Head

GCC Code Coverage Report

Directory:	.		Exec	Total	Coverage
File:	src/theory/strings/skolem_cache.cpp	Lines:	127	139	91.4 %
Date:	2021-09-29	Branches:	288	589	48.9 %


/******************************************************************************
 * Top contributors (to current version):
 *   Andrew Reynolds, Andres Noetzli, Yoni Zohar
 *
 * This file is part of the cvc5 project.
 *
 * Copyright (c) 2009-2021 by the authors listed in the file AUTHORS
 * in the top-level source directory and their institutional affiliations.
 * All rights reserved.  See the file COPYING in the top-level source
 * directory for licensing information.
 * ****************************************************************************
 *
 * Implementation of a cache of skolems for theory of strings.
 */

#include "theory/strings/skolem_cache.h"

#include "expr/attribute.h"
#include "expr/bound_var_manager.h"
#include "expr/skolem_manager.h"
#include "theory/rewriter.h"
#include "theory/strings/arith_entail.h"
#include "theory/strings/theory_strings_utils.h"
#include "theory/strings/word.h"
#include "util/rational.h"

using namespace cvc5::kind;

namespace cvc5 {
namespace theory {
namespace strings {

/**
 * A bound variable corresponding to the universally quantified integer
 * variable used to range over the valid positions in a string, used
 * for axiomatizing the behavior of some term.
 */
struct IndexVarAttributeId
{
};
typedef expr::Attribute<IndexVarAttributeId, Node> IndexVarAttribute;

/**
 * A bound variable corresponding to the universally quantified integer
 * variable used to range over the valid lengths of a string, used for
 * axiomatizing the behavior of some term.
 */
struct LengthVarAttributeId
{
};
typedef expr::Attribute<LengthVarAttributeId, Node> LengthVarAttribute;

SkolemCache::SkolemCache(bool useOpts) : d_useOpts(useOpts)
{
  NodeManager* nm = NodeManager::currentNM();
  d_strType = nm->stringType();
  d_zero = nm->mkConst(Rational(0));
}

Node SkolemCache::mkSkolemCached(Node a, Node b, SkolemId id, const char* c)
{
  return mkTypedSkolemCached(d_strType, a, b, id, c);
}

Node SkolemCache::mkSkolemCached(Node a, SkolemId id, const char* c)
{
  return mkSkolemCached(a, Node::null(), id, c);
}

Node SkolemCache::mkTypedSkolemCached(
    TypeNode tn, Node a, Node b, SkolemId id, const char* c)
{
  Trace("skolem-cache") << "mkTypedSkolemCached start: (" << id << ", " << a
                        << ", " << b << ")" << std::endl;
  SkolemId idOrig = id;
  // do not rewrite beforehand if we are not using optimizations, this is so
  // that the proof checker does not depend on the rewriter.
  if (d_useOpts)
  {
    a = a.isNull() ? a : Rewriter::rewrite(a);
    b = b.isNull() ? b : Rewriter::rewrite(b);
  }
  std::tie(id, a, b) = normalizeStringSkolem(id, a, b);

  // optimization: if we aren't asking for the purification skolem for constant
  // a, and the skolem is equivalent to a, then we just return a.
  if (d_useOpts && idOrig != SK_PURIFY && id == SK_PURIFY && a.isConst())
  {
    Trace("skolem-cache") << "...optimization: return constant " << a
                          << std::endl;
    return a;
  }

  std::map<SkolemId, Node>::iterator it = d_skolemCache[a][b].find(id);
  if (it != d_skolemCache[a][b].end())
  {
    Trace("skolem-cache") << "...return existing " << it->second << std::endl;
    // already cached
    return it->second;
  }

