[elpa] 266/299: Auto insertion of ampersands.

[Stefan Monnier]

monnier pushed a commit to branch externals/auctex
in repository elpa.

commit 6c32c786d6161c8e83f134d4a2250f5234edae31
Author: Ikumi Keita <address@hidden>
Date:   Thu Jul 17 21:59:33 2014 +0200

    Auto insertion of ampersands.
    
    * latex.el: Enhance array and tabular(*) environments support.
    (LaTeX-env-array): Add call to `LaTeX-item-array'.
    (LaTeX-env-tabular*): Add call to `LaTeX-item-tabular*'.
    (LaTeX-array-skipping-regexp): New variable.
    (LaTeX-tabular*-skipping-regexp): Ditto.
    (LaTeX-item-array): New function.  Put line break macro on the
    last line and insert suitable number of ampersands.
    (LaTeX-item-tabular*): Ditto.
    (LaTeX-insert-ampersands): New function.  Insert suitable number
    of ampersands.
    (LaTeX-array-column-letters): New variable.  Column letters for
    array-like environments.
    (LaTeX-array-count-columns): New function.  Count number of
    ampersands to be inserted.
    (LaTeX-common-initialization): Add entries to LaTeX-item-list to
    use `LaTeX-item-array' and `LaTeX-item-tabular*'.
    
    * style/amsmath.el: Enhance alignat-like environments support
    as well as some cleanups.
    (LaTeX-item-equation-alignat): New function.  Insert contents to
    terminate a line in multi-line equations environment.
    (LaTeX-amsmath-env-alignat): Use it.  Add doc string.
    (LaTeX-amsmath-env-alignedat): Ditto.
    (LaTeX-amsmath-env-aligned): Removed.  Just specifying a prompt
    string for an optional argument is enough.
    (LaTeX-item-equation): Take over the job of
    `LaTeX-item-equations'.  Add an optional `suppress' argument:
    when it is non-nil skip putting line break macro.  Add doc string.
    (LaTeX-item-equations): Removed.  Its task is now covered by
    `LaTeX-item-equation'.
    (LaTeX-item-equation-alignat): New function.  Insert ampersands
    according to the columns number, as well as calling
    `LaTeX-item-equation'.
    (LaTeX-amsmath-alignat-number-of-ampersands): New function.
    ("amsmath"): Arrange setups of variables to adopt the above
    changes.
    
    * style/array.el ("array"): Change `LaTeX-array-column-letters'
    locally to include addtional letters extended in array.sty.
    
    * style/plext.el: New style file.  Add support for extended
    format for array-like environments.
    
    * Makefile.in (STYLESRC): Include style/plext.el.
    
    * doc/auctex.texi: Add documentation for the above enhancements.
    
    * doc/changes.texi: Ditto.
    
