Added (flatten lst) and guile module definition

tk/listlogic.scm

@@ -1,3 +1,21 @@
+(define-module (tk listlogic)
+  #:export ('flatten
+            'lp&
+            'l&
+            )
+  #:duplicates (warn-override-core warn ))
+
+(define (flatten-helper lst acc stk)
+  (cond ((null? lst)
+         (if (null? stk) (reverse acc)
+             (flatten-helper (car stk) acc (cdr stk))))
+        ((pair? (car lst))
+         (flatten-helper (car lst) acc (cons (cdr lst) stk)))
+        (else
+         (flatten-helper (cdr lst) (cons (car lst) acc) stk))))
+
+(define (flatten lst) (flatten-helper lst '() '()))
+
 (define (lp& p ls1 ls2)
   (let loop ((ls1 ls1) (ls2 ls2))
     (cond ((not (and (pair? ls1) (pair? ls2)))
@@ -7,8 +25,6 @@
           (else '())
           )))
 
-(define (ls& ls1 ls2)
+(define (l& ls1 ls2)
   (cond ((eqv? ls1 ls2) ls1)
         (else (lp& eqv? ls1 ls2))))
-
-