  NodeManager* nm = NodeManager::currentNM();
  SkolemManager* sm = nm->getSkolemManager();
  Node sk;
  switch (id)
  {
    // exists k. k = a
    case SK_PURIFY:
    {
      // for sequences of Booleans, we may purify Boolean terms, in which case
      // they must be Boolean term variables.
      int flags = a.getType().isBoolean() ? NodeManager::SKOLEM_BOOL_TERM_VAR
                                          : NodeManager::SKOLEM_DEFAULT;
      sk = sm->mkPurifySkolem(a, c, "string purify skolem", flags);
    }
    break;
    // these are eliminated by normalizeStringSkolem
    case SK_ID_V_SPT:
    case SK_ID_V_SPT_REV:
    case SK_ID_VC_SPT:
    case SK_ID_VC_SPT_REV:
    case SK_FIRST_CTN_POST:
    case SK_ID_C_SPT:
    case SK_ID_C_SPT_REV:
    case SK_ID_DC_SPT:
    case SK_ID_DC_SPT_REM:
    case SK_ID_DEQ_X:
    case SK_ID_DEQ_Y:
    case SK_FIRST_CTN_PRE:
    case SK_PREFIX:
    case SK_SUFFIX_REM:
      Unhandled() << "Expected to eliminate Skolem ID " << id << std::endl;
      break;
    case SK_NUM_OCCUR:
    case SK_OCCUR_INDEX:
    default:
    {
      Notice() << "Don't know how to handle Skolem ID " << id << std::endl;
      Node v = nm->mkBoundVar(tn);
      Node cond = nm->mkConst(true);
      sk = sm->mkSkolem(v, cond, c, "string skolem");
    }
    break;
  }
  Trace("skolem-cache") << "...returned " << sk << std::endl;
  d_allSkolems.insert(sk);
  d_skolemCache[a][b][id] = sk;
  return sk;
}
Node SkolemCache::mkTypedSkolemCached(TypeNode tn,
                                      Node a,
                                      SkolemId id,
                                      const char* c)
{
  return mkTypedSkolemCached(tn, a, Node::null(), id, c);
}

Node SkolemCache::mkSkolemSeqNth(TypeNode seqType, const char* c)
{
  // Note this method is static and does not rely on any local caching.
  // It is used by expand definitions and by (dynamic) reductions, thus
  // it is centrally located here.
  Assert(seqType.isSequence());
  NodeManager* nm = NodeManager::currentNM();
  SkolemManager* sm = nm->getSkolemManager();
  std::vector<TypeNode> argTypes;
  argTypes.push_back(seqType);
  argTypes.push_back(nm->integerType());
  TypeNode elemType = seqType.getSequenceElementType();
  TypeNode ufType = nm->mkFunctionType(argTypes, elemType);
  return sm->mkSkolemFunction(SkolemFunId::SEQ_NTH_OOB, ufType);
}

Node SkolemCache::mkSkolem(const char* c)
{
  // TODO: eliminate this
  SkolemManager* sm = NodeManager::currentNM()->getSkolemManager();
  Node n = sm->mkDummySkolem(c, d_strType, "string skolem");
  d_allSkolems.insert(n);
  return n;
}

bool SkolemCache::isSkolem(Node n) const
{
  return d_allSkolems.find(n) != d_allSkolems.end();
}

std::tuple<SkolemCache::SkolemId, Node, Node>
SkolemCache::normalizeStringSkolem(SkolemId id, Node a, Node b)
{

  NodeManager* nm = NodeManager::currentNM();

