\ Copyright 2021 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.

( Interpret time conditionals )

: DEFINED? ( "name" -- xt|0 )
   bl parse find state @ if aliteral then ; immediate
defer [SKIP]
: [THEN] ;   : [ELSE] [SKIP] ;   : [IF] 0= if [SKIP] then ;
: [SKIP]' 0 begin postpone defined? dup if
    dup ['] [IF] = if swap 1+ swap then
    dup ['] [ELSE] = if swap dup 0 <= if 2drop exit then swap then
    dup ['] [THEN] = if swap 1- dup 0< if 2drop exit then swap then
  then drop again ;
' [SKIP]' is [SKIP]