    Signed-off-by: Mosè Giordano <address@hidden>
---
 ChangeLog        |   51 +++++++++++++++++++++
 Makefile.in      |    2 +-
 doc/auctex.texi  |   21 +++++++++
 doc/changes.texi |   13 +++++
 latex.el         |  131 ++++++++++++++++++++++++++++++++++++++++++++++++++++-
 style/amsmath.el |  104 +++++++++++++++++++++++++-----------------
 style/array.el   |    5 ++-
 style/plext.el   |   77 +++++++++++++++++++++++++++++++
 8 files changed, 357 insertions(+), 47 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 4162bec..9ed3607 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,54 @@
+2014-07-15  Ikumi Keita  <address@hidden>
+
+       * latex.el: Enhance array and tabular(*) environments support.
+       (LaTeX-env-array): Add call to `LaTeX-item-array'.
+       (LaTeX-env-tabular*): Add call to `LaTeX-item-tabular*'.
+       (LaTeX-array-skipping-regexp): New variable.
+       (LaTeX-tabular*-skipping-regexp): Ditto.
+       (LaTeX-item-array): New function.  Put line break macro on the
+       last line and insert suitable number of ampersands.
+       (LaTeX-item-tabular*): Ditto.
+       (LaTeX-insert-ampersands): New function.  Insert suitable number
+       of ampersands.
+       (LaTeX-array-column-letters): New variable.  Column letters for
+       array-like environments.
+       (LaTeX-array-count-columns): New function.  Count number of
+       ampersands to be inserted.
+       (LaTeX-common-initialization): Add entries to LaTeX-item-list to
+       use `LaTeX-item-array' and `LaTeX-item-tabular*'.
+
+       * style/amsmath.el: Enhance alignat-like environments support
+       as well as some cleanups.
+       (LaTeX-item-equation-alignat): New function.  Insert contents to
+       terminate a line in multi-line equations environment.
+       (LaTeX-amsmath-env-alignat): Use it.  Add doc string.
+       (LaTeX-amsmath-env-alignedat): Ditto.
+       (LaTeX-amsmath-env-aligned): Removed.  Just specifying a prompt
+       string for an optional argument is enough.
+       (LaTeX-item-equation): Take over the job of
+       `LaTeX-item-equations'.  Add an optional `suppress' argument:
+       when it is non-nil skip putting line break macro.  Add doc string.
+       (LaTeX-item-equations): Removed.  Its task is now covered by
+       `LaTeX-item-equation'.
+       (LaTeX-item-equation-alignat): New function.  Insert ampersands
+       according to the columns number, as well as calling
+       `LaTeX-item-equation'.
+       (LaTeX-amsmath-alignat-number-of-ampersands): New function.
+       ("amsmath"): Arrange setups of variables to adopt the above
+       changes.
+
+       * style/array.el ("array"): Change `LaTeX-array-column-letters'
+       locally to include addtional letters extended in array.sty.
+
+       * style/plext.el: New style file.  Add support for extended
+       format for array-like environments.
+
+       * Makefile.in (STYLESRC): Include style/plext.el.
+
+       * doc/auctex.texi: Add documentation for the above enhancements.
+
+       * doc/changes.texi: Ditto.
+
 2014-07-14  Mos� Giordano  <address@hidden>
 
        * tex-buf.el (TeX-next-error): Do not pass `reparse' argument to
diff --git a/Makefile.in b/Makefile.in
index b69cf0c..21895fb 100644
--- a/Makefile.in
+++ b/Makefile.in
@@ -134,7 +134,7 @@ STYLESRC = style/prosper.el \
           style/acronym.el   style/xparse.el    style/fancyvrb.el \
           style/tabulary.el  style/fontspec.el  style/unicode-math.el \
           style/luacode.el   style/metalogo.el  style/english.el \
-          style/exercise.el
+          style/exercise.el  style/plext.el
 STYLEELC = $(STYLESRC:.el=.elc)
 
 CLEANFILES = $(AUCELC) $(STYLEELC) $(MULEELC)
diff --git a/doc/auctex.texi b/doc/auctex.texi
index 48ffd0e..3961bb8 100644
--- a/doc/auctex.texi
+++ b/doc/auctex.texi
@@ -1033,6 +1033,7 @@ Otherwise, you will be asked only in description 
environments.
 
 @node Tabular-like
 @subsection Tabular-like Environments
address@hidden amsmath
 
 When inserting Tabular-like environments, that is, `tabular' `array'
 etc., you will be prompted for a template for that environment.
@@ -1051,6 +1052,26 @@ Default position string for array and tabular 
environments.  If nil,
 act like the empty string is given, but don't prompt for a position.
 @end defopt
 
