root/trunk/lisp/textmodes/table.el

;;; table.el --- create and edit WYSIWYG text based embedded tables

;; Copyright (C) 2000, 2001, 2002, 2003, 2004,
;;   2005, 2006, 2007, 2008  Free Software Foundation, Inc.

;; Keywords: wp, convenience
;; Author: Takaaki Ota <Takaaki.Ota@am.sony.com>
;; Created: Sat Jul 08 2000 13:28:45 (PST)
;; Revised: Wed Jan 03 2007 13:23:46 (PST)

;; This file is part of GNU Emacs.

;; GNU Emacs is free software; you can redistribute it and/or modify
;; it under the terms of the GNU General Public License as published by
;; the Free Software Foundation; either version 3, or (at your option)
;; any later version.

;; GNU Emacs is distributed in the hope that it will be useful,
;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
;; GNU General Public License for more details.

;; You should have received a copy of the GNU General Public License
;; along with GNU Emacs; see the file COPYING.  If not, write to the
;; Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
;; Boston, MA 02110-1301, USA.

;;; Commentary:

;; -------------
;; Introduction:
;; -------------
;;
;; This package provides text based table creation and editing
;; feature.  With this package Emacs is capable of editing tables that
;; are embedded inside a text document, the feature similar to the
;; ones seen in modern WYSIWYG word processors.  A table is a
;; rectangular text area consisting from a surrounding frame and
;; content inside the frame.  The content is usually subdivided into
;; multiple rectangular cells, see the actual tables used below in
;; this document.  Once a table is recognized, editing operation
;; inside a table cell is confined into that specific cell's
;; rectangular area.  This means that typing and deleting characters
;; inside a cell do not affect any outside text but introduces
;; appropriate formatting only to the cell contents.  If necessary for
;; accommodating added text in the cell, the cell automatically grows
;; vertically and/or horizontally.  The package uses no major mode nor
;; minor mode for its implementation because the subject text is
;; localized within a buffer.  Therefore the special behaviors inside
;; a table cells are implemented by using keymap text property
;; instead of buffer wide mode-map.
;;
;;
;; -----------
;; Background:
;; -----------
;;
;; Paul Georgief is one of my best friends.  He became an Emacs
;; convert after I recommended him trying it several years ago.  Now
;; we both are devoted disciples of Emacsism and elisp cult.  One day
;; in his Emacs exploration he asked me "Tak, what is a command to
;; edit tables in Emacs?".  This question started my journey of this
;; table package development.  May the code be with me!  In the
;; software world Emacs is probably one of the longest lifetime record
;; holders.  Amazingly there have been no direct support for WYSIWYG
;; table editing tasks in Emacs.  Many people must have experienced
;; manipulating existing overwrite-mode and picture-mode for this task
;; and only dreamed of having such a lisp package which supports this
;; specific task directly.  Certainly, I have been one of them.  The
;; most difficult part of dealing with table editing in Emacs probably
;; is how to realize localized rectangular editing effect.  Emacs has
;; no rectangular narrowing mechanism.  Existing rect package provides
;; basically kill, delete and yank operations of a rectangle, which
;; internally is a mere list of strings.  A simple approach for
;; realizing the localized virtual rectangular operation is combining
;; rect package capability with a temporary buffer.  Insertion and
;; deletion of a character to a table cell can be trapped by a
;; function that copies the cell rectangle to a temporary buffer then
;; apply the insertion/deletion to the temporary contents.  Then it
;; formats the contents by filling the paragraphs in order to fit it
;; into the original rectangular area and finally copy it back to the
;; original buffer.  This simplistic approach has to bear with
;; significant performance hit.  As cell grows larger the copying
;; rectangle back and forth between the original buffer and the
;; temporary buffer becomes expensive and unbearably slow.  It was
;; completely impractical and an obvious failure.  An idea has been
;; borrowed from the original Emacs design to overcome this
;; shortcoming.  When the terminal screen update was slow and
;; expensive Emacs employed a clever algorithm to reduce actual screen
;; update by removing redundant redrawing operations.  Also the actual
;; redrawing was done only when there was enough idling time.  This
;; technique significantly improved the previously mentioned
;; undesirable situation.  Now the original buffer's rectangle is
;; copied into a cache buffer only once.  Any cell editing operation
;; is done only to the cache contents.  When there is enough idling
;; time the original buffer's rectangle is updated with the current
;; cache contents.  This delayed operation is implemented by using
;; Emacs's timer function.  To reduce the visual awkwardness
;; introduced by the delayed effect the cursor location is updated in
;; real-time as a user types while the cell contents remains the same
;; until the next idling time.  A key to the success of this approach
;; is how to maintain cache coherency.  As a user moves point in and
;; out of a cell the table buffer contents and the cache buffer
;; contents must be synchronized without a mistake.  By observing user
;; action carefully this is possible however not easy.  Once this
;; mechanism is firmly implemented the rest of table features grew in
;; relatively painless progression.  Those users who are familiar with
;; Emacs internals appreciate this table package more.  Because it
;; demonstrates how extensible Emacs is by showing something that
;; appears like a magic.  It lets you re-discover the potential of
;; Emacs.
