theory_datatype2.cpp

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/*****************************************************************************/
/*!
 *\file theory_datatype.cpp
 *
 * Author: Clark Barrett
 *
 * Created: Wed Dec  1 22:32:26 2004
 *
 * <hr>
 * Copyright (C) 2003 by the Board of Trustees of Leland Stanford
 * Junior University and by New York University. 
 *
 * License to use, copy, modify, sell and/or distribute this software
 * and its documentation for any purpose is hereby granted without
 * royalty, subject to the terms and conditions defined in the \ref
 * LICENSE file provided with this distribution.  In particular:
 *
 * - The above copyright notice and this permission notice must appear
 * in all copies of the software and related documentation.
 *
 * - THE SOFTWARE IS PROVIDED "AS-IS", WITHOUT ANY WARRANTIES,
 * EXPRESSED OR IMPLIED.  USE IT AT YOUR OWN RISK.
 * 
 * <hr>
 * 
 */
/*****************************************************************************/


#include "theory_datatype.h"
#include "datatype_proof_rules.h"
#include "typecheck_exception.h"
#include "parser_exception.h"
#include "smtlib_exception.h"
#include "theory_core.h"


using namespace std;
using namespace CVCL;


///////////////////////////////////////////////////////////////////////////////
// TheoryDatatype Public Methods                                             //
///////////////////////////////////////////////////////////////////////////////


TheoryDatatype::TheoryDatatype(TheoryCore* core)
  : Theory(core, "Datatypes"),
    d_facts(core->getCM()->getCurrentContext())
{
  d_rules = createProofRules();

  // Register new local kinds with ExprManager
  getEM()->newKind(DATATYPE, "DATATYPE", true);
  getEM()->newKind(CONSTRUCTOR, "CONSTRUCTOR");
  getEM()->newKind(SELECTOR, "SELECTOR");
  getEM()->newKind(TESTER, "TESTER");

  vector<int> kinds;
  kinds.push_back(DATATYPE);
  kinds.push_back(TESTER);
  kinds.push_back(CONSTRUCTOR);
  kinds.push_back(SELECTOR);

  registerTheory(this, kinds);
}


TheoryDatatype::~TheoryDatatype() {
  delete d_rules;
}


void TheoryDatatype::instantiate(const Expr& e, const bigunsigned& u)
{
  DebugAssert(e.hasFind() && findExpr(e) == e,
              "datatype: instantiate: Expected find(e)=e");
  if (isConstructor(e)) return;
  DebugAssert(u != 0 && (u & (u-1)) == 0,
              "datatype: instantiate: Expected single label in u");
  DebugAssert(d_datatypes.find(e.getType().getExpr()) != d_datatypes.end(),
              "datatype: instantiate: Unexpected type: "+e.getType().toString()
              +"\n\n for expression: "+e.toString());
  ExprMap<unsigned>& c = d_datatypes[e.getType().getExpr()];
  ExprMap<unsigned>::iterator c_it = c.begin(), c_end = c.end();
  for (; c_it != c_end; ++c_it) {
    if (u & (1 << bigunsigned((*c_it).second))) break;
  }
  DebugAssert(c_it != c_end,
              "datatype: instantiate: couldn't find constructor");
  Expr cons = (*c_it).first;

  Type consType = cons.getType();
  if (consType.arity() == 1) {
    enqueueFact(d_rules->dummyTheorem(d_facts, e.eqExpr(cons)));
    return;
  }
  // create vars
  vector<Expr> vars;
  for (int i = 0; i < consType.arity()-1; ++i) {
    vars.push_back(getEM()->newBoundVarExpr(consType[i]));
  }
  Expr e2 = getEM()->newClosureExpr(EXISTS, vars,
                                    e.eqExpr(Expr(cons.mkOp(), vars)));
  enqueueFact(d_rules->dummyTheorem(d_facts, e2));
}


