string-case-type "123ABCDEF456") --> :up
;;; (cmpl-string-case-type "123abcdef456") --> :down
;;; (cmpl-string-case-type "123aBcDeF456") --> :mixed
;;; (cmpl-string-case-type "123456")       --> :neither
;;; (cmpl-string-case-type "Abcde123")     --> :capitalized

(defun cmpl-coerce-string-case (string case-type)
  (cond ((eq case-type ':down) (downcase string))
	((eq case-type ':up) (upcase string))
	((eq case-type ':capitalized)
	 (setq string (downcase string))
	 (aset string 0 (logand ?\337 (aref string 0)))
	 string)
	(t string)
	))

(defun cmpl-merge-string-cases (string-to-coerce given-string)
  (let ((string-case-type (cmpl-string-case-type string-to-coerce))
	)
    (cond ((memq string-case-type '(:down :up :capitalized))
	   ;; Found string is in a standard case.  Coerce to a type based on
	   ;; the given string
	   (cmpl-coerce-string-case string-to-coerce
			       (cmpl-string-case-type given-string))
	   )
	  (t
	   ;; If the found string is in some unusual case, just insert it
	   ;; as is
	   string-to-coerce)
	  )))

;;; Tests -
;;; (cmpl-merge-string-cases "AbCdEf456" "abc")     --> AbCdEf456
;;; (cmpl-merge-string-cases "abcdef456" "ABC")     --> ABCDEF456
;;; (cmpl-merge-string-cases "ABCDEF456" "Abc")     --> Abcdef456
;;; (cmpl-merge-string-cases "ABCDEF456" "abc")     --> abcdef456


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(defun cmpl-hours-since-origin ()
  (let ((time (current-time)))
    (+ (* (/ (car time) 3600.0) (lsh 1 16))
       (/ (nth 2 time) 3600.0))))
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;;;---------------------------------------------------------------------------
;;; "Symbol" parsing functions
;;;---------------------------------------------------------------------------
;;; The functions symbol-before-point, symbol-under-point, etc. quickly return
;;; an appropriate symbol string.  The strategy is to temporarily change
;;; the syntax table to enable fast symbol searching.  There are three classes
;;; of syntax in these "symbol" syntax tables ::
;;;
;;; syntax (?_) - "symbol" chars (e.g. alphanumerics)
;;; syntax (?w) - symbol chars to ignore at end of words (e.g. period).  
;;; syntax (? ) - everything else
;;;
;;; Thus by judicious use of scan-sexps and forward-word, we can get
;;; the word we want relatively fast and without consing.  
;;;
;;; Why do we need a separate category for "symbol chars to ignore at ends" ?
;;; For example, in LISP we want starting :'s trimmed 
;;; so keyword argument specifiers also define the keyword completion.  And,
;;; for example, in C we want `.' appearing in a structure ref. to
;;; be kept intact in order to store the whole structure ref.; however, if 
;;; it appears at the end of a symbol it should be discarded because it is
;;; probably used as a period.

;;; Here is the default completion syntax ::
;;; Symbol chars :: A-Z a-z 0-9 @ / \ * + ~ $ < > %
;;; Symbol chars to ignore at ends :: _ : . -
;;; Separator chars. :: <tab> <space> ! ^ & ( ) = ` | { } [ ] ; " ' #
;;;                     , ? <Everything else>

;;; Mode specific differences and notes ::
;;;  LISP diffs ->
;;;    Symbol chars :: ! & ? = ^
;;;
;;; C diffs ->
;;;   Separator chars :: + * / : %
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;;;  A note on the hyphen (`-').  Perhaps the hyphen should also be a separator
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;;; char., however, we wanted to have completion symbols include pointer 
;;; references.  For example, "foo->bar" is a symbol as far as completion is
;;; concerned.
;;;
;;; FORTRAN diffs ->
;;;   Separator chars :: + - * / :
;;;
;;; Pathname diffs ->
;;;   Symbol chars :: .
;;;  Of course there is no pathname "mode" and in fact we have not implemented
;;; this table.  However, if there was such a mode, this is what it would look
;;; like.

;;;-----------------------------------------------
;;; Table definitions
;;;-----------------------------------------------

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(defun cmpl-make-standard-completion-syntax-table ()
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  (let ((table (make-vector 256 0)) ;; default syntax is whitespace
	)
    ;; alpha chars
    (dotimes (i 26)
      (modify-syntax-entry (+ ?a i) "_" table)
      (modify-syntax-entry (+ ?A i) "_" table))
    ;; digit chars.
    (dotimes (i 10)
      (modify-syntax-entry (+ ?0 i) "_" table))
    ;; Other ones
    (let ((symbol-chars '(?@ ?/ ?\\ ?* ?+ ?~ ?$ ?< ?> ?%))
	  (symbol-chars-ignore '(?_ ?- ?: ?.))
	  )
      (dolist (char symbol-chars)
	(modify-syntax-entry char "_" table))
      (dolist (char symbol-chars-ignore)
	(modify-syntax-entry char "w" table)
	)
      )
    table))

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(defconst cmpl-standard-syntax-table (cmpl-make-standard-completion-syntax-table))
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(defun cmpl-make-lisp-completion-syntax-table ()
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  (let ((table (copy-syntax-table cmpl-standard-syntax-table))
	(symbol-chars '(?! ?& ?? ?= ?^))
	)
    (dolist (char symbol-chars)
      (modify-syntax-entry char "_" table))
    table))
	   
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(defun cmpl-make-c-completion-syntax-table ()
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  (let ((table (copy-syntax-table cmpl-standard-syntax-table))
	(separator-chars '(?+ ?* ?/ ?: ?%))
	)
    (dolist (char separator-chars)
      (modify-syntax-entry char " " table))
    table))

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(defun cmpl-make-fortran-completion-syntax-table ()
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  (let ((table (copy-syntax-table cmpl-standard-syntax-table))
	(separator-chars '(?+ ?- ?* ?/ ?:))
	)
    (dolist (char separator-chars)
      (modify-syntax-entry char " " table))
    table))

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(defconst cmpl-lisp-syntax-table       (cmpl-make-lisp-completion-syntax-table))
(defconst cmpl-c-syntax-table          (cmpl-make-c-completion-syntax-table))
(defconst cmpl-fortran-syntax-table    (cmpl-make-fortran-completion-syntax-table))
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(defvar cmpl-syntax-table cmpl-standard-syntax-table
  "This variable holds the current completion syntax table.")
(make-variable-buffer-local 'cmpl-syntax-table)

;;;-----------------------------------------------
;;; Installing the appropriate mode tables
;;;-----------------------------------------------

