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Diffstat (limited to 'src/theory/booleans/theory_bool.cpp')
-rw-r--r-- | src/theory/booleans/theory_bool.cpp | 146 |
1 files changed, 146 insertions, 0 deletions
diff --git a/src/theory/booleans/theory_bool.cpp b/src/theory/booleans/theory_bool.cpp new file mode 100644 index 000000000..a7e343fdc --- /dev/null +++ b/src/theory/booleans/theory_bool.cpp @@ -0,0 +1,146 @@ +/********************* */ +/*! \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 */ |