Head

GCC Code Coverage Report

Directory:	.		Exec	Total	Coverage
File:	src/theory/strings/strings_rewriter.cpp	Lines:	161	161	100.0 %
Date:	2021-05-22	Branches:	422	876	48.2 %


/******************************************************************************
 * Top contributors (to current version):
 *   Andrew Reynolds, Andres Noetzli, Gereon Kremer
 *
 * 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 rewrite rules for string-specific operators in
 * theory of strings.
 */

#include "theory/strings/strings_rewriter.h"

#include "expr/node_builder.h"
#include "theory/strings/theory_strings_utils.h"
#include "util/rational.h"

using namespace cvc5::kind;

namespace cvc5 {
namespace theory {
namespace strings {

StringsRewriter::StringsRewriter(HistogramStat<Rewrite>* statistics)
    : SequencesRewriter(statistics)
{
}

RewriteResponse StringsRewriter::postRewrite(TNode node)
{
  Trace("strings-postrewrite")
      << "Strings::StringsRewriter::postRewrite start " << node << std::endl;

  Node retNode = node;
  Kind nk = node.getKind();
  if (nk == kind::STRING_LT)
  {
    retNode = rewriteStringLt(node);
  }
  else if (nk == kind::STRING_LEQ)
  {
    retNode = rewriteStringLeq(node);
  }
  else if (nk == STRING_TOLOWER || nk == STRING_TOUPPER)
  {
    retNode = rewriteStrConvert(node);
  }
  else if (nk == STRING_IS_DIGIT)
  {
    retNode = rewriteStringIsDigit(node);
  }
  else if (nk == kind::STRING_ITOS)
  {
    retNode = rewriteIntToStr(node);
  }
  else if (nk == kind::STRING_STOI)
  {
    retNode = rewriteStrToInt(node);
  }
  else if (nk == STRING_TO_CODE)
  {
    retNode = rewriteStringToCode(node);
  }
  else if (nk == STRING_FROM_CODE)
  {
    retNode = rewriteStringFromCode(node);
  }
  else
  {
    return SequencesRewriter::postRewrite(node);
  }

  Trace("strings-postrewrite")
      << "Strings::StringsRewriter::postRewrite returning " << retNode
      << std::endl;
  if (node != retNode)
  {
    Trace("strings-rewrite-debug") << "Strings::StringsRewriter::postRewrite "
                                   << node << " to " << retNode << std::endl;
    return RewriteResponse(REWRITE_AGAIN_FULL, retNode);
  }
  return RewriteResponse(REWRITE_DONE, retNode);
}

Node StringsRewriter::rewriteStrToInt(Node node)
{
  Assert(node.getKind() == STRING_STOI);
  NodeManager* nm = NodeManager::currentNM();
  if (node[0].isConst())
  {
    Node ret;
    String s = node[0].getConst<String>();
    if (s.isNumber())
    {
      ret = nm->mkConst(s.toNumber());
    }
    else
    {
      ret = nm->mkConst(Rational(-1));
    }
    return returnRewrite(node, ret, Rewrite::STOI_EVAL);
  }
  else if (node[0].getKind() == STRING_CONCAT)
  {
    for (TNode nc : node[0])
    {
      if (nc.isConst())
      {
        String t = nc.getConst<String>();
        if (!t.isNumber())
        {
          Node ret = nm->mkConst(Rational(-1));
          return returnRewrite(node, ret, Rewrite::STOI_CONCAT_NONNUM);
        }
      }
    }
  }
  return node;
}

Node StringsRewriter::rewriteIntToStr(Node node)
{
  Assert(node.getKind() == STRING_ITOS);
  NodeManager* nm = NodeManager::currentNM();
  if (node[0].isConst())
  {
    Node ret;
    if (node[0].getConst<Rational>().sgn() == -1)
    {
      ret = nm->mkConst(String(""));
    }
    else
    {
      std::string stmp = node[0].getConst<Rational>().getNumerator().toString();
      Assert(stmp[0] != '-');
      ret = nm->mkConst(String(stmp));
    }
    return returnRewrite(node, ret, Rewrite::ITOS_EVAL);
  }
  return node;
}