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(add-hook 'lisp-mode-hook
	  '(lambda ()
	     (setq cmpl-syntax-table cmpl-lisp-syntax-table)))
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(add-hook 'c-mode-hook
	  '(lambda ()
	     (setq cmpl-syntax-table cmpl-c-syntax-table)))
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(add-hook 'fortran-mode-hook
	  '(lambda ()
	     (setq cmpl-syntax-table cmpl-fortran-syntax-table)
	     (completion-setup-fortran-mode)))
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;;;-----------------------------------------------
;;; Symbol functions
;;;-----------------------------------------------
(defvar cmpl-symbol-start nil
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  "Holds first character of symbol, after any completion symbol function.")
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(defvar cmpl-symbol-end nil
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  "Holds last character of symbol, after any completion symbol function.")
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;;; These are temp. vars. we use to avoid using let.
;;;   Why ?  Small speed improvement.
(defvar cmpl-saved-syntax nil)
(defvar cmpl-saved-point nil)

(defun symbol-under-point ()
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  "Returns the symbol that the point is currently on.
But only if it is longer than `completion-min-length'."
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  (setq cmpl-saved-syntax (syntax-table))
  (set-syntax-table cmpl-syntax-table)
  (cond 
  ;; Cursor is on following-char and after preceding-char
    ((memq (char-syntax (following-char)) '(?w ?_))     
     (setq cmpl-saved-point (point)
	   cmpl-symbol-start (scan-sexps (1+ cmpl-saved-point) -1)
	   cmpl-symbol-end (scan-sexps cmpl-saved-point 1))
     ;; remove chars to ignore at the start
     (cond ((= (char-syntax (char-after cmpl-symbol-start)) ?w)
	    (goto-char cmpl-symbol-start)
	    (forward-word 1)
	    (setq cmpl-symbol-start (point))
	    (goto-char cmpl-saved-point)
	    ))
     ;; remove chars to ignore at the end
     (cond ((= (char-syntax (char-after (1- cmpl-symbol-end))) ?w)
	    (goto-char cmpl-symbol-end)
	    (forward-word -1)
	    (setq cmpl-symbol-end (point))
	    (goto-char cmpl-saved-point)
	    ))
     ;; restore state
     (set-syntax-table cmpl-saved-syntax)
     ;; Return completion if the length is reasonable
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     (if (and (<= (cmpl-read-time-eval completion-min-length)
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		  (- cmpl-symbol-end cmpl-symbol-start))
	      (<= (- cmpl-symbol-end cmpl-symbol-start)
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		  (cmpl-read-time-eval completion-max-length)))
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	 (buffer-substring cmpl-symbol-start cmpl-symbol-end))
     )
    (t 
     ;; restore table if no symbol
     (set-syntax-table cmpl-saved-syntax)
     nil)
    ))

;;; tests for symbol-under-point
;;;  `^' indicates cursor pos. where value is returned
;;;  simple-word-test
;;;  ^^^^^^^^^^^^^^^^  --> simple-word-test
;;;  _harder_word_test_
;;;  ^^^^^^^^^^^^^^^^^^ --> harder_word_test
;;;  .___.______.
;;;  --> nil
;;;  /foo/bar/quux.hello
;;;  ^^^^^^^^^^^^^^^^^^^ --> /foo/bar/quux.hello
;;;

(defun symbol-before-point ()
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  "Returns a string of the symbol immediately before point.
Returns nil if there isn't one longer than `completion-min-length'."       
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  ;; This is called when a word separator is typed so it must be FAST !
  (setq cmpl-saved-syntax (syntax-table))
  (set-syntax-table cmpl-syntax-table)
  ;; Cursor is on following-char and after preceding-char
  (cond ((= (setq cmpl-preceding-syntax (char-syntax (preceding-char))) ?_)
	 ;; No chars. to ignore at end
	 (setq cmpl-symbol-end (point)
	       cmpl-symbol-start (scan-sexps (1+ cmpl-symbol-end) -1)
	       )
	 ;; remove chars to ignore at the start
	 (cond ((= (char-syntax (char-after cmpl-symbol-start)) ?w)
		(goto-char cmpl-symbol-start)
		(forward-word 1)
		(setq cmpl-symbol-start (point))
		(goto-char cmpl-symbol-end)
		))
	 ;; restore state
	 (set-syntax-table cmpl-saved-syntax)
	 ;; return value if long enough
	 (if (>= cmpl-symbol-end
		 (+ cmpl-symbol-start
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		    (cmpl-read-time-eval completion-min-length)))
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	     (buffer-substring cmpl-symbol-start cmpl-symbol-end))
	 )
	((= cmpl-preceding-syntax ?w)
	 ;; chars to ignore at end
	 (setq cmpl-saved-point (point)
	       cmpl-symbol-start (scan-sexps (1+ cmpl-saved-point) -1))
	 ;; take off chars. from end
	 (forward-word -1)
	 (setq cmpl-symbol-end (point))
	 ;; remove chars to ignore at the start
	 (cond ((= (char-syntax (char-after cmpl-symbol-start)) ?w)
		(goto-char cmpl-symbol-start)
		(forward-word 1)
		(setq cmpl-symbol-start (point))
		))
	 ;; restore state
	 (goto-char cmpl-saved-point)
	 (set-syntax-table cmpl-saved-syntax)
	 ;; Return completion if the length is reasonable
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	 (if (and (<= (cmpl-read-time-eval completion-min-length)
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		      (- cmpl-symbol-end cmpl-symbol-start))
		  (<= (- cmpl-symbol-end cmpl-symbol-start)
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		      (cmpl-read-time-eval completion-max-length)))
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	     (buffer-substring cmpl-symbol-start cmpl-symbol-end))
	 )
	(t 
	 ;; restore table if no symbol
	 (set-syntax-table cmpl-saved-syntax)
	 nil)
	))

;;; tests for symbol-before-point
;;;  `^' indicates cursor pos. where value is returned
;;;  simple-word-test
;;;  ^ --> nil
;;;   ^ --> nil
;;;          ^  --> simple-w
;;;                  ^ --> simple-word-test
;;;  _harder_word_test_
;;;                   ^  --> harder_word_test
;;;                    ^  --> harder_word_test
;;;          ^ --> harder
;;;  .___....
;;;  --> nil

(defun symbol-under-or-before-point ()
  ;;; This could be made slightly faster but it is better to avoid
  ;;; copying all the code.
  ;;; However, it is only used by the completion string prompter.
  ;;; If it comes into common use, it could be rewritten.
  (setq cmpl-saved-syntax (syntax-table))
  (set-syntax-table cmpl-syntax-table)
  (cond ((memq (char-syntax (following-char)) '(?w ?_))
	 (set-syntax-table cmpl-saved-syntax)
	 (symbol-under-point))
	(t
	 (set-syntax-table cmpl-saved-syntax)
	 (symbol-before-point))
	))


