1 files changed, 19 insertions, 0 deletions
diff --git a/src/util.lisp b/src/util.lisp
index 027a770..93db659 100644
--- a/src/util.lisp
+++ b/src/util.lisp
@@ -11,6 +11,25 @@
   (declare (type (integer 0 *) len))
   (format nil "~V,'0b" len num))
 
+(defun insert-in-middle (list element)
+  (append (list (car list)) (list element) (cdr list)))
+
+(defun iota (n)
+  "Generates a number sequence from 0 to N."
+  (when (> n 0)
+    (do ((i 0 (1+ i))
+	 (item 0 (1+ item))
+	 (result nil (push item result)))
+	((= i n) (nreverse result)))))
+
+(defun riffle (lst1 lst2)
+  "Given LST1 and LST2, returns a new list which is the an alternative sequence
+of the elements from both lists. Returns nil if the lists are not equal size."
+  (when (eq (length lst1) (length lst2))
+    (loop for l1 in lst1
+	  for l2 in lst2
+	  append (list l1 l2))))
+
 (defparameter type-r
   '(ADD SUB MUL QUOT REM SFTR SFTL AND OR NOT XOR ADDV SUBV MULV DIVV CMP CEV)
   "R-type instructions.")