* move flatten' next to append*'

* document `add-between'

svn: r9369

collects/scheme/list.ss

@@ -13,8 +13,8 @@
          take
 
          append*
-         add-between
-         flatten)
+         flatten
+         add-between)
 
 (define (first x)
   (if (and (pair? x) (list? x))
@@ -78,6 +78,12 @@
   (case-lambda [(ls) (apply append ls)] ; optimize common case
                [(l . lss) (apply append (apply list* l lss))]))
 
+(define (flatten orig-sexp)
+  (let loop ([sexp orig-sexp] [acc null])
+    (cond [(null? sexp) acc]
+          [(pair? sexp) (loop (car sexp) (loop (cdr sexp) acc))]
+          [else (cons sexp acc)])))
+
 ;; General note: many non-tail recursive, which are just as fast in mzscheme
 
 (define (add-between l x)
@@ -101,9 +107,3 @@
 ;;                         (if (null? ls)
 ;;                           ls
 ;;                           (append l (car ls) (loop (cdr ls))))))]))
-
-(define (flatten orig-sexp)
-  (let loop ([sexp orig-sexp] [acc null])
-    (cond [(null? sexp) acc]
-          [(pair? sexp) (loop (car sexp) (loop (cdr sexp) acc))]
-          [else (cons sexp acc)])))

collects/scribblings/reference/pairs.scrbl

@@ -529,6 +529,16 @@ must merely start with a chain of at least @scheme[pos] pairs.
  (take 'non-list 0)
 ]}
 
+@defproc[(add-between [lst list?] [v any/c]) list?]{
+
+Returns a list that is made of items from @scheme[lst], with
+@scheme[v] between each two items.
+
+@examples[#:eval list-eval
+  (add-between '(x y z) 'or)
+  (add-between '(x) 'or)
+]}
+
 @defproc*[([(append* [lst list?] ... [lsts (listof list?)]) list?]
            [(append* [lst list?] ... [lsts list?]) any/c])]{
 @; Note: this is exactly the same description as the one for string-append*

collects/tests/mzscheme/list.ss

@@ -183,13 +183,6 @@
   (test '(0 1 0 2 0 3) append* (map (lambda (x) (list 0 x)) '(1 2 3)))
   (test '(1 2 3 4 5 6 7 8 9) append* '(1 2 3) '(4 5) '((6 7 8) (9))))
 
-;; ---------- add-between ----------
-(let ()
-  (test '()          add-between '() 1)
-  (test '(9)         add-between '(9) 1)
-  (test '(9 1 8 1 7) add-between '(9 8 7) 1)
-  (test '(9 (1) 8)   add-between '(9 8) '(1)))
-
 ;; ---------- flatten ----------
 (let ()
   (define (all-sexps n)
@@ -201,4 +194,11 @@
   (define (flat? x) (and (list? x) (andmap (lambda (x) (eq? 'x x)) x)))
   (for ([x sexps]) (test #t flat? (flatten x))))
 
+;; ---------- add-between ----------
+(let ()
+  (test '()          add-between '() 1)
+  (test '(9)         add-between '(9) 1)
+  (test '(9 1 8 1 7) add-between '(9 8 7) 1)
+  (test '(9 (1) 8)   add-between '(9 8) '(1)))
+
 (report-errs)