address@hidden calculates the number of columns from the format string and
+inserts the suitable number of ampersands.
+
+You can use @kbd{C-c @key{LFD}} (@code{LaTeX-insert-item}) to terminate
+rows in these environments.  It supplies line break macro @samp{\\} and
+inserts the suitable number of ampersands on the next line.
+
address@hidden Command LaTeX-insert-item
address@hidden C-c @key{LFD}
+(@kbd{C-c @key{LFD}}) Close the current row with @samp{\\}, move to the
+next line and insert an appropriate number of ampersands for the current
+environment.
address@hidden deffn
+
+Similar supports are provided for various amsmath environments such as
address@hidden, @samp{gather}, @samp{alignat}, @samp{matrix} etc.  Try
+typing @kbd{C-c @key{LFD}} in these environments.  It recognizes the
+current environment and does the appropriate job depending on the
+context.
+
 @node Customizing Environments
 @subsection Customizing Environments
 
diff --git a/doc/changes.texi b/doc/changes.texi
index 903d42e..5707cd0 100644
--- a/doc/changes.texi
+++ b/doc/changes.texi
@@ -101,6 +101,19 @@ column values of a table line are written across multiple 
lines in the
 tex file.
 
 @item
+The suitable number of ampersands are inserted when you insert array,
+tabular and tabular* environments with @kbd{C-c C-e}.  Similar
+experience is obtained if you terminate rows in these environments with
address@hidden @key{LFD}}.  It supplies line break macro @samp{\\} and inserts
+the suitable number of ampersands on the next line.
+
+Similar supports are provided for various amsmath environments.
+
address@hidden rawfile
address@hidden, for details.
address@hidden ifclear
+
address@hidden
 Commands for narrowing to a group (@code{TeX-narrow-to-group}) and to
 @LaTeX{} environments (@code{LaTeX-narrow-to-environment}) were added.
 
diff --git a/latex.el b/latex.el
index 5ba3efb..d9a383f 100644
--- a/latex.el
+++ b/latex.el
@@ -1028,7 +1028,8 @@ Just like array and tabular."
                              (concat
                               (unless (zerop (length pos))
                                 (concat LaTeX-optop pos LaTeX-optcl))
-                              (concat TeX-grop fmt TeX-grcl)))))
+                              (concat TeX-grop fmt TeX-grcl)))
+    (LaTeX-item-array t)))
 
 (defun LaTeX-env-label (environment)
   "Insert ENVIRONMENT and prompt for label."
@@ -1076,7 +1077,8 @@ Just like array and tabular."
                               (concat TeX-grop width TeX-grcl) ;; not optional!
                               (unless (zerop (length pos))
                                 (concat LaTeX-optop pos LaTeX-optcl))
-                              (concat TeX-grop fmt TeX-grcl)))))
+                              (concat TeX-grop fmt TeX-grcl)))
+    (LaTeX-item-tabular* t)))
 
 (defun LaTeX-env-picture (environment)
   "Insert ENVIRONMENT with width, height specifications."
@@ -1154,6 +1156,126 @@ You may use `LaTeX-item-list' to change the routines 
used to insert the item."
   "Insert a new bibitem."
   (TeX-insert-macro "bibitem"))
 
