marcandre	2012-11-07 02:16:44 +0900 (Wed, 07 Nov 2012)

  New Revision: 37524

  http://svn.ruby-lang.org/cgi-bin/viewvc.cgi?view=rev&revision=37524

  Log:
    * enumerator.c: Add support for lazy.drop.size
      [Feature #6636]

  Modified files:
    trunk/enumerator.c
    trunk/test/ruby/test_lazy_enumerator.rb

Index: enumerator.c
===================================================================
--- enumerator.c	(revision 37523)
+++ enumerator.c	(revision 37524)
@@ -1674,6 +1674,19 @@
 }
 
 static VALUE
+lazy_drop_size(VALUE lazy) {
+    long len = NUM2LONG(RARRAY_PTR(rb_ivar_get(lazy, id_arguments))[0]);
+    VALUE receiver = lazy_receiver_size(lazy);
+    if (NIL_P(receiver))
+	return receiver;
+    if (FIXNUM_P(receiver)) {
+	len = FIX2LONG(receiver) - len;
+	return LONG2FIX(len < 0 ? 0 : len);
+    }
+    return rb_funcall(receiver, '-', 1, LONG2NUM(len));
+}
+
+static VALUE
 lazy_drop_func(VALUE val, VALUE args, int argc, VALUE *argv)
 {
     NODE *memo = RNODE(args);
@@ -1699,7 +1712,7 @@
     memo = NEW_MEMO(0, 0, len);
     return lazy_set_method(rb_block_call(rb_cLazy, id_new, 1, &obj,
 					 lazy_drop_func, (VALUE) memo),
-			   rb_ary_new3(1, n), 0);
+			   rb_ary_new3(1, n), lazy_drop_size);
 }
 
 static VALUE
Index: test/ruby/test_lazy_enumerator.rb
===================================================================
--- test/ruby/test_lazy_enumerator.rb	(revision 37523)
+++ test/ruby/test_lazy_enumerator.rb	(revision 37524)
@@ -341,5 +341,10 @@
     assert_equal 3, lazy.take(4).size
     assert_equal 4, loop.lazy.take(4).size
     assert_equal nil, lazy.select{}.take(4).size
+
+    assert_equal 1, lazy.drop(2).size
+    assert_equal 0, lazy.drop(4).size
+    assert_equal Float::INFINITY, loop.lazy.drop(4).size
+    assert_equal nil, lazy.select{}.drop(4).size
   end
 end

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