--- /dev/null
+! :folding=indent:collapseFolds=1:
+
+! $Id$
+!
+! Copyright (C) 2004 Slava Pestov.
+!
+! Redistribution and use in source and binary forms, with or without
+! modification, are permitted provided that the following conditions are met:
+!
+! 1. Redistributions of source code must retain the above copyright notice,
+! this list of conditions and the following disclaimer.
+!
+! 2. Redistributions in binary form must reproduce the above copyright notice,
+! this list of conditions and the following disclaimer in the documentation
+! and/or other materials provided with the distribution.
+!
+! THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES,
+! INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
+! FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+! DEVELOPERS AND CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+! SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+! PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
+! OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
+! WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
+! OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
+! ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+IN: kernel
+USE: vectors
+
+: 2drop ( x x -- ) drop drop ; inline
+: 3drop ( x x x -- ) drop drop drop ; inline
+: 2dup ( x y -- x y x y ) over over ; inline
+: 3dup ( x y z -- x y z x y z ) pick pick pick ; inline
+: rot ( x y z -- y z x ) >r swap r> swap ; inline
+: -rot ( x y z -- z x y ) swap >r swap r> ; inline
+: dupd ( x y -- x x y ) >r dup r> ; inline
+: swapd ( x y z -- y x z ) >r swap r> ; inline
+: nip ( x y -- y ) swap drop ; inline
+: tuck ( x y -- y x y ) dup >r swap r> ; inline
+
+: clear ( -- )
+ #! Clear the datastack. For interactive use only; invoking
+ #! this from a word definition will clobber any values left
+ #! on the data stack by the caller.
+ { } set-datastack ;
+
+: depth ( -- n )
+ #! Push the number of elements on the datastack.
+ datastack vector-length ;