+(defvar LaTeX-array-skipping-regexp (regexp-opt '("[t]" "[b]" ""))
+   "Regexp matching between \\begin{xxx} and column specification.
+For array and tabular environments.  See `LaTeX-insert-ampersands' for
+detail.")
+
+(defvar LaTeX-tabular*-skipping-regexp
+  ;; Assume width specification contains neither nested curly brace
+  ;; pair nor escaped "}".
+  (concat "{[^}]*}[ \t]*" (regexp-opt '("[t]" "[b]" "")))
+   "Regexp matching between \\begin{tabular*} and column specification.
+For tabular* environment only.  See `LaTeX-insert-ampersands' for detail.")
+
+(defun LaTeX-item-array (&optional suppress)
+  "Insert line break macro on the last line and suitable number of &'s.
+For array and tabular environments.
+
+If SUPPRESS is non-nil, do not insert line break macro."
+  (unless suppress
+    (save-excursion
+      (end-of-line 0)
+      (just-one-space)
+      (TeX-insert-macro "\\")))
+  (LaTeX-insert-ampersands
+   LaTeX-array-skipping-regexp 'LaTeX-array-count-columns))
+
+(defun LaTeX-item-tabular* (&optional suppress)
+  "Insert line break macro on the last line and suitable number of &'s.
+For tabular* environment only.
+
+If SUPPRESS is non-nil, do not insert line break macro."
+  (unless suppress
+    (save-excursion
+      (end-of-line 0)
+      (just-one-space)
+      (TeX-insert-macro "\\")))
+  (LaTeX-insert-ampersands
+   LaTeX-tabular*-skipping-regexp 'LaTeX-array-count-columns))
+
+(defun LaTeX-insert-ampersands (regexp func)
+  "Insert suitable number of ampersands for the current environment.
+The number is calculated from REGEXP and FUNC.
+
+Example 1:
+Consider the case that the current environment begins with
+\\begin{array}[t]{|lcr|}
+.  REGEXP must be chosen to match \"[t]\", i.e., the text between just
+after \"\\begin{array}\" and just before \"{|lcr|}\", which encloses
+the column specification.  FUNC must return the number of ampersands to
+be inserted, which is 2 since this example specifies three columns.
+FUNC is called with two arguments START and END, which spans the column
+specification (without enclosing braces.)  REGEXP is used to determine
+these START and END.
+
+Example 2:
+This time the environment begins with
address@hidden,}p{5ex}}
+.  REGEXP must match \"{1.0\\linewidth}[b]\" and FUNC must return 1 from
+the text \"address@hidden,}p{5ex}\" between START and END specified two 
columns.
+
+FUNC should return nil if it cannot determine the number of ampersands."
+  (let* ((cur (point))
+        (num
+         (save-excursion
+           (ignore-errors
+             (LaTeX-find-matching-begin)
+             ;; Skip over "\begin{xxx}" and possible whitespaces.
+             (forward-list 1)
+             (skip-chars-forward " \t")
+             ;; Skip over the text specified by REGEXP and whitespaces.
+             (when (let ((case-fold-search nil))
+                     (re-search-forward regexp cur))
+               (skip-chars-forward " \t")
+               (when (eq (following-char) ?{)
+                 ;; We have reached the target "{yyy}" part.
+                 (forward-char 1)
+                 ;; The next line doesn't move point, so point
+                 ;; is left just after the opening brace.
+                 (let ((pos (TeX-find-closing-brace)))
+                   (if pos
+                       ;; Calculate number of ampersands to be inserted.
+                       (funcall func (point) (1- pos))))))))))
+    (if (natnump num)
+       (save-excursion (insert (make-string num ?&))))))
+
+(defvar LaTeX-array-column-letters "clrp"
+  "Column letters for array-like environments.
+See `LaTeX-array-count-columns' for detail.")
+
+(defun LaTeX-array-count-columns (start end)
+  "Count number of ampersands to be inserted.
+The columns are specified by the letters found in the string
+`LaTeX-array-column-letters' and the number of those letters within the
+text between START and END is basically considered to be the number of
+columns.  The arguments surrounded between braces such as p{30pt} do not
+interfere the count of columns.
+
+Return one less number than the columns, or nil on failing to count the
+right number."
+  (save-excursion
+    (let (p (cols 0))
+      (goto-char start)
+      (while (< (setq p (point)) end)
+
+       ;; The below block accounts for one unit of move for
+       ;; one column.
+       (setq cols (+ cols (skip-chars-forward
+                           LaTeX-array-column-letters end)))
+       (skip-chars-forward (concat
+                            "^" LaTeX-array-column-letters
+                            TeX-grop) end)
+       (if (eq (following-char) ?{) (forward-list 1))
+
+       ;; Not sure whether this is really necessary or not, but
+       ;; prepare for possible infinite loop anyway.
+       (when (eq p (point))
+         (setq cols nil)
+         (goto-char end)))
+      ;; The number of ampersands is one less than column.
+      (if cols (1- cols)))))
+
 ;;; Parser
 
 (defvar LaTeX-auto-style nil)
@@ -5678,7 +5800,10 @@ i.e. you do _not_ have to cater for this yourself by 
adding \\\\' or $."
 
