added string functions

stdlib/stdlib.lsp

@@ -24,16 +24,17 @@
 (defun string-trim (str) 
     (string-rltrim str " \n\r\t" "trim"))
 
-; pad string on the end
 (defun string-rpad (str length pad_char)
     (string-pad str length pad_char "rpad"))
-
-; pad string on the begining
 (defun string-lpad (str length pad_char)
     (string-pad str length pad_char "lpad"))
 
+(defun string-upcase (str) 
+    (string-case str "upper"))
+(defun string-downcase (str) 
+    (string-case str "lower"))
 
-; pause for interval
+; pause for interval of seconds
 (defun sleep (time) 
   (system-cmd (+ "sleep " (string time))))