void TheoryDatatype::initializeLabels(const Expr& e, const Type& t)
{
  DebugAssert(findExpr(e) == e,
              "datatype: initializeLabels: Expected find(e)=e");
  DebugAssert(d_datatypes.find(t.getExpr()) != d_datatypes.end(),
              "Unknown datatype: "+t.getExpr().toString());
  ExprMap<unsigned>& c = d_datatypes[t.getExpr()];
  DebugAssert(d_labels.find(e) == d_labels.end(),
              "datatype: initializeLabels: expected unlabeled expr");
  if (isConstructor(e)) {
    Expr cons = getConstructor(e);
    DebugAssert(c.find(cons) != c.end(),
                "datatype: initializeLabels: Couldn't find constructor "
                +cons.toString());
    bigunsigned position = c[cons];
    d_labels[e] =
      SmartCDO<bigunsigned>(theoryCore()->getCM()->getCurrentContext(),
                            1 << position, 0);
  }
  else {
    DebugAssert(c.size() > 0, "No constructors?");
    bigunsigned value = (1 << bigunsigned(c.size())) - 1;
    d_labels[e] =
      SmartCDO<bigunsigned>(theoryCore()->getCM()->getCurrentContext(),
                            value, 0);
    if (value == 1) instantiate(e, 1);
  }
}


void TheoryDatatype::mergeLabels(const Expr& e1, const Expr& e2)
{
  DebugAssert(e2.hasFind() && findExpr(e2) == e2,
              "datatype: mergeLabels: Expected find(e2)=e2");
  DebugAssert(d_labels.find(e1) != d_labels.end() &&
              d_labels.find(e2) != d_labels.end(),
              "mergeLabels: expr is not labeled");
  DebugAssert(e1.getType() == e2.getType(), "Expected same type");
  bigunsigned u = d_labels[e2].get();
  bigunsigned uNew = u & d_labels[e1].get();
  if (u != uNew) {
    d_labels[e2].set(uNew);
    if (uNew == 0)
      setInconsistent(d_rules->dummyTheorem(d_facts, falseExpr()));
    else if (((uNew - 1) & uNew) == 0) {
      instantiate(e2, uNew);
    }
  }
}


void TheoryDatatype::mergeLabels(const Expr& e, unsigned position, bool positive)
{
  DebugAssert(e.hasFind() && findExpr(e) == e,
              "datatype: mergeLabels2: Expected find(e)=e");
  DebugAssert(d_labels.find(e) != d_labels.end(),
              "mergeLabels2: expr is not labeled");
  bigunsigned u = d_labels[e].get();
  bigunsigned uNew = 1 << bigunsigned(position);
  if (positive) {
    uNew = u & uNew;
    if (u == uNew) return;
  } else if (u & uNew) uNew = u - uNew;
  else return;
  d_labels[e].set(uNew);
  if (uNew == 0)
    setInconsistent(d_rules->dummyTheorem(d_facts, falseExpr()));
  else if (((uNew - 1) & uNew) == 0) {
    instantiate(e, uNew);
  }
}


void TheoryDatatype::addSharedTerm(const Expr& e)
{
  if (e.getType().getExpr().getKind() == DATATYPE &&
      d_labels.find(e) == d_labels.end()) {
    initializeLabels(e, e.getType());
    e.addToNotify(this, Expr());
  }
}


void TheoryDatatype::assertFact(const Theorem& e)
{
  if (!e.isRewrite()) {
    const Expr& expr = e.getExpr();
    if (expr.getOpKind() == TESTER) {
      d_facts.push_back(e);
      mergeLabels(expr[0],
                  getConsPos(getConsForTester(expr.getOpExpr())),
                  true);
    }
    else if (expr.isNot() && expr[0].getOpKind() == TESTER) {
      d_facts.push_back(e);
      mergeLabels(expr[0][0],
                  getConsPos(getConsForTester(expr[0].getOpExpr())),
                  false);
    }
  }
}