   (make-local-variable 'LaTeX-item-list)
   (setq LaTeX-item-list '(("description" . LaTeX-item-argument)
-                         ("thebibliography" . LaTeX-item-bib)))
+                         ("thebibliography" . LaTeX-item-bib)
+                         ("array" . LaTeX-item-array)
+                         ("tabular" . LaTeX-item-array)
+                         ("tabular*" . LaTeX-item-tabular*)))
 
   (setq TeX-complete-list
        (append '(("\\\\cite\\[[^]\n\r\\%]*\\]{\\([^{}\n\r\\%,]*\\)"
diff --git a/style/amsmath.el b/style/amsmath.el
index 19e6dfe..8faf308 100644
--- a/style/amsmath.el
+++ b/style/amsmath.el
@@ -43,8 +43,8 @@
      '("xalignat"   LaTeX-amsmath-env-alignat)
      '("xalignat*"  LaTeX-amsmath-env-alignat)
      '("xxalignat"  LaTeX-amsmath-env-alignat)
-     '("aligned"    LaTeX-amsmath-env-aligned)
-     '("gathered"   LaTeX-amsmath-env-aligned)
+     '("aligned"    ["Vertical position (t or b)"])
+     '("gathered"   ["Vertical position (t or b)"])
      '("alignedat"  LaTeX-amsmath-env-alignedat)
      "align*" "gather*" "flalign*" "multline*" "equation*"
      "split"
@@ -104,19 +104,19 @@
           (append '(("split"    . LaTeX-item-equation)
                     ("multline" . LaTeX-item-equation)
                     ("multline*" . LaTeX-item-equation)
-                    ("gather"   . LaTeX-item-equations)
+                    ("gather"   . LaTeX-item-equation)
                     ("gather*"  . LaTeX-item-equation)
                     ("gathered" . LaTeX-item-equation)
-                    ("align"    . LaTeX-item-equations)
+                    ("align"    . LaTeX-item-equation)
                     ("align*"   . LaTeX-item-equation)
                     ("aligned"  . LaTeX-item-equation)
-                    ("alignat"  . LaTeX-item-equations)
-                    ("alignat*" . LaTeX-item-equation)
-                    ("xalignat"  . LaTeX-item-equations)
-                    ("xalignat*" . LaTeX-item-equation)
-                    ("xxalignat" . LaTeX-item-equation)
-                    ("alignedat" . LaTeX-item-equation)
-                    ("flalign"  . LaTeX-item-equations)
+                    ("alignat"  . LaTeX-item-equation-alignat)
+                    ("alignat*" . LaTeX-item-equation-alignat)
+                    ("xalignat"  . LaTeX-item-equation-alignat)
+                    ("xalignat*" . LaTeX-item-equation-alignat)
+                    ("xxalignat" . LaTeX-item-equation-alignat)
+                    ("alignedat" . LaTeX-item-equation-alignat)
+                    ("flalign"  . LaTeX-item-equation)
                     ("flalign*" . LaTeX-item-equation)
                     ("matrix" .  LaTeX-item-equation)
                     ("pmatrix" .  LaTeX-item-equation)
@@ -136,7 +136,7 @@
          (append '(("align"      . LaTeX-amsmath-label)
                    ("alignat"    . LaTeX-amsmath-label)
                    ("xalignat"   . LaTeX-amsmath-label)
-                   ("multline"    . LaTeX-amsmath-label)
+                   ("multline"   . LaTeX-amsmath-label)
                    ("flalign"    . LaTeX-amsmath-label)
                    ("gather"     . LaTeX-amsmath-label))
                  LaTeX-label-alist))
@@ -158,40 +158,60 @@
       (reftex-add-to-label-alist '(AMSTeX))))))
 
