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/********************* */
/*! \file theory_bool.cpp
** \verbatim
** Original author: mdeters
** Major contributors: none
** Minor contributors (to current version): none
** This file is part of the CVC4 prototype.
** Copyright (c) 2009, 2010 The Analysis of Computer Systems Group (ACSys)
** Courant Institute of Mathematical Sciences
** New York University
** See the file COPYING in the top-level source directory for licensing
** information.\endverbatim
**
** \brief The theory of booleans.
**
** The theory of booleans.
**/
#include "theory/theory.h"
#include "theory/booleans/theory_bool.h"
namespace CVC4 {
namespace theory {
namespace booleans {
RewriteResponse TheoryBool::preRewrite(TNode n, bool topLevel) {
if(n.getKind() == kind::IFF) {
NodeManager* nodeManager = NodeManager::currentNM();
Node tt = nodeManager->mkConst(true);
Node ff = nodeManager->mkConst(false);
// rewrite simple cases of IFF
if(n[0] == tt) {
// IFF true x
return RewriteAgain(n[1]);
} else if(n[1] == tt) {
// IFF x true
return RewriteAgain(n[0]);
} else if(n[0] == ff) {
// IFF false x
return RewriteAgain(n[1].notNode());
} else if(n[1] == ff) {
// IFF x false
return RewriteAgain(n[0].notNode());
} else if(n[0] == n[1]) {
// IFF x x
return RewriteComplete(tt);
} else if(n[0].getKind() == kind::NOT && n[0][0] == n[1]) {
// IFF (NOT x) x
return RewriteComplete(ff);
} else if(n[1].getKind() == kind::NOT && n[1][0] == n[0]) {
// IFF x (NOT x)
return RewriteComplete(ff);
}
} else if(n.getKind() == kind::ITE) {
// non-Boolean-valued ITEs should have been removed in place of
// a variable
Assert(n.getType().isBoolean());
NodeManager* nodeManager = NodeManager::currentNM();
// rewrite simple cases of ITE
if(n[0] == nodeManager->mkConst(true)) {
// ITE true x y
return RewriteAgain(n[1]);
} else if(n[0] == nodeManager->mkConst(false)) {
// ITE false x y
return RewriteAgain(n[2]);
} else if(n[1] == n[2]) {
// ITE c x x
return RewriteAgain(n[1]);
}
}
return RewriteComplete(n);
}
RewriteResponse TheoryBool::postRewrite(TNode n, bool topLevel) {
if(n.getKind() == kind::IFF) {
NodeManager* nodeManager = NodeManager::currentNM();
Node tt = nodeManager->mkConst(true);
Node ff = nodeManager->mkConst(false);
// rewrite simple cases of IFF
if(n[0] == tt) {
// IFF true x
return RewriteComplete(n[1]);
} else if(n[1] == tt) {
// IFF x true
return RewriteComplete(n[0]);
} else if(n[0] == ff) {
// IFF false x
return RewriteAgain(n[1].notNode());
} else if(n[1] == ff) {
// IFF x false
return RewriteAgain(n[0].notNode());
} else if(n[0] == n[1]) {
// IFF x x
return RewriteComplete(tt);
} else if(n[0].getKind() == kind::NOT && n[0][0] == n[1]) {
// IFF (NOT x) x
return RewriteComplete(ff);
} else if(n[1].getKind() == kind::NOT && n[1][0] == n[0]) {
// IFF x (NOT x)
return RewriteComplete(ff);
}
if(n[1] < n[0]) {
// normalize (IFF x y) ==> (IFF y x), if y < x
return RewriteComplete(n[1].iffNode(n[0]));
}
} else if(n.getKind() == kind::ITE) {
// non-Boolean-valued ITEs should have been removed in place of
// a variable
Assert(n.getType().isBoolean());
NodeManager* nodeManager = NodeManager::currentNM();
// rewrite simple cases of ITE
if(n[0] == nodeManager->mkConst(true)) {
// ITE true x y
return RewriteComplete(n[1]);
} else if(n[0] == nodeManager->mkConst(false)) {
// ITE false x y
return RewriteComplete(n[2]);
} else if(n[1] == n[2]) {
// ITE c x x
return RewriteComplete(n[1]);
}
if(n[0].getKind() == kind::NOT) {
// rewrite (ITE (NOT c) x y) to (ITE c y x)
Node out = nodeManager->mkNode(kind::ITE, n[0][0], n[2], n[1]);
return RewriteComplete(out);
}
}
return RewriteComplete(n);
}
}/* CVC4::theory::booleans namespace */
}/* CVC4::theory namespace */
}/* CVC4 namespace */
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