void TheoryDatatype::checkSat(bool fullEffort)
{
}


Theorem TheoryDatatype::rewrite(const Expr& e)
{
  Theorem thm;
  if (isSelector(e)) {
    if (isConstructor(e[0])) {
      thm = d_rules->rewriteSelCons(e);
      return transitivityRule(thm, simplify(thm.getRHS()));
    }
  }
  else if (isTester(e)) {
    if (isConstructor(e[0])) {
      return d_rules->rewriteTestCons(e);
    }
  }
  return reflexivityRule(e);
}


void TheoryDatatype::setup(const Expr& e)
{
  if (e.getType().getExpr().getKind() == DATATYPE &&
      d_labels.find(e) == d_labels.end()) {
    initializeLabels(e, e.getType());
    e.addToNotify(this, Expr());
  }
  if (e.getKind() != APPLY) return;
  setupCC(e);
}


void TheoryDatatype::update(const Theorem& e, const Expr& d)
{
  if (d.isNull()) {
    d_facts.push_back(e);
    mergeLabels(e.getLHS(), e.getRHS());
  }
  else {
    const Theorem& dEQdsig = d.getSig();
    if (!dEQdsig.isNull()) {
      const Expr& dsig = dEQdsig.getRHS();
      Theorem thm = updateHelper(d);
      const Expr& sigNew = thm.getRHS();
      if (sigNew == dsig) return;
      dsig.setRep(Theorem());
      if (isSelector(sigNew) && isConstructor(sigNew[0])) {
        d.setSig(Theorem());
        enqueueFact(transitivityRule(thm, d_rules->rewriteSelCons(sigNew)));
      }
      else if (isTester(sigNew) && isConstructor(sigNew[0])) {
        d.setSig(Theorem());
        enqueueFact(transitivityRule(thm, d_rules->rewriteTestCons(sigNew)));
      }
      else {
        const Theorem& repEQsigNew = sigNew.getRep();
        if (!repEQsigNew.isNull()) {
          d.setSig(Theorem());
          enqueueFact(transitivityRule(repEQsigNew, symmetryRule(thm)));
        }
        else {
          int k, ar(d.arity());
          for (k = 0; k < ar; ++k) {
            if (sigNew[k] != dsig[k]) {
              sigNew[k].addToNotify(this, d);
            }
          }
          d.setSig(thm);
          sigNew.setRep(thm);
        }
      }
    }
  }
}


Theorem TheoryDatatype::solve(const Theorem& e)
{
  DebugAssert(e.isRewrite() && e.getLHS().isTerm(), "Expected equality");
  const Expr& lhs = e.getLHS();
  if (isConstructor(lhs) && !isConstructor(e.getRHS())) {
    return symmetryRule(e);
  }
  return e;
}


void TheoryDatatype::checkType(const Expr& e)
{
  switch (e.getKind()) {
    case DATATYPE: {
      if (e.arity() != 1 || !e[0].isString())
        throw Exception("Ill-formed datatype"+e.toString());
      if (resolveID(e[0].getString()) != e)
        throw Exception("Unknown datatype"+e.toString());
      break;
    }
    case CONSTRUCTOR:
    case SELECTOR:
    case TESTER:
      throw Exception("Non-type: "+e.toString());
    default:
      DebugAssert(false, "Unexpected kind in TheoryDatatype::checkType"
                  +getEM()->getKindName(e.getKind()));
  }
}


