(indian-compose-regexp): New function.

(malayalam-composable-pattern): Fix the pattern.
(composition-function-table): Set malayalam-composable-pattern for
Malayalam characters.

lisp/language/indian.el

@@ -129,6 +129,15 @@ environment."))
 South Indian language Malayalam is supported in this language environment."))
  '("Indian"))
 
+;; Replace mnemonic characters in REGEXP according to TABLE.  TABLE is
+;; an alist of (MNEMONIC-STRING . REPLACEMENT-STRING).
+
+(defun indian-compose-regexp (regexp table)
+  (let ((case-fold-search nil))
+    (dolist (elt table)
+      (setq regexp (replace-regexp-in-string (car elt) (cdr elt) regexp t t)))
+    regexp))
+
 (defconst devanagari-composable-pattern
   (concat
    "\\([अ-औॠॡ][ँं]?\\)\\|[ः।]"
@@ -156,12 +165,27 @@ South Indian language Malayalam is supported in this language environment."))
   "Regexp matching a composable sequence of Kannada characters.")
 
 (defconst malayalam-composable-pattern
-  (concat
-   "\\([അ-ഔ][ം]?\\)\\|ഃ"
-   "\\|\\("
-   "\\(?:\\(?:[ക-ഹ]്\\)?\\(?:[ക-ഹ]്\\)?\\(?:[ക-ഹ]്\\)?[ക-ഹ]്\\)?"
-   "[ക-ഹ]\\(?:്\\|[ാ-ൃെേൈൊൊോൌ]?[ം്]?\\)?"
-   "\\)")
+  (let ((table '(("V" . "[\u0D05-\u0D14\u0D60-\u0D61]") ; independent vowel
+		 ("C" . "[\u0D15-\u0D39]")		; consonant 
+		 ("m" . "[\u0D46-\u0D48\u0D4A-\u0D4C]")	; prebase matra
+		 ("p" . "[\u0D3E-\u0D44\u0D57]") ; postname matra
+		 ("b" . "[\u0D62-\u0D63]")	 ; belowbase matra
+		 ("a" . "[\u0D02-\u0D03]")	 ; abovebase sign
+		 ("H" . "്")			 ; virama sign 
+		 ("N" . "\u200D")		 ; ZWJ
+		 ("J" . "\u200C")		 ; ZWNJ
+		 ("X" . "[\u0D00-\u0D7F]")))) ; all coverage
+    (indian-compose-regexp
+     (concat
+      ;; consonant-based syllables
+      "\\(CJ?HJ?\\)*C\\(H[NJ]?\\|m?b?p?a?\\)\\|"
+      ;; syllables with an independent vowel
+      "V\\(J?HC\\)?m?b?p?n?a?\\|"
+      ;; special consonant form
+      "JHC\\|"
+      ;; any other singleton characters
+      "X")
+     table))
   "Regexp matching a composable sequence of Malayalam characters.")
 
 (let ((script-regexp-alist
@@ -173,7 +197,7 @@ South Indian language Malayalam is supported in this language environment."))
 	 (tamil . "[\xB80-\xBFF\x200C\x200D]+")
 	 (telugu . "[\xC00-\xC7F\x200C\x200D]+")
 	 (kannada . "[\xC80-\xCFF\x200C\x200D]+")
-	 (malayalam . "[\xD00-\xD7F\x200C\x200D]+"))))
+	 (malayalam . ,malayalam-composable-pattern))))
   (map-char-table
    #'(lambda (key val)
        (let ((slot (assq val script-regexp-alist)))