Introduce new function for removing paired delimiters from string.

* lisp/org-macs.el (org-unbracket-string): New function.
* lisp/ob-core.el (org-babel-strip-quotes):
* lisp/ob-lua.el (org-babel-lua-read-string):
* lisp/ox-beamer.el (org-beamer--normalize-argument): Use it.

lisp/ob-core.el

@@ -3084,10 +3084,7 @@ Callers of this function will probably want to add an entry to
 
 (defun org-babel-strip-quotes (string)
   "Strip \\\"s from around a string, if applicable."
-  (if (and (string-prefix-p "\"" string)
-	   (string-suffix-p "\"" string))
-      (substring string 1 -1)
-    string))
+  (org-unbracket-string "\"" "\"" string))
 
 (provide 'ob-core)
 

lisp/ob-lua.el

@@ -394,9 +394,7 @@ fd:close()"
 
 (defun org-babel-lua-read-string (string)
   "Strip 's from around Lua string."
-  (if (string-match "^'\\([^\000]+\\)'$" string)
-      (match-string 1 string)
-    string))
+  (org-unbracket-string "'" "'" string))
 
 (provide 'ob-lua)
 

lisp/org-macs.el

@@ -285,6 +285,16 @@ the value in cdr."
   "Load FILE with optional arguments NOERROR and MUSTSUFFIX."
   `(load ,file 'noerror nil nil 'mustsuffix))
 
+(defun org-unbracket-string (pre post string)
+  "Remove PRE/POST from the beginning/end of STRING.
+
+Both PRE and POST must be pre-/suffixes of STRING, or neither is
+removed."
+  (if (and (string-prefix-p pre string)
+	   (string-suffix-p post string))
+      (string-remove-prefix pre (string-remove-suffix post string))
+    string))
+
 (provide 'org-macs)
 
 ;;; org-macs.el ends here

lisp/ox-beamer.el

@@ -203,18 +203,13 @@ TYPE is a symbol among the following:
 `option'    Return ARGUMENT within square brackets."
   (if (not (string-match "\\S-" argument)) ""
     (cl-case type
-      (action (if (string-match "\\`<.*>\\'" argument) argument
-		(format "<%s>" argument)))
-      (defaction (cond
-		  ((string-match "\\`\\[<.*>\\]\\'" argument) argument)
-		  ((string-match "\\`<.*>\\'" argument)
-		   (format "[%s]" argument))
-		  ((string-match "\\`\\[\\(.*\\)\\]\\'" argument)
-		   (format "[<%s>]" (match-string 1 argument)))
-		  (t (format "[<%s>]" argument))))
-      (option (if (string-match "\\`\\[.*\\]\\'" argument) argument
-		(format "[%s]" argument)))
-      (otherwise argument))))
+      (action (format "<%s>" (org-unbracket-string "<" ">" argument)))
+      (defaction
+	(format "[<%s>]"
+		(org-unbracket-string "<" ">" (org-unbracket-string "[" "]" argument))))
+      (option (format "[%s]" (org-unbracket-string "[" "]" argument)))
+      (otherwise (error "Invalid `type' argument to `org-beamer--normalize-argument': %s"
+			type)))))
 
 (defun org-beamer--element-has-overlay-p (element)
   "Non-nil when ELEMENT has an overlay specified.