(defun symbol-before-point-for-complete ()
  ;; "Returns a string of the symbol immediately before point
  ;; or nil if there isn't one.  Like symbol-before-point but doesn't trim the
  ;; end chars."
  ;; Cursor is on following-char and after preceding-char
  (setq cmpl-saved-syntax (syntax-table))
  (set-syntax-table cmpl-syntax-table)
  (cond ((memq (setq cmpl-preceding-syntax (char-syntax (preceding-char)))
	       '(?_ ?w))
	 (setq cmpl-symbol-end (point)
	       cmpl-symbol-start (scan-sexps (1+ cmpl-symbol-end) -1)
	       )
	 ;; remove chars to ignore at the start
	 (cond ((= (char-syntax (char-after cmpl-symbol-start)) ?w)
		(goto-char cmpl-symbol-start)
		(forward-word 1)
		(setq cmpl-symbol-start (point))
		(goto-char cmpl-symbol-end)
		))
	 ;; restore state
	 (set-syntax-table cmpl-saved-syntax)
	 ;; Return completion if the length is reasonable
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	 (if (and (<= (cmpl-read-time-eval
		       completion-prefix-min-length)
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		      (- cmpl-symbol-end cmpl-symbol-start))
		  (<= (- cmpl-symbol-end cmpl-symbol-start)
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		      (cmpl-read-time-eval completion-max-length)))
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	     (buffer-substring cmpl-symbol-start cmpl-symbol-end))
	 )
	(t 
	 ;; restore table if no symbol
	 (set-syntax-table cmpl-saved-syntax)
	 nil)
	))

;;; tests for symbol-before-point-for-complete
;;;  `^' indicates cursor pos. where value is returned
;;;  simple-word-test
;;;  ^ --> nil
;;;   ^ --> nil
;;;          ^  --> simple-w
;;;                  ^ --> simple-word-test
;;;  _harder_word_test_
;;;                   ^  --> harder_word_test
;;;                    ^  --> harder_word_test_
;;;          ^ --> harder_
;;;  .___....
;;;  --> nil



;;;---------------------------------------------------------------------------
;;; Statistics Recording
;;;---------------------------------------------------------------------------

;;; Note that the guts of this has been turned off.  The guts
;;; are in completion-stats.el.

;;;-----------------------------------------------
;;; Conditionalizing code on *record-cmpl-statistics-p*
;;;-----------------------------------------------
;;; All statistics code outside this block should use this
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(defmacro cmpl-statistics-block (&rest body))
;;;  "Only executes body if we are recording statistics."
;;;  (list 'cond
;;;	(list* '*record-cmpl-statistics-p* body)
;;;	))		 
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;;;-----------------------------------------------
;;; Completion Sources
;;;-----------------------------------------------

;; ID numbers
(defconst cmpl-source-unknown 0)
(defconst cmpl-source-init-file 1)
(defconst cmpl-source-file-parsing 2)
(defconst cmpl-source-separator 3)
(defconst cmpl-source-cursor-moves 4)
(defconst cmpl-source-interactive 5)
(defconst cmpl-source-cdabbrev 6)
(defconst num-cmpl-sources 7)
(defvar current-completion-source cmpl-source-unknown)



;;;---------------------------------------------------------------------------
;;; Completion Method #2: dabbrev-expand style
;;;---------------------------------------------------------------------------
;;;
;;;   This method is used if there are no useful stored completions.  It is 
;;; based on dabbrev-expand with these differences :
;;;   1) Faster (we don't use regexps)
;;;   2) case coercion handled correctly
;;; This is called cdabbrev to differentiate it.
;;;   We simply search backwards through the file looking for words which
;;; start with the same letters we are trying to complete.
;;;

(defvar cdabbrev-completions-tried nil)
;;;  "A list of all the cdabbrev completions since the last reset.")

(defvar cdabbrev-current-point 0)
;;;  "The current point position the cdabbrev search is at.")

(defvar cdabbrev-current-window nil)
;;;  "The current window we are looking for cdabbrevs in.  T if looking in
;;; (other-buffer), NIL if no more  cdabbrevs.")

(defvar cdabbrev-wrapped-p nil)
;;;  "T if the cdabbrev search has wrapped around the file.")

(defvar cdabbrev-abbrev-string "")
(defvar cdabbrev-start-point 0)

;;; Test strings for cdabbrev
;;; cdat-upcase   ;;same namestring
;;; CDAT-UPCASE   ;;ok
;;; cdat2         ;;too short
;;; cdat-1-2-3-4  ;;ok
;;; a-cdat-1      ;;doesn't start correctly
;;; cdat-simple   ;;ok


(defun reset-cdabbrev (abbrev-string &optional initial-completions-tried)
  "Resets the cdabbrev search to search for abbrev-string.
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INITIAL-COMPLETIONS-TRIED is a list of downcased strings to ignore
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during the search."
  (setq cdabbrev-abbrev-string abbrev-string
	cdabbrev-completions-tried
	(cons (downcase abbrev-string) initial-completions-tried)
	)
  (reset-cdabbrev-window t)
  )

(defun set-cdabbrev-buffer ()
  ;; cdabbrev-current-window must not be NIL
  (set-buffer (if (eq cdabbrev-current-window t)
		  (other-buffer)
		  (window-buffer cdabbrev-current-window)))
  )


(defun reset-cdabbrev-window (&optional initializep)
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  "Resets the cdabbrev search to search for abbrev-string."
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  ;; Set the window
  (cond (initializep
	 (setq cdabbrev-current-window (selected-window))
	 )
	((eq cdabbrev-current-window t)
	 ;; Everything has failed
	 (setq cdabbrev-current-window nil))
	(cdabbrev-current-window
	 (setq cdabbrev-current-window (next-window cdabbrev-current-window))
	 (if (eq cdabbrev-current-window (selected-window))
	     ;; No more windows, try other buffer.
	     (setq cdabbrev-current-window t)))
	)
  (when cdabbrev-current-window
    (save-excursion
      (set-cdabbrev-buffer)
      (setq cdabbrev-current-point (point)
	    cdabbrev-start-point cdabbrev-current-point
	    cdabbrev-stop-point
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	    (if completion-search-distance
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		(max (point-min)
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		     (- cdabbrev-start-point completion-search-distance))
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		(point-min))
	    cdabbrev-wrapped-p nil)
      )))

