-(defun concatenate-two (string1 string2)
- (let* ((len1 (length string1))
- (len2 (length string2))
- (string (make-array (+ len1 len2) :element-type 'character))
- (i 0))
- (dotimes (j len1)
- (aset string i (char string1 j))
- (incf i))
- (dotimes (j len2)
- (aset string i (char string2 j))
- (incf i))
- string))
+
+(defun concat (&rest strs)
+ (flet ((concat-two (str1 str2)
+ (concatenate-storage-vector str1 str2)))
+ (!reduce #'concat-two strs "")))
+
+
+(defun string-upcase (string)
+ (let ((new (make-string (length string))))
+ (dotimes (i (length string) new)
+ (aset new i (char-upcase (char string i))))))
+
+(defun string-downcase (string)
+ (let ((new (make-string (length string))))
+ (dotimes (i (length string) new)
+ (aset new i (char-downcase (char string i))))))