Adding missing length<=? (closes #909).

lib/scheme/rlist.sld

@@ -39,6 +39,7 @@
           (rename list rlist)
           (rename make-list make-rlist)
           (rename length rlength)
+          (rename length<=? rlength<=?)
           (rename append rappend)
           (rename reverse rreverse)
           (rename list-tail rlist-tail)

lib/srfi/101.scm

@@ -338,6 +338,13 @@
         (+ (kons-size ls) (recr (kons-rest ls)))
         0)))
 
+(define (ra:length<=? ls k)
+  (let lp ((ls ls) (k k))
+    (if (positive? k)
+        (and (ra:pair? ls)
+             (lp (ra:cdr ls) (- k 1)))
+        #t)))
+
 (define (make-foldl empty? first rest)
   (letrec ((f (lambda (cons empty ls)
                 (if (empty? ls) 

lib/srfi/101.sld

@@ -44,6 +44,7 @@
           (rename ra:list list)
           (rename ra:make-list make-list)
           (rename ra:length length)
+          (rename ra:length<=? length<=?)
           (rename ra:append append)
           (rename ra:reverse reverse)
           (rename ra:list-tail list-tail)

lib/srfi/101/test.sld

@@ -79,6 +79,10 @@
       (test 3 (length (list 'a 'b 'c)))
       (test 3 (length (list 'a (list 'b) (list 'c))))
       (test 0 (length '()))
+      (test #t (length<=? 'not-a-list 0))
+      (test #t (length<=? '(a . b) 0))
+      (test #t (length<=? '(a . b) 1))
+      (test #f (length<=? '(a . b) 2))
 
       ;; append
       (test (list 'x 'y) (append (list 'x) (list 'y)))