(defun next-cdabbrev ()
  "Return the next possible cdabbrev expansion or nil if there isn't one.
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`reset-cdabbrev' must've been called already.
This is sensitive to `case-fold-search'."
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  ;; note that case-fold-search affects the behavior of this function
  ;; Bug: won't pick up an expansion that starts at the top of buffer
  (when cdabbrev-current-window
    (let (saved-point 
	  saved-syntax
	  (expansion nil)
	  downcase-expansion tried-list syntax saved-point-2)
      (save-excursion
	(unwind-protect
	    (progn
	      ;; Switch to current completion buffer
	      (set-cdabbrev-buffer)
	      ;; Save current buffer state
	      (setq saved-point  (point)
		    saved-syntax (syntax-table))
	      ;; Restore completion state
	      (set-syntax-table cmpl-syntax-table)
	      (goto-char cdabbrev-current-point)
	      ;; Loop looking for completions
	      (while
		  ;; This code returns t if it should loop again
		  (cond
		    (;; search for the string
		     (search-backward cdabbrev-abbrev-string cdabbrev-stop-point t)
		     ;; return nil if the completion is valid
		     (not
		      (and
		       ;; does it start with a separator char ?
		       (or (= (setq syntax (char-syntax (preceding-char))) ? )
			   (and (= syntax ?w)
				;; symbol char to ignore at end.  Are we at end ?
				(progn
				  (setq saved-point-2 (point))
				  (forward-word -1)
				  (prog1
				    (= (char-syntax (preceding-char)) ? )
				    (goto-char saved-point-2)
				    ))))
		       ;; is the symbol long enough ?
		       (setq expansion (symbol-under-point))
		       ;; have we not tried this one before
		       (progn
			 ;; See if we've already used it
			 (setq tried-list cdabbrev-completions-tried
			       downcase-expansion (downcase expansion))
			 (while (and tried-list
				     (not (string-equal downcase-expansion
							(car tried-list))))
			   ;; Already tried, don't choose this one
			   (setq tried-list (cdr tried-list))
			   )
			 ;; at this point tried-list will be nil if this
			 ;; expansion has not yet been tried
			 (if tried-list
			     (setq expansion nil)
			     t)
			 ))))
		    ;; search failed
		    (cdabbrev-wrapped-p
		     ;; If already wrapped, then we've failed completely
		     nil)
		    (t
		     ;; need to wrap
		     (goto-char (setq cdabbrev-current-point
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				      (if completion-search-distance
					  (min (point-max) (+ cdabbrev-start-point completion-search-distance))
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					  (point-max))))
		
		     (setq cdabbrev-wrapped-p t))
		    ))
	      ;; end of while loop
	      (cond (expansion
		     ;; successful
		     (setq cdabbrev-completions-tried
			   (cons downcase-expansion cdabbrev-completions-tried)
			   cdabbrev-current-point (point))))
	      )
	  (set-syntax-table saved-syntax)
	  (goto-char saved-point)
	  ))
      ;; If no expansion, go to next window
      (cond (expansion)
	    (t (reset-cdabbrev-window)
	       (next-cdabbrev)))
      )))

;;; The following must be eval'd in the minibuffer ::
;;; (reset-cdabbrev "cdat")
;;; (next-cdabbrev)  --> "cdat-simple"
;;; (next-cdabbrev)  --> "cdat-1-2-3-4"
;;; (next-cdabbrev)  --> "CDAT-UPCASE"
;;; (next-cdabbrev)  --> "cdat-wrapping"
;;; (next-cdabbrev)  --> "cdat_start_sym"
;;; (next-cdabbrev)  --> nil
;;; (next-cdabbrev)  --> nil
;;; (next-cdabbrev)  --> nil

;;; _cdat_start_sym
;;; cdat-wrapping


;;;---------------------------------------------------------------------------
;;; Completion Database
;;;---------------------------------------------------------------------------

;;; We use two storage modes for the two search types ::
;;;  1) Prefix {cmpl-prefix-obarray} for looking up possible completions
;;;      Used by search-completion-next
;;;      the value of the symbol is nil or a cons of head and tail pointers
;;;  2) Interning {cmpl-obarray} to see if it's in the database
;;;      Used by find-exact-completion, completion-in-database-p
;;;      The value of the symbol is the completion entry

;;; bad things may happen if this length is changed due to the way
;;; GNU implements obarrays
(defconst cmpl-obarray-length 511)

(defvar cmpl-prefix-obarray (make-vector cmpl-obarray-length 0)
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  "An obarray used to store the downcased completion prefixes.
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Each symbol is bound to a list of completion entries.")

(defvar cmpl-obarray (make-vector cmpl-obarray-length 0)
  "An obarray used to store the downcased completions.
Each symbol is bound to a single completion entry.")

;;;-----------------------------------------------
;;; Completion Entry Structure Definition
;;;-----------------------------------------------

;;; A completion entry is a LIST of string, prefix-symbol num-uses, and
;;; last-use-time (the time the completion was last used)
;;; last-use-time is T if the string should be kept permanently
;;; num-uses is incremented everytime the completion is used.

;;; We chose lists because (car foo) is faster than (aref foo 0) and the 
;;; creation time is about the same.

;;; READER MACROS

(defmacro completion-string (completion-entry)
  (list 'car completion-entry))

(defmacro completion-num-uses (completion-entry)
  ;;  "The number of times it has used.  Used to decide whether to save 
  ;; it."
  (list 'car (list 'cdr completion-entry)))

(defmacro completion-last-use-time (completion-entry)
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  ;;  "The time it was last used.  In hours since origin.  Used to decide
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  ;; whether to save it.  T if one should always save it."
  (list 'nth 2 completion-entry))

(defmacro completion-source (completion-entry)
  (list 'nth 3 completion-entry))

;;; WRITER MACROS
(defmacro set-completion-string (completion-entry string)
  (list 'setcar completion-entry string))

(defmacro set-completion-num-uses (completion-entry num-uses)
  (list 'setcar (list 'cdr completion-entry) num-uses))

(defmacro set-completion-last-use-time (completion-entry last-use-time)
  (list 'setcar (list 'cdr (list 'cdr completion-entry)) last-use-time))

;;; CONSTRUCTOR
(defun make-completion (string)
  "Returns a list of a completion entry."
  (list (list string 0 nil current-completion-source)))

;; Obsolete
;;(defmacro cmpl-prefix-entry-symbol (completion-entry)
;;  (list 'car (list 'cdr completion-entry)))



;;;-----------------------------------------------
;;; Prefix symbol entry definition
;;;-----------------------------------------------
;;; A cons of (head . tail)

;;; READER Macros

(defmacro cmpl-prefix-entry-head (prefix-entry)
  (list 'car prefix-entry))

(defmacro cmpl-prefix-entry-tail (prefix-entry)
  (list 'cdr prefix-entry))

;;; WRITER Macros

(defmacro set-cmpl-prefix-entry-head (prefix-entry new-head)
  (list 'setcar prefix-entry new-head))

(defmacro set-cmpl-prefix-entry-tail (prefix-entry new-tail)
  (list 'setcdr prefix-entry new-tail))