 (defun LaTeX-amsmath-env-alignat (env)
+  "Insert ENV with column number specifications.
+Insert suitable number of ampersands also if possible."
   (let ((ncols (read-string "Number of columns: ")))
     (LaTeX-insert-environment env (concat TeX-grop ncols TeX-grcl))
-    (and (not (string= "xxalignat" env))
-        (not (string= "*" (substring env -1)))
-        (LaTeX-label env)
-        (newline-and-indent))))
-
-(defun LaTeX-amsmath-env-aligned (env)
-  (let ((where (read-string "(optional) Vertical position (t or b): ")))
-    (if (string= where "")
-       (setq where "")
-      (setq where (concat "[" where "]")))
-    (LaTeX-insert-environment env where)))
+    (LaTeX-item-equation-alignat t)))
 
 (defun LaTeX-amsmath-env-alignedat (env)
-  (let ((where (read-string "(optional) Vertical position (t or b): "))
-     (ncols (read-string "Number of columns: ")))
-    (if (string= where "")
-     (setq where "")
-      (setq where (concat "[" where "]")))
-    (LaTeX-insert-environment env (concat where TeX-grop ncols TeX-grcl))))
-
-(defun LaTeX-item-equation ()
-  (end-of-line 0)
-  (just-one-space)
-  (insert "\\\\")
-  (forward-line 1)
-  (indent-according-to-mode))
-
-(defun LaTeX-item-equations ()
-  (LaTeX-item-equation)
-  (let ((environment (LaTeX-current-environment 1)))
-    (and (LaTeX-label environment)
-        (newline-and-indent))))
+  "Insert ENV with position and column number specifications.
+Insert suitable number of ampersands also if possible."
+  (let ((where (read-string "(Optional) Vertical position (t or b): "))
+       (ncols (read-string "Number of columns: ")))
+    (unless (string= where "")
+      (setq where (concat LaTeX-optop where LaTeX-optcl)))
+    (LaTeX-insert-environment env (concat where TeX-grop ncols TeX-grcl))
+    (LaTeX-item-equation-alignat t)))
+
+(defun LaTeX-item-equation (&optional suppress)
+  "Insert contents to terminate a line in multi-line equations environment.
+Put line break macro on the last line.  If the current environment
+wants \\label, insert it also.
+
+If SUPPRESS is non-nil, do not insert line break macro."
+  (unless suppress
+    (end-of-line 0)
+    (just-one-space)
+    (TeX-insert-macro "\\")
+    (forward-line 1)
+    (indent-according-to-mode))
+  (let ((env (LaTeX-current-environment)))
+    (when (and (assoc env LaTeX-label-alist)
+              (LaTeX-label env))
+      (LaTeX-newline)
+      (indent-according-to-mode))))
+
+(defun LaTeX-item-equation-alignat (&optional suppress)
+  "Insert contents to terminate a line in multi-line equations environment.
+Put line break macro on the last line.  Next, if the current
+environment wants \\label, insert it also.  And insert suitable number
+of ampersands if possible.
+
+If SUPPRESS is non-nil, do not insert line break macro."
+  (LaTeX-item-equation suppress)
+  (LaTeX-insert-ampersands
+   (concat "\\(?:"
+          (regexp-quote LaTeX-optop) "[tb]" (regexp-quote LaTeX-optcl)
+          "\\)?")
+   'LaTeX-amsmath-alignat-number-of-ampersands))
+
+(defun LaTeX-amsmath-alignat-number-of-ampersands (start end)
+  "Return the number of ampersands to insert.
+The number is 2N-1 where N is the number taken from the text between
+START and END."
+  (let ((num (string-to-number (buffer-substring-no-properties start end))))
+    (if (integerp num) (+ num num -1))))
 