  // eliminate in terms of prefix/suffix_rem
  if (id == SK_FIRST_CTN_POST)
  {
    // SK_FIRST_CTN_POST(x, y) --->
    //   SK_SUFFIX_REM(x, (+ (str.len SK_FIRST_CTN_PRE(x, y)) (str.len y)))
    id = SK_SUFFIX_REM;
    Node pre = mkSkolemCached(a, b, SK_FIRST_CTN_PRE, "pre");
    b = nm->mkNode(
        PLUS, nm->mkNode(STRING_LENGTH, pre), nm->mkNode(STRING_LENGTH, b));
  }
  else if (id == SK_ID_V_SPT || id == SK_ID_C_SPT)
  {
    // SK_ID_*_SPT(x, y) ---> SK_SUFFIX_REM(x, (str.len y))
    id = SK_SUFFIX_REM;
    b = nm->mkNode(STRING_LENGTH, b);
  }
  else if (id == SK_ID_V_SPT_REV || id == SK_ID_C_SPT_REV)
  {
    // SK_ID_*_SPT_REV(x, y) ---> SK_PREFIX(x, (- (str.len x) (str.len y)))
    id = SK_PREFIX;
    b = nm->mkNode(
        MINUS, nm->mkNode(STRING_LENGTH, a), nm->mkNode(STRING_LENGTH, b));
  }
  else if (id == SK_ID_VC_SPT)
  {
    // SK_ID_VC_SPT(x, y) ---> SK_SUFFIX_REM(x, 1)
    id = SK_SUFFIX_REM;
    b = nm->mkConst(Rational(1));
  }
  else if (id == SK_ID_VC_SPT_REV)
  {
    // SK_ID_VC_SPT_REV(x, y) ---> SK_PREFIX(x, (- (str.len x) 1))
    id = SK_PREFIX;
    b = nm->mkNode(
        MINUS, nm->mkNode(STRING_LENGTH, a), nm->mkConst(Rational(1)));
  }
  else if (id == SK_ID_DC_SPT)
  {
    // SK_ID_DC_SPT(x, y) ---> SK_PREFIX(x, 1)
    id = SK_PREFIX;
    b = nm->mkConst(Rational(1));
  }
  else if (id == SK_ID_DC_SPT_REM)
  {
    // SK_ID_DC_SPT_REM(x, y) ---> SK_SUFFIX_REM(x, 1)
    id = SK_SUFFIX_REM;
    b = nm->mkConst(Rational(1));
  }
  else if (id == SK_ID_DEQ_X)
  {
    // SK_ID_DEQ_X(x, y) ---> SK_PREFIX(y, (str.len x))
    id = SK_PREFIX;
    Node aOld = a;
    a = b;
    b = nm->mkNode(STRING_LENGTH, aOld);
  }
  else if (id == SK_ID_DEQ_Y)
  {
    // SK_ID_DEQ_Y(x, y) ---> SK_PREFIX(x, (str.len y))
    id = SK_PREFIX;
    b = nm->mkNode(STRING_LENGTH, b);
  }
  else if (id == SK_FIRST_CTN_PRE)
  {
    // SK_FIRST_CTN_PRE(x,y) ---> SK_PREFIX(x, indexof(x,y,0))
    id = SK_PREFIX;
    b = nm->mkNode(STRING_INDEXOF, a, b, d_zero);
  }

  if (id == SK_ID_V_UNIFIED_SPT || id == SK_ID_V_UNIFIED_SPT_REV)
  {
    bool isRev = (id == SK_ID_V_UNIFIED_SPT_REV);
    Node la = nm->mkNode(STRING_LENGTH, a);
    Node lb = nm->mkNode(STRING_LENGTH, b);
    Node ta = isRev ? utils::mkPrefix(a, nm->mkNode(MINUS, la, lb))
                    : utils::mkSuffix(a, lb);
    Node tb = isRev ? utils::mkPrefix(b, nm->mkNode(MINUS, lb, la))
                    : utils::mkSuffix(b, la);
    id = SK_PURIFY;
    // SK_ID_V_UNIFIED_SPT(x,y) --->
    //   ite(len(x) >= len(y), substr(x,0,str.len(y)), substr(y,0,str.len(x))
    a = nm->mkNode(ITE, nm->mkNode(GEQ, la, lb), ta, tb);
    b = Node::null();
  }

  // now, eliminate prefix/suffix_rem in terms of purify
  if (id == SK_PREFIX)
  {
    // SK_PREFIX(x,y) ---> SK_PURIFY(substr(x,0,y))
    id = SK_PURIFY;
    a = utils::mkPrefix(a, b);
    b = Node::null();
  }
  else if (id == SK_SUFFIX_REM)
  {
    // SK_SUFFIX_REM(x,y) ---> SK_PURIFY(substr(x,y,str.len(x)-y))
    id = SK_PURIFY;
    a = utils::mkSuffix(a, b);
    b = Node::null();
  }

  if (d_useOpts)
  {
    a = a.isNull() ? a : Rewriter::rewrite(a);
    b = b.isNull() ? b : Rewriter::rewrite(b);
  }
  Trace("skolem-cache") << "normalizeStringSkolem end: (" << id << ", " << a
                        << ", " << b << ")" << std::endl;
  return std::make_tuple(id, a, b);
}