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;;; Constructor
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(defun make-cmpl-prefix-entry (completion-entry-list)
  "Makes a new prefix entry containing only completion-entry."
  (cons completion-entry-list completion-entry-list))

;;;-----------------------------------------------
;;; Completion Database - Utilities
;;;-----------------------------------------------

(defun clear-all-completions ()
  "Initializes the completion storage.  All existing completions are lost."
  (interactive)
  (setq cmpl-prefix-obarray (make-vector cmpl-obarray-length 0))
  (setq cmpl-obarray (make-vector cmpl-obarray-length 0))
  (cmpl-statistics-block
    (record-clear-all-completions))
  )

(defun list-all-completions ()
  "Returns a list of all the known completion entries."
  (let ((return-completions nil))
    (mapatoms 'list-all-completions-1 cmpl-prefix-obarray)
    return-completions))

(defun list-all-completions-1 (prefix-symbol)
  (if (boundp prefix-symbol)
      (setq return-completions
	    (append (cmpl-prefix-entry-head (symbol-value prefix-symbol))
		    return-completions))))

(defun list-all-completions-by-hash-bucket ()
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  "Return list of lists of known completion entries, organized by hash bucket."
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  (let ((return-completions nil))
    (mapatoms 'list-all-completions-by-hash-bucket-1 cmpl-prefix-obarray)
    return-completions))

(defun list-all-completions-by-hash-bucket-1 (prefix-symbol)
  (if (boundp prefix-symbol)
      (setq return-completions
	    (cons (cmpl-prefix-entry-head (symbol-value prefix-symbol))
		  return-completions))))


;;;-----------------------------------------------
;;; Updating the database
;;;-----------------------------------------------
;;;
;;;   These are the internal functions used to update the datebase
;;;
;;;
(defvar completion-to-accept nil)
  ;;"Set to a string that is pending its acceptance."
  ;; this checked by the top level reading functions

(defvar cmpl-db-downcase-string nil)
  ;; "Setup by find-exact-completion, etc.  The given string, downcased."
(defvar cmpl-db-symbol nil)
  ;; "The interned symbol corresponding to cmpl-db-downcase-string.
  ;; Set up by cmpl-db-symbol."
(defvar cmpl-db-prefix-symbol nil)
  ;; "The interned prefix symbol corresponding to cmpl-db-downcase-string."
(defvar cmpl-db-entry nil)
(defvar cmpl-db-debug-p nil
  "Set to T if you want to debug the database.")

;;; READS
(defun find-exact-completion (string)
  "Returns the completion entry for string or nil.
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Sets up `cmpl-db-downcase-string' and `cmpl-db-symbol'."
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  (and (boundp (setq cmpl-db-symbol
		     (intern (setq cmpl-db-downcase-string (downcase string))
			     cmpl-obarray)))
       (symbol-value cmpl-db-symbol)
       ))

(defun find-cmpl-prefix-entry (prefix-string)
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  "Returns the prefix entry for string.
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Sets `cmpl-db-prefix-symbol'.
Prefix-string must be exactly `completion-prefix-min-length' long
and downcased.  Sets up `cmpl-db-prefix-symbol'."
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  (and (boundp (setq cmpl-db-prefix-symbol
		     (intern prefix-string cmpl-prefix-obarray)))
       (symbol-value cmpl-db-prefix-symbol)))

(defvar inside-locate-completion-entry nil)
;; used to trap lossage in silent error correction

(defun locate-completion-entry (completion-entry prefix-entry)
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  "Locates the completion entry.
Returns a pointer to the element before the completion entry or nil if
the completion entry is at the head.
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Must be called after `find-exact-completion'."
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  (let ((prefix-list (cmpl-prefix-entry-head prefix-entry))
	 next-prefix-list
	 )
    (cond
      ((not (eq (car prefix-list) completion-entry))
       ;; not already at head
       (while (and prefix-list
		   (not (eq completion-entry
			    (car (setq next-prefix-list (cdr prefix-list)))
			    )))
	 (setq prefix-list next-prefix-list))
       (cond (;; found
	      prefix-list)
	     ;; Didn't find it.  Database is messed up.
	     (cmpl-db-debug-p
	      ;; not found, error if debug mode
	      (error "Completion entry exists but not on prefix list - %s"
		     string))
	     (inside-locate-completion-entry
	      ;; recursive error: really scrod
	      (locate-completion-db-error))
	     (t
	       ;; Patch out
	       (set cmpl-db-symbol nil)
	       ;; Retry
	       (locate-completion-entry-retry completion-entry)
	       ))))))

(defun locate-completion-entry-retry (old-entry)
  (let ((inside-locate-completion-entry t))
    (add-completion (completion-string old-entry)
		    (completion-num-uses old-entry)
		    (completion-last-use-time old-entry))
    (let ((cmpl-entry (find-exact-completion (completion-string old-entry)))
	  (pref-entry
	   (if cmpl-entry
	       (find-cmpl-prefix-entry
		 (substring cmpl-db-downcase-string
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			    0 completion-prefix-min-length))))
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	  )
      (if (and cmpl-entry pref-entry)
	  ;; try again
	  (locate-completion-entry cmpl-entry pref-entry)
	  ;; still losing
	  (locate-completion-db-error))
      )))

(defun locate-completion-db-error ()
  ;; recursive error: really scrod
  (error "Completion database corrupted.  Try M-x clear-all-completions.  Send bug report.")
  )

;;; WRITES
(defun add-completion-to-tail-if-new (string)
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  "If STRING is not in the database add it to appropriate prefix list.
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STRING is added to the end of the appropriate prefix list with
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num-uses = 0.  The database is unchanged if it is there.  STRING must be
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longer than `completion-prefix-min-length'.
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This must be very fast.
Returns the completion entry."
  (or (find-exact-completion string)
      ;; not there
      (let (;; create an entry
	    (entry (make-completion string))
	    ;; setup the prefix
	    (prefix-entry (find-cmpl-prefix-entry
			    (substring cmpl-db-downcase-string 0
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				       (cmpl-read-time-eval
					completion-prefix-min-length))))
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	    )
	;; The next two forms should happen as a unit (atomically) but
	;; no fatal errors should result if that is not the case.
	(cond (prefix-entry
	       ;; These two should be atomic, but nothing fatal will happen
	       ;; if they're not.
	       (setcdr (cmpl-prefix-entry-tail prefix-entry) entry)
	       (set-cmpl-prefix-entry-tail prefix-entry entry))
	      (t
	       (set cmpl-db-prefix-symbol (make-cmpl-prefix-entry entry))
	       ))
	;; statistics
	(cmpl-statistics-block
	  (note-added-completion))
	;; set symbol
	(set cmpl-db-symbol (car entry))
	)))