void TheoryDatatype::computeType(const Expr& e)
{
  switch (e.getOpKind()) {
    case CONSTRUCTOR:
    case SELECTOR:
    case TESTER: {
      DebugAssert(e.isApply(), "Expected application");
      Expr op = e.getOp().getExpr();
      Type t = op.lookupType();
      DebugAssert(!t.isNull(), "Expected operator to be well-typed");
      if (t.getExpr().getKind() == DATATYPE) {
        if (e.arity() != 0)
          throw TypecheckException("Expected no children: "+e.toString());
        e.setType(t);
        break;
      }
      else {
        DebugAssert(t.getExpr().getKind() == ARROW, "Expected function type");
        if (e.arity() != t.getExpr().arity()-1)
          throw TypecheckException("Wrong number of children:\n"+e.toString());
        Expr::iterator i = e.begin(), iend = e.end();
        Expr::iterator j = t.getExpr().begin();
        Expr arg;
        for (; i != iend; ++i, ++j) {
          arg = getBaseType(*i).getExpr();
          if (arg != getBaseType(*j)) {
            throw TypecheckException("Type mismatch for expression:\n\n  "
                                     + (*i).toString()
                                     + "\n\nhas the following type:\n\n  "
                                     + (*i).getType().getExpr().toString()
                                     + "\n\nbut the expected type is:\n\n  "
                                     + (*j).toString()
                                     + "\n\nin datatype function application:\n\n  "
                                     + e.toString());
          }
        }
        e.setType(*j);
      }
      break;
    }
    default:
      DebugAssert(false, "Unexpected kind in datatype::computeType: "
                  +e.toString());
  }
}


void TheoryDatatype::computeModelTerm(const Expr& e, std::vector<Expr>& v) {
}



Expr TheoryDatatype::computeTCC(const Expr& e)
{
  return trueExpr();
}

///////////////////////////////////////////////////////////////////////////////
// Pretty-printing                                                           //
///////////////////////////////////////////////////////////////////////////////


ExprStream& TheoryDatatype::print(ExprStream& os, const Expr& e) {
  switch (os.lang()) {
    case PRESENTATION_LANG:
      switch (e.getKind()) {
        case DATATYPE:
          if (e.arity() == 1 && e[0].isString()) {
            os << e[0].getString();
          }
          else e.printAST(os);
          break;
        case APPLY:
          os << e.getOpExpr();
          if(e.arity() > 0) {
            os << "(" << push;
            bool first(true);
            for (Expr::iterator i=e.begin(), iend=e.end(); i!=iend; ++i) {
              if(first) first = false;
              else os << "," << space;
              os << *i;
            }
            os << push << ")";
          }
          break;
        case CONSTRUCTOR:
        case SELECTOR:
        case TESTER:
          DebugAssert(e.isSymbol(), "Expected symbol");
          os << e.getName();
          break;
        default:
          DebugAssert(false, "TheoryDatatype::print: Unexpected kind: "
                      +getEM()->getKindName(e.getKind()));
      }
      break;
    case SMTLIB_LANG:
      FatalAssert(false, "Not Implemented Yet");
      break;
    case LISP_LANG:
      FatalAssert(false, "Not Implemented Yet");
      break;
    default:
      e.printAST(os);
      break;
  }
  return os;
}

//////////////////////////////////////////////////////////////////////////////
//parseExprOp:
//translating special Exprs to regular EXPR??
///////////////////////////////////////////////////////////////////////////////
Expr TheoryDatatype::parseExprOp(const Expr& e)
{
  // If the expression is not a list, it must have been already
  // parsed, so just return it as is.
  if(RAW_LIST != e.getKind()) return e;

  DebugAssert(e.arity() > 0,
              "TheoryDatatype::parseExprOp:\n e = "+e.toString());
  
  DebugAssert(e[0].getKind() == ID,
              "Expected ID kind for first elem in list expr");

  const Expr& c1 = e[0][0];
  int kind = getEM()->getKind(c1.getString());
  switch(kind) {
    case DATATYPE: {
      DebugAssert(e.arity() > 1,
                  "Empty DATATYPE expression\n"
                  " (expected at least one datatype): "+e.toString());

      vector<string> names;
      vector<vector<string> > allConstructorNames(e.arity()-1);
      vector<vector<vector<string> > > allSelectorNames(e.arity()-1);
      vector<vector<vector<Expr> > > allTypes(e.arity()-1);
      int i,j,k;
      Expr dt, constructor, selectors, selector;