;;
;;
;; -------------
;; Entry Points:
;; -------------
;;
;; If this is the first time for you to try this package, go ahead and
;; load the package by M-x `load-file' RET.  Specify the package file
;; name "table.el".  Then switch to a new test buffer and issue the
;; command M-x `table-insert' RET.  It'll ask you number of columns,
;; number of rows, cell width and cell height.  Give some small
;; numbers for each of them.  Play with the resulted table for a
;; while.  If you have menu system find the item "Table" under "Tools"
;; and "Table" in the menu bar when the point is in a table cell.
;; Some of them are pretty intuitive and you can easily guess what
;; they do.  M-x `describe-function' and get the documentation of
;; `table-insert'.  The document includes a short tutorial.  When you
;; are tired of guessing how it works come back to this document
;; again.
;;
;; To use the package regularly place this file in the site library
;; directory and add the next expression in your .emacs file.  Make
;; sure that directory is included in the `load-path'.
;;
;;   (require 'table)
;;
;; Have the next expression also, if you want always be ready to edit
;; tables inside text files.  This mechanism is analogous to
;; fontification in a sense that tables are recognized at editing time
;; without having table information saved along with the text itself.
;;
;;   (add-hook 'text-mode-hook 'table-recognize)
;;
;; Following is a table of entry points and brief description of each
;; of them.  The tables below are of course generated and edited by
;; using this package.  Not all the commands are bound to keys.  Many
;; of them must be invoked by "M-x" (`execute-extended-command')
;; command.  Refer to the section "Keymap" below for the commands
;; available from keys.
;;
;; +------------------------------------------------------------------+
;; |                    User Visible Entry Points                     |
;; +-------------------------------+----------------------------------+
;; |           Function            |           Description            |
;; +-------------------------------+----------------------------------+
;; |`table-insert'                 |Insert a table consisting of grid |
;; |                               |of cells by specifying the number |
;; |                               |of COLUMNS, number of ROWS, cell  |
;; |                               |WIDTH and cell HEIGHT.            |
;; +-------------------------------+----------------------------------+
;; |`table-insert-row'             |Insert row(s) of cells before the |
;; |                               |current row that matches the      |
;; |                               |current row structure.            |
;; +-------------------------------+----------------------------------+
;; |`table-insert-column'          |Insert column(s) of cells before  |
;; |                               |the current column that matches   |
;; |                               |the current column structure.     |
;; +-------------------------------+----------------------------------+
;; |`table-delete-row'             |Delete row(s) of cells.  The row  |
;; |                               |must consist from cells of the    |
;; |                               |same height.                      |
;; +-------------------------------+----------------------------------+
;; |`table-delete-column'          |Delete column(s) of cells.  The   |
;; |                               |column must consist from cells of |
;; |                               |the same width.                   |
;; +-------------------------------+----------------------------------+
;; |`table-recognize'              |Recognize all tables in the       |
;; |`table-unrecognize'            |current buffer and                |
;; |                               |activate/inactivate them.         |
;; +-------------------------------+----------------------------------+
;; |`table-recognize-region'       |Recognize all the cells in a      |
;; |`table-unrecognize-region'     |region and activate/inactivate    |
;; |                               |them.                             |
;; +-------------------------------+----------------------------------+
;; |`table-recognize-table'        |Recognize all the cells in a      |
;; |`table-unrecognize-table'      |single table and                  |
;; |                               |activate/inactivate them.         |
;; +-------------------------------+----------------------------------+
;; |`table-recognize-cell'         |Recognize a cell.  Find a cell    |
;; |`table-unrecognize-cell'       |which contains the current point  |
;; |                               |and activate/inactivate that cell.|
;; +-------------------------------+----------------------------------+
;; |`table-forward-cell'           |Move point to the next Nth cell in|
;; |                               |a table.                          |
;; +-------------------------------+----------------------------------+
;; |`table-backward-cell'          |Move point to the previous Nth    |
;; |                               |cell in a table.                  |
