\ Copyright 2023 Bradley D. Nelson
\
\ Licensed under the Apache License, Version 2.0 (the "License");
\ you may not use this file except in compliance with the License.
\ You may obtain a copy of the License at
\
\     http://www.apache.org/licenses/LICENSE-2.0
\
\ Unless required by applicable law or agreed to in writing, software
\ distributed under the License is distributed on an "AS IS" BASIS,
\ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
\ See the License for the specific language governing permissions and
\ limitations under the License.

needs ../oofda.fs

class Stack
  variable start
  variable sp
  : .construct ( n -- ) here start ! here sp ! cells allot ;
  : .empty? ( -- f ) sp @ start @ = ;
  : .push ( n -- ) sp @ ! cell sp +! ;
  : .pop ( -- n ) this .empty? throw
                  cell negate sp +! sp @ @ ;
end-class