      // Get names of datatypes
      ExprMap<bool> namesMap;
      for (i = 0; i < e.arity()-1; ++i) {
        dt = e[i+1];
        DebugAssert(dt.getKind() == RAW_LIST && dt.arity() == 2,
                    "Bad formed datatype expression"
                    +dt.toString());
        DebugAssert(dt[0].getKind() == ID,
                    "Expected ID kind for datatype name"
                    +dt.toString());
        names.push_back(dt[0][0].getString());
        if (namesMap.count(dt[0][0]) != 0) {
          throw ParserException("Datatype name used more than once"+names.back());
        }
        namesMap.insert(dt[0][0], true);
      }

      // Loop through datatypes
      for (i = 0; i < e.arity()-1; ++i) {
        dt = e[i+1];
        DebugAssert(dt[1].getKind() == RAW_LIST && dt[1].arity() > 0,
                    "Expected non-empty list for datatype constructors"
                    +dt.toString());
        dt = dt[1];
        vector<string>& constructorNames = allConstructorNames[i];
        vector<vector<string> >& selectorNames = allSelectorNames[i];
        selectorNames.resize(dt.arity());
        vector<vector<Expr> >& types = allTypes[i];
        types.resize(dt.arity());
        
        // Loop through constructors for this datatype
        for(j = 0; j < dt.arity(); ++j) {
          constructor = dt[j];
          DebugAssert(constructor.getKind() == RAW_LIST &&
                      (constructor.arity() == 1 || constructor.arity() == 2),
                    "Unexpected constructor"+constructor.toString());
          DebugAssert(constructor[0].getKind() == ID,
                      "Expected ID kind for constructor name"
                      +constructor.toString());
          constructorNames.push_back(constructor[0][0].getString());

          if (constructor.arity() == 2) {
            selectors = constructor[1];
            DebugAssert(selectors.getKind() == RAW_LIST && selectors.arity() > 0,
                        "Non-empty list expected as second argument of constructor:\n"
                        +constructor.toString());

            // Loop through selectors for this constructor
            for (k = 0; k < selectors.arity(); ++k) {
              selector = selectors[k];
              DebugAssert(selector.getKind() == RAW_LIST && selector.arity() == 2,
                          "Expected list of arity 2 for selector"
                          +selector.toString());
              DebugAssert(selector[0].getKind() == ID,
                          "Expected ID kind for selector name"
                          +selector.toString());
              selectorNames[j].push_back(selector[0][0].getString());
              DebugAssert(selector[1].getKind() == ID,
                          "Expected ID kind for selector type"
                          +selector.toString());
              if (namesMap.count(selector[1][0]) > 0) {
                types[j].push_back(selector[1][0]);
              }
              else {              
                types[j].push_back(parseExpr(selector[1]));
              }
            }
          }
        }
      }

      vector<Type> returnTypes;
      dataType(names, allConstructorNames, allSelectorNames, allTypes,
               returnTypes);
      return returnTypes[0].getExpr();
    }

    default: {
      throw ParserException("Unexpected datatype expression: "+e.toString());
    }
  }
  return e;
}


Type TheoryDatatype::dataType(const string& name,
                              const vector<string>& constructors,
                              const vector<vector<string> >& selectors,
                              const vector<vector<Expr> >& types)
{
  vector<string> names;
  vector<vector<string> > constructors2;
  vector<vector<vector<string> > > selectors2;
  vector<vector<vector<Expr> > > types2;
  vector<Type> returnTypes;
  names.push_back(name);
  constructors2.push_back(constructors);
  selectors2.push_back(selectors);
  types2.push_back(types);
  dataType(names, constructors2, selectors2, types2, returnTypes);
  return returnTypes[0];
}
 