Node StringsRewriter::rewriteStrConvert(Node node)
{
  Kind nk = node.getKind();
  Assert(nk == STRING_TOLOWER || nk == STRING_TOUPPER);
  NodeManager* nm = NodeManager::currentNM();
  if (node[0].isConst())
  {
    std::vector<unsigned> nvec = node[0].getConst<String>().getVec();
    for (unsigned i = 0, nvsize = nvec.size(); i < nvsize; i++)
    {
      unsigned newChar = nvec[i];
      // transform it
      // upper 65 ... 90
      // lower 97 ... 122
      if (nk == STRING_TOUPPER)
      {
        if (newChar >= 97 && newChar <= 122)
        {
          newChar = newChar - 32;
        }
      }
      else if (nk == STRING_TOLOWER)
      {
        if (newChar >= 65 && newChar <= 90)
        {
          newChar = newChar + 32;
        }
      }
      nvec[i] = newChar;
    }
    Node retNode = nm->mkConst(String(nvec));
    return returnRewrite(node, retNode, Rewrite::STR_CONV_CONST);
  }
  else if (node[0].getKind() == STRING_CONCAT)
  {
    NodeBuilder concatBuilder(STRING_CONCAT);
    for (const Node& nc : node[0])
    {
      concatBuilder << nm->mkNode(nk, nc);
    }
    // tolower( x1 ++ x2 ) --> tolower( x1 ) ++ tolower( x2 )
    Node retNode = concatBuilder.constructNode();
    return returnRewrite(node, retNode, Rewrite::STR_CONV_MINSCOPE_CONCAT);
  }
  else if (node[0].getKind() == STRING_TOLOWER
           || node[0].getKind() == STRING_TOUPPER)
  {
    // tolower( tolower( x ) ) --> tolower( x )
    // tolower( toupper( x ) ) --> tolower( x )
    Node retNode = nm->mkNode(nk, node[0][0]);
    return returnRewrite(node, retNode, Rewrite::STR_CONV_IDEM);
  }
  else if (node[0].getKind() == STRING_ITOS)
  {
    // tolower( str.from.int( x ) ) --> str.from.int( x )
    return returnRewrite(node, node[0], Rewrite::STR_CONV_ITOS);
  }
  return node;
}

Node StringsRewriter::rewriteStringLt(Node n)
{
  Assert(n.getKind() == kind::STRING_LT);
  NodeManager* nm = NodeManager::currentNM();
  // eliminate s < t ---> s != t AND s <= t
  Node retNode = nm->mkNode(
      AND, n[0].eqNode(n[1]).negate(), nm->mkNode(STRING_LEQ, n[0], n[1]));
  return returnRewrite(n, retNode, Rewrite::STR_LT_ELIM);
}

Node StringsRewriter::rewriteStringLeq(Node n)
{
  Assert(n.getKind() == kind::STRING_LEQ);
  NodeManager* nm = NodeManager::currentNM();
  if (n[0] == n[1])
  {
    Node ret = nm->mkConst(true);
    return returnRewrite(n, ret, Rewrite::STR_LEQ_ID);
  }
  if (n[0].isConst() && n[1].isConst())
  {
    String s = n[0].getConst<String>();
    String t = n[1].getConst<String>();
    Node ret = nm->mkConst(s.isLeq(t));
    return returnRewrite(n, ret, Rewrite::STR_LEQ_EVAL);
  }
  // empty strings
  for (unsigned i = 0; i < 2; i++)
  {
    if (n[i].isConst() && n[i].getConst<String>().empty())
    {
      Node ret = i == 0 ? nm->mkConst(true) : n[0].eqNode(n[1]);
      return returnRewrite(n, ret, Rewrite::STR_LEQ_EMPTY);
    }
  }

  std::vector<Node> n1;
  utils::getConcat(n[0], n1);
  std::vector<Node> n2;
  utils::getConcat(n[1], n2);
  Assert(!n1.empty() && !n2.empty());

  // constant prefixes
  if (n1[0].isConst() && n2[0].isConst() && n1[0] != n2[0])
  {
    String s = n1[0].getConst<String>();
    String t = n2[0].getConst<String>();
    size_t prefixLen = std::min(s.size(), t.size());
    s = s.prefix(prefixLen);
    t = t.prefix(prefixLen);
    // if the prefixes are not the same, then we can already decide the outcome
    if (s != t)
    {
      Node ret = nm->mkConst(s.isLeq(t));
      return returnRewrite(n, ret, Rewrite::STR_LEQ_CPREFIX);
    }
  }
  return n;
}

Node StringsRewriter::rewriteStringFromCode(Node n)
{
  Assert(n.getKind() == kind::STRING_FROM_CODE);
  NodeManager* nm = NodeManager::currentNM();

  if (n[0].isConst())
  {
    Integer i = n[0].getConst<Rational>().getNumerator();
    Node ret;
    if (i >= 0 && i < strings::utils::getAlphabetCardinality())
    {
      std::vector<unsigned> svec = {i.toUnsignedInt()};
      ret = nm->mkConst(String(svec));
    }
    else
    {
      ret = nm->mkConst(String(""));
    }
    return returnRewrite(n, ret, Rewrite::FROM_CODE_EVAL);
  }
  return n;
}