Node SkolemCache::mkIndexVar(Node t)
{
  NodeManager* nm = NodeManager::currentNM();
  TypeNode intType = nm->integerType();
  BoundVarManager* bvm = nm->getBoundVarManager();
  return bvm->mkBoundVar<IndexVarAttribute>(t, intType);
}

Node SkolemCache::mkLengthVar(Node t)
{
  NodeManager* nm = NodeManager::currentNM();
  TypeNode intType = nm->integerType();
  BoundVarManager* bvm = nm->getBoundVarManager();
  return bvm->mkBoundVar<LengthVarAttribute>(t, intType);
}

}  // namespace strings
}  // namespace theory
}  // namespace cvc5


Generated by: GCOVR (Version 3.2)

Line	Exec	Source
1		/******************************************************************************
2		* Top contributors (to current version):
3		* Andrew Reynolds, Andres Noetzli, Yoni Zohar
4		*
5		* This file is part of the cvc5 project.
6		*
7		* Copyright (c) 2009-2021 by the authors listed in the file AUTHORS
8		* in the top-level source directory and their institutional affiliations.
9		* All rights reserved. See the file COPYING in the top-level source
10		* directory for licensing information.
11		* ****************************************************************************
12		*
13		* Implementation of a cache of skolems for theory of strings.
14		*/
15
16		#include "theory/strings/skolem_cache.h"
17
18		#include "expr/attribute.h"
19		#include "expr/bound_var_manager.h"
20		#include "expr/skolem_manager.h"
21		#include "theory/rewriter.h"
22		#include "theory/strings/arith_entail.h"
23		#include "theory/strings/theory_strings_utils.h"
24		#include "theory/strings/word.h"
25		#include "util/rational.h"
26
27		using namespace cvc5::kind;
28
29		namespace cvc5 {
30		namespace theory {
31		namespace strings {
32
33		/**
34		* A bound variable corresponding to the universally quantified integer
35		* variable used to range over the valid positions in a string, used
36		* for axiomatizing the behavior of some term.
37		*/
38		struct IndexVarAttributeId
39		{
40		};
41		typedef expr::Attribute<IndexVarAttributeId, Node> IndexVarAttribute;
42
43		/**
44		* A bound variable corresponding to the universally quantified integer
45		* variable used to range over the valid lengths of a string, used for
46		* axiomatizing the behavior of some term.
47		*/
48		struct LengthVarAttributeId
49		{
50		};
51		typedef expr::Attribute<LengthVarAttributeId, Node> LengthVarAttribute;
52
53	6307	SkolemCache::SkolemCache(bool useOpts) : d_useOpts(useOpts)
54		{
55	6307	NodeManager* nm = NodeManager::currentNM();
56	6307	d_strType = nm->stringType();
57	6307	d_zero = nm->mkConst(Rational(0));
58	6307	}
59
60	24977	Node SkolemCache::mkSkolemCached(Node a, Node b, SkolemId id, const char* c)
61		{
62	24977	return mkTypedSkolemCached(d_strType, a, b, id, c);
63		}
64
65	11518	Node SkolemCache::mkSkolemCached(Node a, SkolemId id, const char* c)
66		{
67	11518	return mkSkolemCached(a, Node::null(), id, c);