(defun add-completion-to-head (string)
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  "If STRING is not in the database, add it to prefix list.
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STRING is added to the head of the appropriate prefix list.  Otherwise
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it is moved to the head of the list.
STRING must be longer than `completion-prefix-min-length'.
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Updates the saved string with the supplied string.
This must be very fast.
Returns the completion entry."
  ;; Handle pending acceptance
  (if completion-to-accept (accept-completion))
  ;; test if already in database
  (if (setq cmpl-db-entry (find-exact-completion string))
      ;; found
      (let* ((prefix-entry (find-cmpl-prefix-entry
			     (substring cmpl-db-downcase-string 0
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					(cmpl-read-time-eval
					 completion-prefix-min-length))))
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	     (splice-ptr (locate-completion-entry cmpl-db-entry prefix-entry))
	     (cmpl-ptr (cdr splice-ptr))
	     )
	;; update entry
	(set-completion-string cmpl-db-entry string)
	;; move to head (if necessary)
	(cond (splice-ptr
	       ;; These should all execute atomically but it is not fatal if
	       ;; they don't.
	       ;; splice it out
	       (or (setcdr splice-ptr (cdr cmpl-ptr))
		   ;; fix up tail if necessary
		   (set-cmpl-prefix-entry-tail prefix-entry splice-ptr))
	       ;; splice in at head
	       (setcdr cmpl-ptr (cmpl-prefix-entry-head prefix-entry))
	       (set-cmpl-prefix-entry-head prefix-entry cmpl-ptr)
	       ))
	cmpl-db-entry)
    ;; not there
    (let (;; create an entry
	  (entry (make-completion string))
	  ;; setup the prefix
	  (prefix-entry (find-cmpl-prefix-entry
			  (substring cmpl-db-downcase-string 0
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				     (cmpl-read-time-eval
				      completion-prefix-min-length))))
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	  )
      (cond (prefix-entry
	     ;; Splice in at head
	     (setcdr entry (cmpl-prefix-entry-head prefix-entry))
	     (set-cmpl-prefix-entry-head prefix-entry entry))
	    (t
	     ;; Start new prefix entry
	     (set cmpl-db-prefix-symbol (make-cmpl-prefix-entry entry))
	     ))
      ;; statistics
      (cmpl-statistics-block
	(note-added-completion))
      ;; Add it to the symbol
      (set cmpl-db-symbol (car entry))
      )))
      
(defun delete-completion (string)
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  "Deletes the completion from the database.
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String must be longer than `completion-prefix-min-length'."
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  ;; Handle pending acceptance
  (if completion-to-accept (accept-completion))
  (if (setq cmpl-db-entry (find-exact-completion string))
      ;; found
      (let* ((prefix-entry (find-cmpl-prefix-entry 
			     (substring cmpl-db-downcase-string 0
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					(cmpl-read-time-eval
					 completion-prefix-min-length))))
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	     (splice-ptr (locate-completion-entry cmpl-db-entry prefix-entry))
	     )
	 ;; delete symbol reference
	 (set cmpl-db-symbol nil)
	 ;; remove from prefix list
	 (cond (splice-ptr
		;; not at head
		(or (setcdr splice-ptr (cdr (cdr splice-ptr)))
		    ;; fix up tail if necessary
		    (set-cmpl-prefix-entry-tail prefix-entry splice-ptr))
		)
	       (t
		;; at head
		(or (set-cmpl-prefix-entry-head
		      prefix-entry (cdr (cmpl-prefix-entry-head prefix-entry)))
		    ;; List is now empty
		    (set cmpl-db-prefix-symbol nil))
		))
	 (cmpl-statistics-block
	   (note-completion-deleted))
	 )
      (error "Unknown completion: %s.  Couldn't delete it." string)
      ))

;;; Tests --
;;;  - Add and Find -
;;; (add-completion-to-head "banana")     --> ("banana" 0 nil 0)
;;; (find-exact-completion "banana")      --> ("banana" 0 nil 0)
;;; (find-exact-completion "bana")        --> nil
;;; (car (find-cmpl-prefix-entry "ban"))  --> (("banana" ...))
;;; (cdr (find-cmpl-prefix-entry "ban"))  --> (("banana" ...))
;;; (add-completion-to-head "banish")     --> ("banish" 0 nil 0)
;;; (find-exact-completion "banish")      --> ("banish" 0 nil 0)
;;; (car (find-cmpl-prefix-entry "ban"))  --> (("banish" ...) ("banana" ...))
;;; (cdr (find-cmpl-prefix-entry "ban"))  --> (("banana" ...))
;;; (add-completion-to-head "banana")     --> ("banana" 0 nil 0)
;;; (car (find-cmpl-prefix-entry "ban"))  --> (("banana" ...) ("banish" ...))
;;; (cdr (find-cmpl-prefix-entry "ban"))  --> (("banish" ...))
;;;
;;;  - Deleting -
;;; (add-completion-to-head "banner")     --> ("banner" 0 nil 0)
;;; (delete-completion "banner")        
;;; (find-exact-completion "banner")      --> nil
;;; (car (find-cmpl-prefix-entry "ban"))  --> (("banana" ...) ("banish" ...))
;;; (cdr (find-cmpl-prefix-entry "ban"))  --> (("banish" ...))
;;; (add-completion-to-head "banner")     --> ("banner" 0 nil 0) 
;;; (delete-completion "banana")        
;;; (car (find-cmpl-prefix-entry "ban"))  --> (("banner" ...) ("banish" ...))
;;; (cdr (find-cmpl-prefix-entry "ban"))  --> (("banish" ...))
;;; (delete-completion "banner")        
;;; (delete-completion "banish")                 
;;; (find-cmpl-prefix-entry "ban")        --> nil
;;; (delete-completion "banner")          --> error
;;;
;;; - Tail -
;;; (add-completion-to-tail-if-new "banana") --> ("banana" 0 nil 0)
;;; (car (find-cmpl-prefix-entry "ban"))     --> (("banana" ...))
;;; (cdr (find-cmpl-prefix-entry "ban"))     --> (("banana" ...))
;;; (add-completion-to-tail-if-new "banish") --> ("banish" 0 nil 0)
;;; (car (find-cmpl-prefix-entry "ban"))     -->(("banana" ...) ("banish" ...))
;;; (cdr (find-cmpl-prefix-entry "ban"))     -->(("banish" ...))
;;;


;;;---------------------------------------------------------------------------
;;; Database Update :: Interface level routines
;;;---------------------------------------------------------------------------
;;; 
;;; These lie on top of the database ref. functions but below the standard
;;; user interface level


(defun interactive-completion-string-reader (prompt)
  (let* ((default (symbol-under-or-before-point))
	 (new-prompt
	  (if default
	      (format "%s: (default: %s) " prompt default)
	      (format "%s: " prompt))
	   )
	 (read (completing-read new-prompt cmpl-obarray))
	 )
    (if (zerop (length read)) (setq read (or default "")))
    (list read)
    ))