Node StringsRewriter::rewriteStringToCode(Node n)
{
  Assert(n.getKind() == kind::STRING_TO_CODE);
  if (n[0].isConst())
  {
    NodeManager* nm = NodeManager::currentNM();
    String s = n[0].getConst<String>();
    Node ret;
    if (s.size() == 1)
    {
      std::vector<unsigned> vec = s.getVec();
      Assert(vec.size() == 1);
      ret = nm->mkConst(Rational(vec[0]));
    }
    else
    {
      ret = nm->mkConst(Rational(-1));
    }
    return returnRewrite(n, ret, Rewrite::TO_CODE_EVAL);
  }
  return n;
}

Node StringsRewriter::rewriteStringIsDigit(Node n)
{
  Assert(n.getKind() == kind::STRING_IS_DIGIT);
  NodeManager* nm = NodeManager::currentNM();
  // eliminate str.is_digit(s) ----> 48 <= str.to_code(s) <= 57
  Node t = nm->mkNode(STRING_TO_CODE, n[0]);
  Node retNode = nm->mkNode(AND,
                            nm->mkNode(LEQ, nm->mkConst(Rational(48)), t),
                            nm->mkNode(LEQ, t, nm->mkConst(Rational(57))));
  return returnRewrite(n, retNode, Rewrite::IS_DIGIT_ELIM);
}