;; +-------------------------------+----------------------------------+
;; |`table-span-cell'              |Span the current cell toward the  |
;; |                               |specified direction and merge it  |
;; |                               |with the adjacent cell.  The      |
;; |                               |direction is right, left, above or|
;; |                               |below.                            |
;; +-------------------------------+----------------------------------+
;; |`table-split-cell-vertically'  |Split the current cell vertically |
;; |                               |and create a cell above and a cell|
;; |                               |below the point location.         |
;; +-------------------------------+----------------------------------+
;; |`table-split-cell-horizontally'|Split the current cell            |
;; |                               |horizontally and create a cell on |
;; |                               |the left and a cell on the right  |
;; |                               |of the point location.            |
;; +-------------------------------+----------------------------------+
;; |`table-split-cell'             |Split the current cell vertically |
;; |                               |or horizontally.  This is a       |
;; |                               |wrapper command to the other two  |
;; |                               |orientation specific commands.    |
;; +-------------------------------+----------------------------------+
;; |`table-heighten-cell'          |Heighten the current cell.        |
;; +-------------------------------+----------------------------------+
;; |`table-shorten-cell'           |Shorten the current cell.         |
;; +-------------------------------+----------------------------------+
;; |`table-widen-cell'             |Widen the current cell.           |
;; +-------------------------------+----------------------------------+
;; |`table-narrow-cell'            |Narrow the current cell.          |
;; +-------------------------------+----------------------------------+
;; |`table-fixed-width-mode'       |Toggle fixed width mode.  In the  |
;; |                               |fixed width mode, typing inside a |
;; |                               |cell never changes the cell width,|
;; |                               |while in the normal mode the cell |
;; |                               |width expands automatically in    |
;; |                               |order to prevent a word being     |
;; |                               |folded into multiple lines.  Fixed|
;; |                               |width mode reverses video or      |
;; |                               |underline the cell contents for   |
;; |                               |its indication.                   |
;; +-------------------------------+----------------------------------+
;; |`table-query-dimension'        |Compute and report the current    |
;; |                               |cell dimension, current table     |
;; |                               |dimension and the number of       |
;; |                               |columns and rows in the table.    |
;; +-------------------------------+----------------------------------+
;; |`table-generate-source'        |Generate the source of the current|
;; |                               |table in the specified language   |
;; |                               |and insert it into a specified    |
;; |                               |buffer.                           |
;; +-------------------------------+----------------------------------+
;; |`table-insert-sequence'        |Travel cells forward while        |
;; |                               |inserting a specified sequence    |
;; |                               |string into each cell.            |
;; +-------------------------------+----------------------------------+
;; |`table-capture'                |Convert plain text into a table by|
;; |                               |capturing the text in the region. |
;; +-------------------------------+----------------------------------+
;; |`table-release'                |Convert a table into plain text by|
;; |                               |removing the frame from a table.  |
;; +-------------------------------+----------------------------------+
;; |`table-justify'                |Justify the contents of cell(s).  |
;; +-------------------------------+----------------------------------+
;;
;;
;; *Note*
;;
;; You may find that some of commonly expected table commands are
;; missing such as copying a row/column and yanking it.  Those
;; functions can be obtained through existing Emacs text editing
;; commands.  Rows are easily manipulated with region commands and
;; columns can be copied and pasted through rectangle commands.  After
;; all a table is still a part of text in the buffer.  Only the
;; special behaviors exist inside each cell through text properties.
;;
;; `table-generate-html' which appeared in earlier releases is
;; deprecated in favor of `table-generate-source'.  Now HTML is
;; treated as one of the languages used for describing the table's
;; logical structure.