(defun check-completion-length (string)
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  (if (< (length string) completion-min-length)
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      (error "The string \"%s\" is too short to be saved as a completion."
	     string)
      (list string)))

(defun add-completion (string &optional num-uses last-use-time)
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  "Add STRING to completion list, or move it to head of list.
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The completion is altered appropriately if num-uses and/or last-use-time is 
specified."
  (interactive (interactive-completion-string-reader "Completion to add"))
  (check-completion-length string)
  (let* ((current-completion-source (if (interactive-p)
					cmpl-source-interactive
					current-completion-source))
	 (entry (add-completion-to-head string)))
    
    (if num-uses (set-completion-num-uses entry num-uses))
    (if last-use-time
	(set-completion-last-use-time entry last-use-time))
    ))

(defun add-permanent-completion (string)
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  "Add STRING if it isn't already listed, and mark it permanent."
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  (interactive
    (interactive-completion-string-reader "Completion to add permanently"))
  (let ((current-completion-source (if (interactive-p)
				       cmpl-source-interactive
				       current-completion-source))
	)
    (add-completion string nil t)
    ))

(defun kill-completion (string)
  (interactive (interactive-completion-string-reader "Completion to kill"))
  (check-completion-length string)
  (delete-completion string)
  )

(defun accept-completion ()
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  "Accepts the pending completion in `completion-to-accept'.
This bumps num-uses.  Called by `add-completion-to-head' and 
`completion-search-reset'."
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  (let ((string completion-to-accept)
	;; if this is added afresh here, then it must be a cdabbrev
	(current-completion-source cmpl-source-cdabbrev)
	entry
	)
    (setq completion-to-accept nil)
    (setq entry (add-completion-to-head string))
    (set-completion-num-uses entry (1+ (completion-num-uses entry)))
    (setq cmpl-completions-accepted-p t)
    ))

(defun use-completion-under-point ()
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  "Add the completion symbol underneath the point into the completion buffer."
  (let ((string (and enable-completion (symbol-under-point)))
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	(current-completion-source cmpl-source-cursor-moves))
    (if string (add-completion-to-head string))))
	
(defun use-completion-before-point ()
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  "Add the completion symbol before point into the completion buffer."
  (let ((string (and enable-completion (symbol-before-point)))
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	(current-completion-source cmpl-source-cursor-moves))
    (if string (add-completion-to-head string))))

(defun use-completion-under-or-before-point ()
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  "Add the completion symbol before point into the completion buffer."
  (let ((string (and enable-completion (symbol-under-or-before-point)))
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	(current-completion-source cmpl-source-cursor-moves))
    (if string (add-completion-to-head string))))

(defun use-completion-before-separator ()
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  "Add the completion symbol before point into the completion buffer.
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Completions added this way will automatically be saved if
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`completion-on-separator-character' is non-nil."
  (let ((string (and enable-completion (symbol-before-point)))
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	(current-completion-source cmpl-source-separator)
	entry)
    (cmpl-statistics-block
      (note-separator-character string)
      )
    (cond (string
	   (setq entry (add-completion-to-head string))
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	   (when (and completion-on-separator-character
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		      (zerop (completion-num-uses entry)))
	     (set-completion-num-uses entry 1)
	     (setq cmpl-completions-accepted-p t)
	     )))
    ))

;;; Tests --
;;;  - Add and Find -
;;; (add-completion "banana" 5 10)  
;;; (find-exact-completion "banana")  --> ("banana" 5 10 0)
;;; (add-completion "banana" 6)     
;;; (find-exact-completion "banana")  --> ("banana" 6 10 0)
;;; (add-completion "banish")
;;; (car (find-cmpl-prefix-entry "ban"))  --> (("banish" ...) ("banana" ...))
;;;
;;;  - Accepting -
;;; (setq completion-to-accept "banana")
;;; (accept-completion)                   
;;; (find-exact-completion "banana")      --> ("banana" 7 10)
;;; (car (find-cmpl-prefix-entry "ban"))  --> (("banana" ...) ("banish" ...))
;;; (setq completion-to-accept "banish")
;;; (add-completion "banner")           
;;; (car (find-cmpl-prefix-entry "ban"))
;;;        --> (("banner" ...) ("banish" 1 ...) ("banana" 7 ...))
;;;
;;;  - Deleting -
;;; (kill-completion "banish")          
;;; (car (find-cmpl-prefix-entry "ban"))  --> (("banner" ...) ("banana" ...))


;;;---------------------------------------------------------------------------
;;; Searching the database
;;;---------------------------------------------------------------------------
;;; Functions outside this block must call completion-search-reset followed
;;; by calls to completion-search-next or completion-search-peek
;;;

;;; Status variables
;; Commented out to improve loading speed
(defvar cmpl-test-string "")
;;  "The current string used by completion-search-next."
(defvar cmpl-test-regexp "")
;;  "The current regexp used by completion-search-next. 
;;   (derived from cmpl-test-string)"
(defvar cmpl-last-index 0)
;;  "The last index that completion-search-next was called with."
(defvar cmpl-cdabbrev-reset-p nil)
;;  "Set to t when cdabbrevs have been reset."
(defvar cmpl-next-possibilities nil)
;;   "A pointer to the element BEFORE the next set of possible completions.
;;  cadr of this is the cmpl-next-possibility"
(defvar cmpl-starting-possibilities nil)
;;  "The initial list of starting possibilities."
(defvar cmpl-next-possibility nil)
;;   "The cached next possibility."
(defvar cmpl-tried-list nil)
;;   "A downcased list of all the completions we have tried."


(defun completion-search-reset (string)
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  "Set up the for completion searching for STRING.
STRING must be longer than `completion-prefix-min-length'."
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  (if completion-to-accept (accept-completion))
  (setq cmpl-starting-possibilities
	(cmpl-prefix-entry-head
	  (find-cmpl-prefix-entry (downcase (substring string 0 3))))
	cmpl-test-string string
	cmpl-test-regexp (concat (regexp-quote string) "."))
  (completion-search-reset-1)
  )

(defun completion-search-reset-1 ()
  (setq cmpl-next-possibilities cmpl-starting-possibilities
	cmpl-next-possibility   nil
	cmpl-cdabbrev-reset-p nil
	cmpl-last-index -1
	cmpl-tried-list nil
	))