}  // 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, Gereon Kremer
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 rewrite rules for string-specific operators in
14		* theory of strings.
15		*/
16
17		#include "theory/strings/strings_rewriter.h"
18
19		#include "expr/node_builder.h"
20		#include "theory/strings/theory_strings_utils.h"
21		#include "util/rational.h"
22
23		using namespace cvc5::kind;
24
25		namespace cvc5 {
26		namespace theory {
27		namespace strings {
28
29	9472	StringsRewriter::StringsRewriter(HistogramStat<Rewrite>* statistics)
30	9472	: SequencesRewriter(statistics)
31		{
32	9472	}
33
34	400486	RewriteResponse StringsRewriter::postRewrite(TNode node)
35		{
36	800972	Trace("strings-postrewrite")
37	400486	<< "Strings::StringsRewriter::postRewrite start " << node << std::endl;
38
39	800972	Node retNode = node;
40	400486	Kind nk = node.getKind();
41	400486	if (nk == kind::STRING_LT)
42		{
43	17	retNode = rewriteStringLt(node);
44		}
45	400469	else if (nk == kind::STRING_LEQ)
46		{
47	343	retNode = rewriteStringLeq(node);
48		}
49	400126	else if (nk == STRING_TOLOWER \|\| nk == STRING_TOUPPER)
50		{
51	216	retNode = rewriteStrConvert(node);
52		}
53	399910	else if (nk == STRING_IS_DIGIT)
54		{
55	8	retNode = rewriteStringIsDigit(node);
56		}
57	399902	else if (nk == kind::STRING_ITOS)
58		{
59	559	retNode = rewriteIntToStr(node);
60		}
61	399343	else if (nk == kind::STRING_STOI)
62		{
63	471	retNode = rewriteStrToInt(node);
64		}
65	398872	else if (nk == STRING_TO_CODE)
66		{
67	3712	retNode = rewriteStringToCode(node);
68		}
69	395160	else if (nk == STRING_FROM_CODE)
70		{
71	84	retNode = rewriteStringFromCode(node);
72		}
73		else
74		{
75	395076	return SequencesRewriter::postRewrite(node);
76		}
77
78	10820	Trace("strings-postrewrite")
79	5410	<< "Strings::StringsRewriter::postRewrite returning " << retNode
80	5410	<< std::endl;
81	5410	if (node != retNode)
82		{
83	3236	Trace("strings-rewrite-debug") << "Strings::StringsRewriter::postRewrite "
84	1618	<< node << " to " << retNode << std::endl;
85	1618	return RewriteResponse(REWRITE_AGAIN_FULL, retNode);
86		}
87	3792	return RewriteResponse(REWRITE_DONE, retNode);
88		}
89
90	471	Node StringsRewriter::rewriteStrToInt(Node node)
91		{
92	471	Assert(node.getKind() == STRING_STOI);
93	471	NodeManager* nm = NodeManager::currentNM();
94	471	if (node[0].isConst())
95		{
96	382	Node ret;
97	382	String s = node[0].getConst<String>();
98	191	if (s.isNumber())
99		{
100	91	ret = nm->mkConst(s.toNumber());
101		}
102		else
103		{
104	100	ret = nm->mkConst(Rational(-1));
105		}
106	191	return returnRewrite(node, ret, Rewrite::STOI_EVAL);
107		}
108	280	else if (node[0].getKind() == STRING_CONCAT)
109		{
110	752	for (TNode nc : node[0])
111		{
112	624	if (nc.isConst())
113		{
114	36	String t = nc.getConst<String>();
115	20	if (!t.isNumber())
116		{
117	8	Node ret = nm->mkConst(Rational(-1));
118	4	return returnRewrite(node, ret, Rewrite::STOI_CONCAT_NONNUM);
119		}
120		}
121		}
122		}
123	276	return node;
124		}
125
126	559	Node StringsRewriter::rewriteIntToStr(Node node)
127		{
128	559	Assert(node.getKind() == STRING_ITOS);
129	559	NodeManager* nm = NodeManager::currentNM();
130	559	if (node[0].isConst())
131		{
132	526	Node ret;
133	263	if (node[0].getConst<Rational>().sgn() == -1)
134		{
135	129	ret = nm->mkConst(String(""));
136		}
137		else
138		{
139	268	std::string stmp = node[0].getConst<Rational>().getNumerator().toString();
140	134	Assert(stmp[0] != '-');
141	134	ret = nm->mkConst(String(stmp));
142		}
143	263	return returnRewrite(node, ret, Rewrite::ITOS_EVAL);
144		}
145	296	return node;
146		}
147
148	216	Node StringsRewriter::rewriteStrConvert(Node node)
149		{
150	216	Kind nk = node.getKind();
151	216	Assert(nk == STRING_TOLOWER \|\| nk == STRING_TOUPPER);
152	216	NodeManager* nm = NodeManager::currentNM();
153	216	if (node[0].isConst())
154		{
155	44	std::vector<unsigned> nvec = node[0].getConst<String>().getVec();
156	74	for (unsigned i = 0, nvsize = nvec.size(); i < nvsize; i++)
157		{
158	52	unsigned newChar = nvec[i];
159		// transform it
160		// upper 65 ... 90
161		// lower 97 ... 122
162	52	if (nk == STRING_TOUPPER)
163		{
164	18	if (newChar >= 97 && newChar <= 122)
165		{
166	16	newChar = newChar - 32;
167		}
168		}
169	34	else if (nk == STRING_TOLOWER)
170		{
171	34	if (newChar >= 65 && newChar <= 90)
172		{
173	25	newChar = newChar + 32;
174		}
175		}
176	52	nvec[i] = newChar;
177		}
178	44	Node retNode = nm->mkConst(String(nvec));
179	22	return returnRewrite(node, retNode, Rewrite::STR_CONV_CONST);
180		}
181	194	else if (node[0].getKind() == STRING_CONCAT)
182		{