;;
;;
;; -------
;; Keymap:
;; -------
;;
;; Although this package does not use a mode it does use its own
;; keymap inside a table cell by way of keymap text property.  Some of
;; the standard basic editing commands bound to certain keys are
;; replaced with the table specific version of corresponding commands.
;; This replacement combination is listed in the constant alist
;; `table-command-remap-alist' declared below.  This alist is
;; not meant to be user configurable but mentioned here for your
;; better understanding of using this package.  In addition, table
;; cells have some table specific bindings for cell navigation and
;; cell reformation.  You can find these additional bindings in the
;; constant `table-cell-bindings'.  Those key bound functions are
;; considered as internal functions instead of normal commands,
;; therefore they have special prefix, *table-- instead of table-, for
;; symbols.  The purpose of this is to make it easier for a user to
;; use command name completion.  There is a "normal hooks" variable
;; `table-cell-map-hook' prepared for users to override the default
;; table cell bindings.  Following is the table of predefined default
;; key bound commands inside a table cell.  Remember these bindings
;; exist only inside a table cell.  When your terminal is a tty, the
;; control modifier may not be available or applicable for those
;; special characters.  In this case use "C-cC-c", which is
;; customizable via `table-command-prefix', as the prefix key
;; sequence.  This should preceding the following special character
;; without the control modifier.  For example, use "C-cC-c|" instead
;; of "C-|".
;;
;; +------------------------------------------------------------------+
;; |                Default Bindings in a Table Cell                  |
;; +-------+----------------------------------------------------------+
;; |  Key  |                      Function                            |
;; +-------+----------------------------------------------------------+
;; |  TAB  |Move point forward to the beginning of the next cell.     |
;; +-------+----------------------------------------------------------+
;; | "C->" |Widen the current cell.                                   |
;; +-------+----------------------------------------------------------+
;; | "C-<" |Narrow the current cell.                                  |
;; +-------+----------------------------------------------------------+
;; | "C-}" |Heighten the current cell.                                |
;; +-------+----------------------------------------------------------+
;; | "C-{" |Shorten the current cell.                                 |
;; +-------+----------------------------------------------------------+
;; | "C--" |Split current cell vertically. (one above and one below)  |
;; +-------+----------------------------------------------------------+
;; | "C-|" |Split current cell horizontally. (one left and one right) |
;; +-------+----------------------------------------------------------+
;; | "C-*" |Span current cell into adjacent one.                      |
;; +-------+----------------------------------------------------------+
;; | "C-+" |Insert row(s)/column(s).                                  |
;; +-------+----------------------------------------------------------+
;; | "C-!" |Toggle between normal mode and fixed width mode.          |
;; +-------+----------------------------------------------------------+
;; | "C-#" |Report cell and table dimension.                          |
;; +-------+----------------------------------------------------------+
;; | "C-^" |Generate the source in a language from the current table. |
;; +-------+----------------------------------------------------------+
;; | "C-:" |Justify the contents of cell(s).                          |
;; +-------+----------------------------------------------------------+
;;
;; *Note*
;;
;; When using `table-cell-map-hook' do not use `local-set-key'.
;;
;;   (add-hook 'table-cell-map-hook
;;     (function (lambda ()
;;       (local-set-key [<key sequence>] '<function>))))
;;
;; Above code is well known ~/.emacs idiom for customizing a mode
;; specific keymap however it does not work for this package.  This is
;; because there is no table mode in effect.  This package does not
;; use a local map therefor you must modify `table-cell-map'
;; explicitly.  The correct way of achieving above task is:
;;
;;   (add-hook 'table-cell-map-hook
;;     (function (lambda ()
;;       (define-key table-cell-map [<key sequence>] '<function>))))
;;
;; -----
;; Menu:
;; -----
;;
;; If a menu system is available a group of table specific menu items,
;; "Table" under "Tools" section of the menu bar, is globally added
;; after this package is loaded.  The commands in this group are
;; limited to the ones that are related to creation and initialization
;; of tables, such as to insert a table, to insert rows and columns,
;; or recognize and unrecognize tables.  Once tables are created and
;; point is placed inside of a table cell a table specific menu item
;; "Table" appears directly on the menu bar.  The commands in this
;; menu give full control on table manipulation that include cell
;; navigation, insertion, splitting, spanning, shrinking, expansion
;; and unrecognizing.  In addition to above two types of menu there is
;; a pop-up menu available within a table cell.  The content of pop-up
;; menu is identical to the full table menu.  [mouse-3] is the default
;; button, defined in `table-cell-bindings', to bring up the pop-up
;; menu.  It can be reconfigured via `table-cell-map-hook'.  The
;; benefit of a pop-up menu is that it combines selection of the
;; location (which cell, where in the cell) and selection of the
;; desired operation into a single clicking action.