68		}
69
70	25225	Node SkolemCache::mkTypedSkolemCached(
71		TypeNode tn, Node a, Node b, SkolemId id, const char* c)
72		{
73	50450	Trace("skolem-cache") << "mkTypedSkolemCached start: (" << id << ", " << a
74	25225	<< ", " << b << ")" << std::endl;
75	25225	SkolemId idOrig = id;
76		// do not rewrite beforehand if we are not using optimizations, this is so
77		// that the proof checker does not depend on the rewriter.
78	25225	if (d_useOpts)
79		{
80	25052	a = a.isNull() ? a : Rewriter::rewrite(a);
81	25052	b = b.isNull() ? b : Rewriter::rewrite(b);
82		}
83	25225	std::tie(id, a, b) = normalizeStringSkolem(id, a, b);
84
85		// optimization: if we aren't asking for the purification skolem for constant
86		// a, and the skolem is equivalent to a, then we just return a.
87	25225	if (d_useOpts && idOrig != SK_PURIFY && id == SK_PURIFY && a.isConst())
88		{
89	1106	Trace("skolem-cache") << "...optimization: return constant " << a
90	553	<< std::endl;
91	553	return a;
92		}
93
94	24672	std::map<SkolemId, Node>::iterator it = d_skolemCache[a][b].find(id);
95	24672	if (it != d_skolemCache[a][b].end())
96		{
97	13662	Trace("skolem-cache") << "...return existing " << it->second << std::endl;
98		// already cached
99	13662	return it->second;
100		}
101
102	11010	NodeManager* nm = NodeManager::currentNM();
103	11010	SkolemManager* sm = nm->getSkolemManager();
104	22020	Node sk;
105	11010	switch (id)
106		{
107		// exists k. k = a
108	10896	case SK_PURIFY:
109		{
110		// for sequences of Booleans, we may purify Boolean terms, in which case
111		// they must be Boolean term variables.
112	21792	int flags = a.getType().isBoolean() ? NodeManager::SKOLEM_BOOL_TERM_VAR
113	10896	: NodeManager::SKOLEM_DEFAULT;
114	10896	sk = sm->mkPurifySkolem(a, c, "string purify skolem", flags);
115		}
116	10896	break;
117		// these are eliminated by normalizeStringSkolem
118		case SK_ID_V_SPT:
119		case SK_ID_V_SPT_REV:
120		case SK_ID_VC_SPT:
121		case SK_ID_VC_SPT_REV:
122		case SK_FIRST_CTN_POST:
123		case SK_ID_C_SPT:
124		case SK_ID_C_SPT_REV:
125		case SK_ID_DC_SPT:
126		case SK_ID_DC_SPT_REM:
127		case SK_ID_DEQ_X:
128		case SK_ID_DEQ_Y:
129		case SK_FIRST_CTN_PRE:
130		case SK_PREFIX:
131		case SK_SUFFIX_REM:
132		Unhandled() << "Expected to eliminate Skolem ID " << id << std::endl;
133		break;
134	114	case SK_NUM_OCCUR:
135		case SK_OCCUR_INDEX:
136		default:
137		{
138	114	Notice() << "Don't know how to handle Skolem ID " << id << std::endl;
139	228	Node v = nm->mkBoundVar(tn);
140	228	Node cond = nm->mkConst(true);
141	228	sk = sm->mkSkolem(v, cond, c, "string skolem");
142		}
143	114	break;
144		}
145	11010	Trace("skolem-cache") << "...returned " << sk << std::endl;
146	11010	d_allSkolems.insert(sk);
147	11010	d_skolemCache[a][b][id] = sk;
148	11010	return sk;
149		}
150	187	Node SkolemCache::mkTypedSkolemCached(TypeNode tn,
151		Node a,
152		SkolemId id,