183	108	NodeBuilder concatBuilder(STRING_CONCAT);
184	236	for (const Node& nc : node[0])
185		{
186	182	concatBuilder << nm->mkNode(nk, nc);
187		}
188		// tolower( x1 ++ x2 ) --> tolower( x1 ) ++ tolower( x2 )
189	108	Node retNode = concatBuilder.constructNode();
190	54	return returnRewrite(node, retNode, Rewrite::STR_CONV_MINSCOPE_CONCAT);
191		}
192	420	else if (node[0].getKind() == STRING_TOLOWER
193	420	\|\| node[0].getKind() == STRING_TOUPPER)
194		{
195		// tolower( tolower( x ) ) --> tolower( x )
196		// tolower( toupper( x ) ) --> tolower( x )
197	16	Node retNode = nm->mkNode(nk, node[0][0]);
198	8	return returnRewrite(node, retNode, Rewrite::STR_CONV_IDEM);
199		}
200	132	else if (node[0].getKind() == STRING_ITOS)
201		{
202		// tolower( str.from.int( x ) ) --> str.from.int( x )
203	4	return returnRewrite(node, node[0], Rewrite::STR_CONV_ITOS);
204		}
205	128	return node;
206		}
207
208	17	Node StringsRewriter::rewriteStringLt(Node n)
209		{
210	17	Assert(n.getKind() == kind::STRING_LT);
211	17	NodeManager* nm = NodeManager::currentNM();
212		// eliminate s < t ---> s != t AND s <= t
213		Node retNode = nm->mkNode(
214	34	AND, n[0].eqNode(n[1]).negate(), nm->mkNode(STRING_LEQ, n[0], n[1]));
215	34	return returnRewrite(n, retNode, Rewrite::STR_LT_ELIM);
216		}
217
218	343	Node StringsRewriter::rewriteStringLeq(Node n)
219		{
220	343	Assert(n.getKind() == kind::STRING_LEQ);
221	343	NodeManager* nm = NodeManager::currentNM();
222	343	if (n[0] == n[1])
223		{
224	42	Node ret = nm->mkConst(true);
225	21	return returnRewrite(n, ret, Rewrite::STR_LEQ_ID);
226		}
227	322	if (n[0].isConst() && n[1].isConst())
228		{
229	66	String s = n[0].getConst<String>();
230	66	String t = n[1].getConst<String>();
231	66	Node ret = nm->mkConst(s.isLeq(t));
232	33	return returnRewrite(n, ret, Rewrite::STR_LEQ_EVAL);
233		}
234		// empty strings
235	849	for (unsigned i = 0; i < 2; i++)
236		{
237	573	if (n[i].isConst() && n[i].getConst<String>().empty())
238		{
239	26	Node ret = i == 0 ? nm->mkConst(true) : n[0].eqNode(n[1]);
240	13	return returnRewrite(n, ret, Rewrite::STR_LEQ_EMPTY);
241		}
242		}
243
244	552	std::vector<Node> n1;
245	276	utils::getConcat(n[0], n1);
246	552	std::vector<Node> n2;
247	276	utils::getConcat(n[1], n2);
248	276	Assert(!n1.empty() && !n2.empty());
249
250		// constant prefixes
251	276	if (n1[0].isConst() && n2[0].isConst() && n1[0] != n2[0])
252		{
253	136	String s = n1[0].getConst<String>();
254	136	String t = n2[0].getConst<String>();
255	92	size_t prefixLen = std::min(s.size(), t.size());
256	92	s = s.prefix(prefixLen);
257	92	t = t.prefix(prefixLen);
258		// if the prefixes are not the same, then we can already decide the outcome
259	92	if (s != t)
260		{
261	96	Node ret = nm->mkConst(s.isLeq(t));
262	48	return returnRewrite(n, ret, Rewrite::STR_LEQ_CPREFIX);
263		}
264		}
265	228	return n;
266		}
267
268	84	Node StringsRewriter::rewriteStringFromCode(Node n)
269		{
270	84	Assert(n.getKind() == kind::STRING_FROM_CODE);
271	84	NodeManager* nm = NodeManager::currentNM();
272
273	84	if (n[0].isConst())
274		{
275	44	Integer i = n[0].getConst<Rational>().getNumerator();
276	44	Node ret;
277	22	if (i >= 0 && i < strings::utils::getAlphabetCardinality())
278		{
279	18	std::vector<unsigned> svec = {i.toUnsignedInt()};
280	9	ret = nm->mkConst(String(svec));
281		}
282		else
283		{
284	13	ret = nm->mkConst(String(""));
285		}
286	22	return returnRewrite(n, ret, Rewrite::FROM_CODE_EVAL);
287		}
288	62	return n;
289		}
290
291	3712	Node StringsRewriter::rewriteStringToCode(Node n)
292		{
293	3712	Assert(n.getKind() == kind::STRING_TO_CODE);
294	3712	if (n[0].isConst())
295		{
296	910	NodeManager* nm = NodeManager::currentNM();
297	1820	String s = n[0].getConst<String>();
298	1820	Node ret;
299	910	if (s.size() == 1)
300		{
301	924	std::vector<unsigned> vec = s.getVec();
302	462	Assert(vec.size() == 1);
303	462	ret = nm->mkConst(Rational(vec[0]));
304		}
305		else
306		{
307	448	ret = nm->mkConst(Rational(-1));
308		}
309	910	return returnRewrite(n, ret, Rewrite::TO_CODE_EVAL);
310		}
311	2802	return n;
312		}
313
314	8	Node StringsRewriter::rewriteStringIsDigit(Node n)
315		{
316	8	Assert(n.getKind() == kind::STRING_IS_DIGIT);
317	8	NodeManager* nm = NodeManager::currentNM();
318		// eliminate str.is_digit(s) ----> 48 <= str.to_code(s) <= 57
319	16	Node t = nm->mkNode(STRING_TO_CODE, n[0]);
320		Node retNode = nm->mkNode(AND,
321	16	nm->mkNode(LEQ, nm->mkConst(Rational(48)), t),
322	32	nm->mkNode(LEQ, t, nm->mkConst(Rational(57))));
323	16	return returnRewrite(n, retNode, Rewrite::IS_DIGIT_ELIM);
324		}
325
326		} // namespace strings
327		} // namespace theory
328	28194	} // namespace cvc5