diff --git a/tk/listlogic.scm b/tk/listlogic.scm
index 885e51f..5e11bbe 100644
--- a/tk/listlogic.scm
+++ b/tk/listlogic.scm
@@ -18,6 +18,17 @@
 ;;the entries in that list are 'unwrapped'. This occurs recursively.
 (define (flatten lst) (flatten-helper lst '() '()))
 
+;; A flat cons. Normal cons returns a list with a nested association in the
+;;car position if x is a list, this function eliminates that assocation,
+;;recursively "flattening" x and combining it's cdr with y.
+(define (fcons x y)
+  (cond ((pair? x)
+         (fcons (car x) (fcons (cdr x) y)))
+        ((null? x)
+         y)
+        (else
+         (cons x y))))
+
 ;; Evaluates (p (car ls1) (car ls2)) and accumulate into a return list as long
 ;;as that evauluation results in #t.
 (define (lp& p ls1 ls2)