153		const char* c)
154		{
155	187	return mkTypedSkolemCached(tn, a, Node::null(), id, c);
156		}
157
158	19	Node SkolemCache::mkSkolemSeqNth(TypeNode seqType, const char* c)
159		{
160		// Note this method is static and does not rely on any local caching.
161		// It is used by expand definitions and by (dynamic) reductions, thus
162		// it is centrally located here.
163	19	Assert(seqType.isSequence());
164	19	NodeManager* nm = NodeManager::currentNM();
165	19	SkolemManager* sm = nm->getSkolemManager();
166	38	std::vector<TypeNode> argTypes;
167	19	argTypes.push_back(seqType);
168	19	argTypes.push_back(nm->integerType());
169	38	TypeNode elemType = seqType.getSequenceElementType();
170	38	TypeNode ufType = nm->mkFunctionType(argTypes, elemType);
171	38	return sm->mkSkolemFunction(SkolemFunId::SEQ_NTH_OOB, ufType);
172		}
173
174	1125	Node SkolemCache::mkSkolem(const char* c)
175		{
176		// TODO: eliminate this
177	1125	SkolemManager* sm = NodeManager::currentNM()->getSkolemManager();
178	1125	Node n = sm->mkDummySkolem(c, d_strType, "string skolem");
179	1125	d_allSkolems.insert(n);
180	1125	return n;
181		}
182
183	4234	bool SkolemCache::isSkolem(Node n) const
184		{
185	4234	return d_allSkolems.find(n) != d_allSkolems.end();
186		}
187
188		std::tuple<SkolemCache::SkolemId, Node, Node>
189	25225	SkolemCache::normalizeStringSkolem(SkolemId id, Node a, Node b)
190		{
191
192	25225	NodeManager* nm = NodeManager::currentNM();
193
194		// eliminate in terms of prefix/suffix_rem
195	25225	if (id == SK_FIRST_CTN_POST)
196		{
197		// SK_FIRST_CTN_POST(x, y) --->
198		// SK_SUFFIX_REM(x, (+ (str.len SK_FIRST_CTN_PRE(x, y)) (str.len y)))
199	2249	id = SK_SUFFIX_REM;
200	4498	Node pre = mkSkolemCached(a, b, SK_FIRST_CTN_PRE, "pre");
201	6747	b = nm->mkNode(
202	8996	PLUS, nm->mkNode(STRING_LENGTH, pre), nm->mkNode(STRING_LENGTH, b));
203		}
204	22976	else if (id == SK_ID_V_SPT \|\| id == SK_ID_C_SPT)
205		{
206		// SK_ID_*_SPT(x, y) ---> SK_SUFFIX_REM(x, (str.len y))
207	461	id = SK_SUFFIX_REM;
208	461	b = nm->mkNode(STRING_LENGTH, b);
209		}
210	22515	else if (id == SK_ID_V_SPT_REV \|\| id == SK_ID_C_SPT_REV)
211		{
212		// SK_ID_*_SPT_REV(x, y) ---> SK_PREFIX(x, (- (str.len x) (str.len y)))
213	435	id = SK_PREFIX;
214	1740	b = nm->mkNode(
215	1740	MINUS, nm->mkNode(STRING_LENGTH, a), nm->mkNode(STRING_LENGTH, b));
216		}
217	22080	else if (id == SK_ID_VC_SPT)
218		{
219		// SK_ID_VC_SPT(x, y) ---> SK_SUFFIX_REM(x, 1)
220	1996	id = SK_SUFFIX_REM;
221	1996	b = nm->mkConst(Rational(1));
222		}
223	20084	else if (id == SK_ID_VC_SPT_REV)
224		{
225		// SK_ID_VC_SPT_REV(x, y) ---> SK_PREFIX(x, (- (str.len x) 1))
226	2076	id = SK_PREFIX;
227	6228	b = nm->mkNode(
228	8304	MINUS, nm->mkNode(STRING_LENGTH, a), nm->mkConst(Rational(1)));
229		}
230	18008	else if (id == SK_ID_DC_SPT)
231		{
232		// SK_ID_DC_SPT(x, y) ---> SK_PREFIX(x, 1)
233		id = SK_PREFIX;
234		b = nm->mkConst(Rational(1));