;;
;;
;; -------------------------------
;; Definition of tables and cells:
;; -------------------------------
;;
;; There is no artificial-intelligence magic in this package.  The
;; definition of a table and the cells inside the table is reasonably
;; limited in order to achieve acceptable performance in the
;; interactive operation under Emacs lisp implementation.  A valid
;; table is a rectangular text area completely filled with valid
;; cells.  A valid cell is a rectangle text area, which four borders
;; consist of valid border characters.  Cells can not be nested one to
;; another or overlapped to each other except sharing the border
;; lines.  A valid character of a cell's vertical border is either
;; table-cell-vertical-char `|' or table-cell-intersection-char `+'.
;; A valid character of a cell's horizontal border is either
;; table-cell-horizontal-char `-' or table-cell-intersection-char `+'.
;; A valid character of the four corners of a cell must be
;; table-cell-intersection-char `+'.  A cell must contain at least one
;; character space inside.  There is no restriction about the contents
;; of a table cell, however it is advised if possible to avoid using
;; any of the border characters inside a table cell.  Normally a few
;; boarder characters inside a table cell are harmless.  But it is
;; possible that they accidentally align up to emulate a bogus cell
;; corner on which software relies on for cell recognition.  When this
;; happens the software may be fooled by it and fail to determine
;; correct cell dimension.
;;
;; Following are the examples of valid tables.
;;
;; +--+----+---+     +-+     +--+-----+
;; |  |    |   |     | |     |  |     |
;; +--+----+---+     +-+     |  +--+--+
;; |  |    |   |             |  |  |  |
;; +--+----+---+             +--+--+  |
;;                           |     |  |
;;                           +-----+--+
;;
;; The next five tables are the examples of invalid tables.  (From
;; left to right, 1. nested cells 2. overlapped cells and a
;; non-rectangle cell 3. non-rectangle table 4. zero width/height
;; cells 5. zero sized cell)
;;
;; +-----+    +-----+       +--+    +-++--+    ++
;; |     |    |     |       |  |    | ||  |    ++
;; | +-+ |    |     |       |  |    | ||  |
;; | | | |    +--+  |    +--+--+    +-++--+
;; | +-+ |    |  |  |    |  |  |    +-++--+
;; |     |    |  |  |    |  |  |    | ||  |
;; +-----+    +--+--+    +--+--+    +-++--+
;;
;; Although the program may recognizes some of these invalid tables,
;; results from the subsequent editing operations inside those cells
;; are not predictable and will most likely start destroying the table
;; structures.
;;
;; It is strongly recommended to have at least one blank line above
;; and below a table.  For a table to coexist peacefully with
;; surrounding environment table needs to be separated from unrelated
;; text.  This is necessary for the left table to grow or shrink
;; horizontally without breaking the right table in the following
;; example.
;;
;;                          +-----+-----+-----+
;;  +-----+-----+           |     |     |     |
;;  |     |     |           +-----+-----+-----+
;;  +-----+-----+           |     |     |     |
;;                          +-----+-----+-----+
;;
;;
;; -------------------------
;; Cell contents formatting:
;; -------------------------
;;
;; The cell contents are formatted by filling a paragraph immediately
;; after characters are inserted into or deleted from a cell.  Because
;; of this, cell contents always remain fit inside a cell neatly.  One
;; drawback of this is that users do not have full control over
;; spacing between words and line breaking.  Only one space can be
;; entered between words and up to two spaces between sentences.  For
;; a newline to be effective the new line must form a beginning of
;; paragraph, otherwise it'll automatically be merged with the
;; previous line in a same paragraph.  To form a new paragraph the
;; line must start with some space characters or immediately follow a
;; blank line.  Here is a typical example of how to list items within
;; a cell.  Without a space at the beginning of each line the items
;; can not stand on their own.