(defun completion-search-next (index)
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  "Return the next completion entry.
If INDEX is out of sequence, reset and start from the top.
If there are no more entries, try cdabbrev and returns only a string."
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  (cond
    ((= index (setq cmpl-last-index (1+ cmpl-last-index)))
     (completion-search-peek t))
    ((minusp index)
     (completion-search-reset-1)
     (setq cmpl-last-index index)
     ;; reverse the possibilities list
     (setq cmpl-next-possibilities (reverse cmpl-starting-possibilities))
     ;; do a "normal" search
     (while (and (completion-search-peek nil)
		 (minusp (setq index (1+ index))))
       (setq cmpl-next-possibility nil)
       )
     (cond ((not cmpl-next-possibilities))
	    ;; If no more possibilities, leave it that way
	   ((= -1 cmpl-last-index)
	    ;; next completion is at index 0.  reset next-possibility list 
	    ;; to start at beginning
	    (setq cmpl-next-possibilities cmpl-starting-possibilities))
	   (t
	    ;; otherwise point to one before current
	    (setq cmpl-next-possibilities
		  (nthcdr (- (length cmpl-starting-possibilities)
			     (length cmpl-next-possibilities))
			  cmpl-starting-possibilities))
	    )))
    (t
     ;; non-negative index, reset and search
     ;;(prin1 'reset)
     (completion-search-reset-1)
     (setq cmpl-last-index index)
     (while (and (completion-search-peek t)
		 (not (minusp (setq index (1- index)))))
       (setq cmpl-next-possibility nil)
       ))
    )
  (prog1
      cmpl-next-possibility
    (setq cmpl-next-possibility nil)
    ))
      

(defun completion-search-peek (use-cdabbrev)
  "Returns the next completion entry without actually moving the pointers.
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Calling this again or calling `completion-search-next' results in the same 
string being returned.  Depends on `case-fold-search'.
If there are no more entries, try cdabbrev and then return only a string."
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  (cond
    ;; return the cached value if we have it
    (cmpl-next-possibility)
    ((and cmpl-next-possibilities
	  ;; still a few possibilities left
	  (progn
	    (while
		(and (not (eq 0 (string-match cmpl-test-regexp
					      (completion-string (car cmpl-next-possibilities)))))
		     (setq cmpl-next-possibilities (cdr cmpl-next-possibilities))
		     ))
	    cmpl-next-possibilities
	    ))
     ;; successful match
     (setq cmpl-next-possibility (car cmpl-next-possibilities)
	   cmpl-tried-list (cons (downcase (completion-string cmpl-next-possibility))
				 cmpl-tried-list)
	   cmpl-next-possibilities (cdr cmpl-next-possibilities)
	   )
     cmpl-next-possibility)
    (use-cdabbrev
     ;; unsuccessful, use cdabbrev
     (cond ((not cmpl-cdabbrev-reset-p)
	    (reset-cdabbrev cmpl-test-string cmpl-tried-list)
	    (setq cmpl-cdabbrev-reset-p t)
	    ))
     (setq cmpl-next-possibility (next-cdabbrev))
     )
    ;; Completely unsuccessful, return nil
    ))

;;; Tests --
;;;  - Add and Find -
;;; (add-completion "banana")       
;;; (completion-search-reset "ban")  
;;; (completion-search-next 0)        --> "banana"
;;;
;;;  - Discrimination -
;;; (add-completion "cumberland")       
;;; (add-completion "cumberbund")       
;;; cumbering   
;;; (completion-search-reset "cumb")
;;; (completion-search-peek t)        --> "cumberbund"
;;; (completion-search-next 0)        --> "cumberbund"
;;; (completion-search-peek t)        --> "cumberland"
;;; (completion-search-next 1)        --> "cumberland"
;;; (completion-search-peek nil)      --> nil
;;; (completion-search-next 2)        --> "cumbering"  {cdabbrev}
;;; (completion-search-next 3)        -->  nil or "cumming"{depends on context}
;;; (completion-search-next 1)        --> "cumberland"
;;; (completion-search-peek t)        --> "cumbering"  {cdabbrev}
;;;
;;;  - Accepting -
;;; (completion-search-next 1)        --> "cumberland"
;;; (setq completion-to-accept "cumberland")
;;; (completion-search-reset "foo")
;;; (completion-search-reset "cum")
;;; (completion-search-next 0)        --> "cumberland"
;;;
;;;  - Deleting -
;;; (kill-completion "cumberland")
;;; cummings    
;;; (completion-search-reset "cum")
;;; (completion-search-next 0)        --> "cumberbund"
;;; (completion-search-next 1)        --> "cummings"
;;;
;;;  - Ignoring Capitalization -
;;; (completion-search-reset "CuMb")
;;; (completion-search-next 0)            --> "cumberbund"



;;;-----------------------------------------------
;;; COMPLETE
;;;-----------------------------------------------

(defun completion-mode ()
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  "Toggles whether or not to add new words to the completion database."
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  (interactive)
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  (setq enable-completion (not enable-completion))
  (message "Completion mode is now %s." (if enable-completion "ON" "OFF"))
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  )
	
(defvar cmpl-current-index 0)
(defvar cmpl-original-string nil)
(defvar cmpl-last-insert-location -1)
(defvar cmpl-leave-point-at-start nil)

(defun complete (&optional arg)
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  "Fill out a completion of the word before point.  
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Point is left at end.  Consecutive calls rotate through all possibilities.
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Prefix args ::
  control-u :: leave the point at the beginning of the completion rather 
               than at the end.
  a number  :: rotate through the possible completions by that amount
  `-'       :: same as -1 (insert previous completion)
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 {See the comments at the top of `completion.el' for more info.}"
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  (interactive "*p")
  ;;; Set up variables
  (cond ((eq last-command this-command)
	 ;; Undo last one
	 (delete-region cmpl-last-insert-location (point))
	 ;; get next completion
	 (setq cmpl-current-index (+ cmpl-current-index (or arg 1)))
	 )
	(t
	 (if (not cmpl-initialized-p)
	     (initialize-completions)) ;; make sure everything's loaded
	 (cond ((consp current-prefix-arg) ;; control-u
		(setq arg 0)
		(setq cmpl-leave-point-at-start t)
		)
	       (t
		(setq cmpl-leave-point-at-start nil)
		))
	 ;; get string
	 (setq cmpl-original-string (symbol-before-point-for-complete))
	 (cond ((not cmpl-original-string)
		(setq this-command 'failed-complete)
		(error "To complete, the point must be after a symbol at least %d character long."
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		       completion-prefix-min-length)))
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	 ;; get index	     
	 (setq cmpl-current-index (if current-prefix-arg arg 0))
	 ;; statistics
	 (cmpl-statistics-block
	   (note-complete-entered-afresh cmpl-original-string))
	 ;; reset database
	 (completion-search-reset cmpl-original-string)
	 ;; erase what we've got
	 (delete-region cmpl-symbol-start cmpl-symbol-end)
	 ))

  ;; point is at the point to insert the new symbol
  ;; Get the next completion
  (let* ((print-status-p
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	  (and (>= baud-rate completion-prompt-speed-threshold)
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