235		}
236	18008	else if (id == SK_ID_DC_SPT_REM)
237		{
238		// SK_ID_DC_SPT_REM(x, y) ---> SK_SUFFIX_REM(x, 1)
239		id = SK_SUFFIX_REM;
240		b = nm->mkConst(Rational(1));
241		}
242	18008	else if (id == SK_ID_DEQ_X)
243		{
244		// SK_ID_DEQ_X(x, y) ---> SK_PREFIX(y, (str.len x))
245		id = SK_PREFIX;
246		Node aOld = a;
247		a = b;
248		b = nm->mkNode(STRING_LENGTH, aOld);
249		}
250	18008	else if (id == SK_ID_DEQ_Y)
251		{
252		// SK_ID_DEQ_Y(x, y) ---> SK_PREFIX(x, (str.len y))
253		id = SK_PREFIX;
254		b = nm->mkNode(STRING_LENGTH, b);
255		}
256	18008	else if (id == SK_FIRST_CTN_PRE)
257		{
258		// SK_FIRST_CTN_PRE(x,y) ---> SK_PREFIX(x, indexof(x,y,0))
259	4502	id = SK_PREFIX;
260	4502	b = nm->mkNode(STRING_INDEXOF, a, b, d_zero);
261		}
262
263	25225	if (id == SK_ID_V_UNIFIED_SPT \|\| id == SK_ID_V_UNIFIED_SPT_REV)
264		{
265	3621	bool isRev = (id == SK_ID_V_UNIFIED_SPT_REV);
266	7242	Node la = nm->mkNode(STRING_LENGTH, a);
267	7242	Node lb = nm->mkNode(STRING_LENGTH, b);
268	5135	Node ta = isRev ? utils::mkPrefix(a, nm->mkNode(MINUS, la, lb))
269	8756	: utils::mkSuffix(a, lb);
270	5135	Node tb = isRev ? utils::mkPrefix(b, nm->mkNode(MINUS, lb, la))
271	8756	: utils::mkSuffix(b, la);
272	3621	id = SK_PURIFY;
273		// SK_ID_V_UNIFIED_SPT(x,y) --->
274		// ite(len(x) >= len(y), substr(x,0,str.len(y)), substr(y,0,str.len(x))
275	3621	a = nm->mkNode(ITE, nm->mkNode(GEQ, la, lb), ta, tb);
276	3621	b = Node::null();
277		}
278
279		// now, eliminate prefix/suffix_rem in terms of purify
280	25225	if (id == SK_PREFIX)
281		{
282		// SK_PREFIX(x,y) ---> SK_PURIFY(substr(x,0,y))
283	8077	id = SK_PURIFY;
284	8077	a = utils::mkPrefix(a, b);
285	8077	b = Node::null();
286		}
287	17148	else if (id == SK_SUFFIX_REM)
288		{
289		// SK_SUFFIX_REM(x,y) ---> SK_PURIFY(substr(x,y,str.len(x)-y))
290	5770	id = SK_PURIFY;
291	5770	a = utils::mkSuffix(a, b);
292	5770	b = Node::null();
293		}
294
295	25225	if (d_useOpts)
296		{
297	25052	a = a.isNull() ? a : Rewriter::rewrite(a);
298	25052	b = b.isNull() ? b : Rewriter::rewrite(b);
299		}
300	50450	Trace("skolem-cache") << "normalizeStringSkolem end: (" << id << ", " << a
301	25225	<< ", " << b << ")" << std::endl;
302	25225	return std::make_tuple(id, a, b);
303		}
304
305	283	Node SkolemCache::mkIndexVar(Node t)
306		{
307	283	NodeManager* nm = NodeManager::currentNM();
308	566	TypeNode intType = nm->integerType();
309	283	BoundVarManager* bvm = nm->getBoundVarManager();
310	566	return bvm->mkBoundVar<IndexVarAttribute>(t, intType);
311		}
312
313	78	Node SkolemCache::mkLengthVar(Node t)
314		{
315	78	NodeManager* nm = NodeManager::currentNM();
316	156	TypeNode intType = nm->integerType();
317	78	BoundVarManager* bvm = nm->getBoundVarManager();
318	156	return bvm->mkBoundVar<LengthVarAttribute>(t, intType);
319		}
320
321		} // namespace strings
322		} // namespace theory
323	22746	} // namespace cvc5