 (defvar LaTeX-amsmath-package-options '("intlimits" "nointlimits"
                                        "sumlimits" "nosumlimits"
diff --git a/style/array.el b/style/array.el
index 89c2222..7775abb 100644
--- a/style/array.el
+++ b/style/array.el
@@ -40,7 +40,10 @@
 
    ;; `array.sty' adds a couple of new lengths.  They're added here, rather 
than
    ;; in the `TeX-add-symbols' block.
-   (LaTeX-add-lengths "extratabsurround" "extrarowheight")))
+   (LaTeX-add-lengths "extratabsurround" "extrarowheight")
+
+   ;; `array.sty' adds some new column specification letters.
+   (set (make-local-variable 'LaTeX-array-column-letters) "clrpmb")))
 
 (defvar LaTeX-array-package-options nil
   "Package options for array.")
diff --git a/style/plext.el b/style/plext.el
new file mode 100644
index 0000000..062bced
--- /dev/null
+++ b/style/plext.el
@@ -0,0 +1,77 @@
+;;; plext.el --- AUCTeX style for the plext package.
+
+;; Copyright (C) 2014 Free Software Foundation, Inc.
+
+;; Author: Ikumi Keita <address@hidden>
+;; Maintainer: address@hidden
+;; Created: 2014-07-05
+;; Keywords: tex, japanese
+
+;; This file is part of AUCTeX.
+
+;; AUCTeX 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.
+
+;; AUCTeX 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 AUCTeX; see the file COPYING.  If not, write to the Free
+;; Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
+;; 02110-1301, USA.
+
+;;; Commentary:
+
+;; This file adds support for the plext package.
+
+;;; Code:
+
+(TeX-add-style-hook
+ "plext"
+ (lambda ()
+   ;; plext.sty extends some environments to accept option, e.g. <t>,
+   ;; for vertical typesetting.
+   (LaTeX-add-environments
+    ;; TODO: Add support for minipage and picture
+    ;; environments extension.
+    '("array"    LaTeX-plext-env-array)
+    '("tabular"  LaTeX-plext-env-array)
+    '("tabular*" LaTeX-plext-env-array))
+
+   (set (make-local-variable 'LaTeX-array-skipping-regexp)
+       (concat "\\(?:<[tyz]>\\)?[ \t]*" (regexp-opt '("[t]" "[b]" ""))))
+   (set (make-local-variable 'LaTeX-tabular*-skipping-regexp)
+       (concat "\\(?:<[tyz]>\\)?[ \t]*{[^}]*}[ \t]*"
+               (regexp-opt '("[t]" "[b]" ""))))))
+
+(defun LaTeX-plext-env-array (env)
+  (let ((dir (read-string "(Optional) Direction (t or y or z): "))
+       (width (if (string= env "tabular*")
+                  (read-string "Width: " LaTeX-default-width)))
+       (pos (and LaTeX-default-position ; LaTeX-default-position can
+                                       ; be nil, i.e. do not prompt
+                 (read-string "(Optional) Position: " LaTeX-default-position)))
+       (fmt (read-string "Format: " LaTeX-default-format)))
+    (unless (zerop (length dir))
+      (setq dir (concat "<" dir ">")))
+    (if (string= env "tabular*")
+       (setq LaTeX-default-width width))
+    (setq LaTeX-default-position pos)
+    (setq LaTeX-default-format fmt)
+    (LaTeX-insert-environment env
+                             (concat
+                              dir
+                              (if (string= env "tabular*")
+                                  (concat TeX-grop width TeX-grcl))
+                              (unless (zerop (length pos))
+                                (concat LaTeX-optop pos LaTeX-optcl))
+                              (concat TeX-grop fmt TeX-grcl)))
+    (if (string= env "tabular*")
+       (LaTeX-item-tabular* t)
+      (LaTeX-item-array t))))
+
+;;; plext.el ends here.