30 lines
1.1 KiB
Forth
30 lines
1.1 KiB
Forth
\ Copyright 2021 Bradley D. Nelson
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\
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\ Licensed under the Apache License, Version 2.0 (the "License");
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\ you may not use this file except in compliance with the License.
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\ You may obtain a copy of the License at
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\
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\ http://www.apache.org/licenses/LICENSE-2.0
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\
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\ Unless required by applicable law or agreed to in writing, software
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\ distributed under the License is distributed on an "AS IS" BASIS,
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\ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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\ See the License for the specific language governing permissions and
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\ limitations under the License.
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( Interpret time conditionals )
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: DEFINED? ( "name" -- xt|0 )
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begin bl parse dup 0= while 2drop refill 0= throw repeat
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find state @ if aliteral then ; immediate
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defer [SKIP]
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: [THEN] ; immediate
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: [ELSE] [SKIP] ; immediate
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: [IF] 0= if [SKIP] then ; immediate
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: [SKIP]' 0 begin postpone defined? dup if
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dup ['] [IF] = if swap 1+ swap then
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dup ['] [ELSE] = if swap dup 0 <= if 2drop exit then swap then
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dup ['] [THEN] = if swap 1- dup 0< if 2drop exit then swap then
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then drop again ;
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' [SKIP]' is [SKIP]
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