add dup

1 files changed, 17 insertions, 1 deletions

diff --git a/mew.scm b/mew.scm
index 259f51c..8635195 100644
--- a/mew.scm
+++ b/mew.scm
@@ -3,7 +3,7 @@
      act accumulate andloc app at
      boolean
      comp cross-product
-     dec def del-at div
+     dec def del-at div dup
      empty? eof esc
      fail fin final for fun*
      gconcatenate gen generator-xfold generic-for-each genumerate get
@@ -395,6 +395,22 @@
           ((procedure? o) (generator-count (op #t) o))
           (#t (error "no len defined"))))
 
+  (define dup
+    (case-lambda
+      ((o) (dup o #t))
+      ((o depth)
+       (if (or (eq? depth #t) (positive? depth))
+         (let ((sub-depth (or (eq? depth #t) (- depth 1))))
+           (cond ((list? o) (map (lambda (oo) (dup oo sub-depth)) o))
+                 ((vector? o) (vector-map (lambda (oo) (dup oo sub-depth)) o))
+                 ((hash-table? o)
+                  (alist->hash-table (dup (hash-table->alist o) sub-depth)
+                                     (hash-table-equivalence-function o)
+                                     (hash-table-hash-function o)))
+                 ((string? o) (string-copy o))
+                 (else o)))
+         o))))
+
   (define (generic-for-each obj)
     (cond ((list? obj) for-each)
           ((vector? obj) vector-for-each)