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-- Copyright (c) 1991-2002, The Numerical ALgorithms Group Ltd.
-- All rights reserved.
-- Copyright (C) 2007-2012, Gabriel Dos Reis.
-- All rights reserved.
--
-- Redistribution and use in source and binary forms, with or without
-- modification, are permitted provided that the following conditions are
-- met:
--
-- - Redistributions of source code must retain the above copyright
-- notice, this list of conditions and the following disclaimer.
--
-- - 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.
--
-- - Neither the name of The Numerical ALgorithms Group Ltd. nor the
-- names of its contributors may be used to endorse or promote products
-- derived from this software without specific prior written permission.
--
-- THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "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 COPYRIGHT OWNER
-- OR 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.
import sys_-macros
namespace BOOT
termRW(t,R) ==
-- reduce t by rewrite system R
until b repeat
t0:= termRW1(t,R)
b:= sameObject?(t,t0)
t:= t0
t
termRW1(t,R) ==
-- tries to do one reduction on the leftmost outermost subterm of t
t0:= term1RW(t,R)
not sameObject?(t0,t) or t isnt [.,:.] => t0
[t1,:t2]:= t
tt1:= termRW1(t1,R)
tt2:= t2 and termRW1(t2,R)
sameObject?(t1,tt1) and sameObject?(t2,tt2) => t
[tt1,:tt2]
term1RW(t,R) ==
-- tries to reduce t at the top node
[vars,:varRules]:= R
for r in varRules until not (SL='failed) repeat
SL:= termMatch(first r,t,nil,vars)
not (SL='failed) =>
t:= subCopy(copy rest r,SL)
t
term1RWall(t,R) ==
-- same as term1RW, but returns a list
[vars,:varRules]:= R
[not (SL='failed) and subCopy(copy rest r,SL) for r in varRules |
not sameObject?(SL:= termMatch(first r,t,nil,vars),'failed)]
termMatch(tp,t,SL,vars) ==
-- t is a term pattern, t a term
-- then the result is the augmented substitution SL or 'failed
tp=t => SL
tp isnt [.,:.] =>
symbolMember?(tp,vars) =>
p:= ASSOC(tp,SL) => ( rest p=t )
[[tp,:t],:SL]
'failed
t isnt [.,:.] => 'failed
[tp1,:tp2]:= tp
[t1,:t2]:= t
SL:= termMatch(tp1,t1,SL,vars)
SL='failed => 'failed
tp2 and t2 => termMatch(tp2,t2,SL,vars)
tp2 or t2 => 'failed
SL
--% substitution handling
-- isContained(v,t) ==
-- -- tests (by EQ), whether v occurs in term t
-- -- v must not be nil
-- sameObject?(v,t) => 'T
-- t isnt [.,:.] => nil
-- isContained(v,first t) or isContained(v,rest t)
augmentSub(v,t,SL) ==
-- destructively adds the pair (v,t) to the substitution list SL
-- t doesn't contain any of the variables of SL
q := [v,:t]
null SL => [q]
-- for p in SL repeat p.rest := substitute(t,v,rest p)
[q,:SL]
mergeSubs(S1,S2) ==
-- augments S2 by each pair of S1
-- S1 doesn't contain any of the variables of S2
null S1 => S2
null S2 => S1
S3 := [p for p in S2 | objectAssoc(first p, S1) = nil]
-- for p in S1 repeat S3:= augmentSub(first p,rest p,S3)
append(S1,S3)
subCopy(t,SL) ==
-- t is any LISP structure, SL a substitution list for sharp variables
-- then t is substituted and copied if necessary
SL=nil => t
subCopy0(t,SL)
subCopy0(t, SL) ==
p := subCopyOrNil(t, SL) => rest p
t
subCopyOrNil(t,SL) ==
-- the same as subCopy, but the result is nil if nothing was copied
p:= ASSOC(t,SL) => p
t isnt [.,:.] => nil
[t1,:t2]:= t
t0:= subCopyOrNil(t1,SL) =>
t2 => [t, :[rest t0,:subCopy0(t2,SL)]]
[t,:[rest t0,:t2]]
t2 and ( t0:= subCopyOrNil(t2,SL) ) => [t, :[t1,:rest t0]]
nil
deepSubCopy(t,SL) ==
-- t is any LISP structure, SL a substitution list for sharp variables
-- then t is substituted and copied if necessary
SL=nil => t
deepSubCopy0(t,SL)
deepSubCopy0(t, SL) ==
p := deepSubCopyOrNil(t, SL) => rest p
t
deepSubCopyOrNil(t,SL) ==
-- the same as subCopy, but the result is nil if nothing was copied
p:= ASSOC(t,SL) => [t,:deepSubCopy0(rest p, SL)]
t isnt [.,:.] => nil
[t1,:t2]:= t
t0:= deepSubCopyOrNil(t1,SL) =>
t2 => [t, :[rest t0,:deepSubCopy0(t2,SL)]]
[t,:[rest t0,:t2]]
t2 and ( t0:= deepSubCopyOrNil(t2,SL) ) => [t,:[t1,:rest t0]]
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