;;
;; +---------------------------------+
;; |Each one of the following three  |
;; |items starts with a space        |
;; |character thus forms a paragraph |
;; |of its own.  Limitations in cell |
;; |contents formatting are:         |
;; |                                 |
;; | 1. Only one space between words.|
;; | 2. Up to two spaces between     |
;; |sentences.                       |
;; | 3. A paragraph must start with  |
;; |spaces or follow a blank line.   |
;; |                                 |
;; |This paragraph stays away from   |
;; |the item 3 because there is a    |
;; |blank line between them.         |
;; +---------------------------------+
;;
;; In the normal operation table cell width grows automatically when
;; certain word has to be folded into the next line if the width had
;; not been increased.  This normal operation is useful and
;; appropriate for most of the time, however, it is sometimes useful
;; or necessary to fix the width of table and width of table cells.
;; For this purpose the package provides fixed width mode.  You can
;; toggle between fixed width mode and normal mode by "C-!".
;;
;; Here is a simple example of the fixed width mode.  Suppose we have
;; a table like this one.
;;
;; +-----+
;; |     |
;; +-----+
;;
;; In normal mode if you type a word "antidisestablishmentarianism" it
;; grows the cell horizontally like this.
;;
;; +----------------------------+
;; |antidisestablishmentarianism|
;; +----------------------------+
;;
;;  In the fixed width mode the same action produces the following
;;  result.  The folded locations are indicated by a continuation
;;  character (`\' is the default).  The continuation character is
;;  treated specially so it is recommended to choose a character that
;;  does not appear elsewhere in table cells.  This character is
;;  configurable via customization and is kept in the variable
;;  `table-word-continuation-char'.  The continuation character is
;;  treated specially only in the fixed width mode and has no special
;;  meaning in the normal mode however.
;;
;; +-----+
;; |anti\|
;; |dise\|
;; |stab\|
;; |lish\|
;; |ment\|
;; |aria\|
;; |nism |
;; +-----+
;;
;;
;; -------------------
;; Cell Justification:
;; -------------------
;;
;; By default the cell contents are filled with left justification and
;; no vertical justification.  A paragraph can be justified
;; individually but only horizontally.  Paragraph justification is for
;; appearance only and does not change any structural information
;; while cell justification affects table's structural information.
;; For cell justification a user can select horizontal justification
;; and vertical justification independently.  Horizontal justification
;; must be one of the three 'left, 'center or 'right.  Vertical
;; justification can be 'top, 'middle, 'bottom or 'none.  When a cell
;; is justified, that information is recorded as a part of text
;; property therefore the information is persistent as long as the
;; cell remains within the Emacs world.  Even copying tables by region
;; and rectangle manipulation commands preserve this information.
;; However, once the table text is saved as a file and the buffer is
;; killed the justification information vanishes permanently.  To
;; alleviate this shortcoming without forcing users to save and
;; maintain a separate attribute file, the table code detects
;; justification of each cell when recognizing a table.  This
;; detection is done by guessing the justification by looking at the
;; appearance of the cell contents.  Since it is a guessing work it
;; does not guarantee the perfectness but it is designed to be
;; practically good enough.  The guessing algorithm is implemented in
;; the function `table--detect-cell-alignment'.  If you have better
;; algorithm or idea any suggestion is welcome.
;;
;;
;; -----
;; Todo: (in the order of priority, some are just possibility)
;; -----
;;
;; Fix compatibilities with other input method than quail
;; Resolve conflict with flyspell
;; Use mouse for resizing cells
;; A mechanism to link cells internally
;; Consider the use of variable width font under Emacs 21
;; Consider the use of `:box' face attribute under Emacs 21
;; Consider the use of `modification-hooks' text property instead of
;; rebinding the keymap
;; Maybe provide complete XEmacs support in the future however the
;; "extent" is the single largest obstacle lying ahead, read the
;; document in Emacs info.
;; (eval '(progn (require 'info) (Info-find-node "elisp" "Not Intervals")))
;;
;;
;; ---------------
;; Acknowledgment:
;; ---------------
;;
;; Table would not have been possible without the help and
;; encouragement of the following spirited contributors.
;;
;; Paul Georgief <georgief@igpp.ucsd.edu> has been the best tester
;; of the code as well as the constructive criticizer.
;;
;; Gerd Moellmann <gerd@gnu.org> gave me useful suggestions from Emacs
;; 21 point of view.