concat now accepts an arbitrary number of arguments.

collections/sequences.lisp

@@ -136,13 +136,21 @@
 ;;; concat
 ;;; ---------------------------------------------------------------------
 
-(defmethod concat (s0 s1)
+(defmethod %concat (s0 s1)
   (concatenate (classname-for-sequence s0)
                s0 (as (classname-for-sequence s0) s1)))
 
-(defmethod concat ((s0 fset:seq) s1)
+(defmethod %concat ((s0 fset:seq) s1)
   (fset:concat s0 (as 'fset:seq s1)))
 
+(defun concat (&rest sequences)
+  (if (null sequences)
+      nil
+      (if (null (cdr sequences))
+          (car sequences)
+          (reduce #'%concat (cddr sequences) :initial-value (%concat (car sequences)
+                                                                     (cadr sequences))))))
+
 ;;; ---------------------------------------------------------------------
 ;;; contains?
 ;;; ---------------------------------------------------------------------

doc/collections/sequences.txt

@@ -31,12 +31,12 @@ CHOOSE-ANY (s) => val
 
   CHOOSE-ANY returns a randomly-chosen element of S.
 
-CONCAT (s1 s2) => new-s
-  generic function
+CONCAT (&rest sequences) => new-sequence
+  function
 
-  CONCAT returns a new sequence of the same class as (or a superclass
-  of) S1, whose elements are the elements of S1 followed by the
-  elements of S2.
+  CONCAT returns a new sequence whose elements are the elements of S1
+  followed by the elements of S2. The type of the result sequence is
+  the same as the type of the first argument sequence.
 
 
 CONTAINS? (s1 x &key (test 'eql)) => boolean