// Elements of types are either the expr from an existing type or a string
// naming one of the datatypes being defined
void TheoryDatatype::dataType(const vector<string>& names,
                              const vector<vector<string> >& allConstructors,
                              const vector<vector<vector<string> > >& allSelectors,
                              const vector<vector<vector<Expr> > >& allTypes,
                              vector<Type>& returnTypes)
{
  //  bool wellFounded = false, infinite = false, 
  bool thisWellFounded;

  if (names.size() != allConstructors.size() ||
      allConstructors.size() != allSelectors.size() ||
      allSelectors.size() != allTypes.size()) {
    throw TypecheckException
      ("dataType: vector sizes don't match");
  }

  unsigned i, j, k;
  Expr e;

  for (i = 0; i < names.size(); ++i) {
    e = resolveID(names[i]);
    if (!e.isNull()) {
      throw TypecheckException
        ("Attempt to define datatype "+names[i]+":\n "
         "This variable is already defined.");
    }
    e = Expr(DATATYPE, getEM()->newStringExpr(names[i]));
    installID(names[i], e);
    returnTypes.push_back(Type(e));
  }

  for (i = 0; i < names.size(); ++i) {

    const vector<string>& constructors = allConstructors[i];
    const vector<vector<string> >& selectors = allSelectors[i];
    const vector<vector<Expr> >& types = allTypes[i];

    if (constructors.size() == 0) {
      throw TypecheckException
        ("datatype: "+names[i]+": must have at least one constructor");
    }
    if (constructors.size() != selectors.size() ||
        selectors.size() != types.size()) {
      throw TypecheckException
        ("dataType: vector sizes at index "+int2string(i)+" don't match");
    }

    ExprMap<unsigned>& constMap = d_datatypes[returnTypes[i].getExpr()];

    for (j = 0; j < constructors.size(); ++j) {
      Expr c = resolveID(constructors[j]);
      if (!c.isNull()) {
        throw TypecheckException
          ("Attempt to define datatype constructor "+constructors[j]+":\n "
           "This variable is already defined.");
      }
      c = getEM()->newSymbolExpr(constructors[j], CONSTRUCTOR);

      if (selectors[j].size() != types[j].size()) {
        throw TypecheckException
          ("dataType: constructor at index "+int2string(i)+", "+int2string(j)+
           ": number of selectors does not match number of types");
      }
      thisWellFounded = true;
      const vector<string>& sels = selectors[j];
      const vector<Expr>& tps = types[j];

      vector<Type> selTypes;
      Type t;
      Expr s;
      for (k = 0; k < sels.size(); ++k) {
        s = resolveID(sels[k]);
        if (!s.isNull()) {
          throw TypecheckException
            ("Attempt to define datatype selector "+sels[k]+":\n "
             "This variable is already defined.");
        }
        s = getEM()->newSymbolExpr(sels[k], SELECTOR);
        if (tps[k].isString()) {
          t = Type(resolveID(tps[k].getString()));
          if (t.isNull()) {
            throw TypecheckException
              ("Unable to resolve type identifier: "+tps[k].getString());
          }
        } else t = Type(tps[k]);
        if (t.isBool()) {
          throw TypecheckException
            ("Cannot have BOOLEAN inside of datatype");
        }
        else if (t.isFunction()) {
          throw TypecheckException
            ("Cannot have function inside of datatype");
        }
        
        selTypes.push_back(Type(t));
        s.setType(returnTypes[i].funType(Type(t)));
        if (isDatatype(Type(t)) && !t.getExpr().isWellFounded()) {
          thisWellFounded = false;
        }
        d_selectorMap[s] = pair<Expr,unsigned>(c,k);
        installID(sels[k], s);
      }
      if (thisWellFounded) c.setWellFounded();
      if (selTypes.size() == 0) c.setType(returnTypes[i]);
      else c.setType(Type::funType(selTypes, returnTypes[i]));
      installID(constructors[j], c);
      constMap[c] = j;

      string testerString = "is_"+constructors[j];
      e = resolveID(testerString);
      if (!e.isNull()) {
        throw TypecheckException
          ("Attempt to define datatype tester "+testerString+":\n "
           "This variable is already defined.");
      }
      e = getEM()->newSymbolExpr(testerString, TESTER);
      e.setType(returnTypes[i].funType(boolType()));
      d_testerMap[e] = c;
      installID(testerString, e);
    }
  }

  // Compute fixed point for wellfoundedness check

  bool changed;
  int firstNotWellFounded;
  do {
    changed = false;
    firstNotWellFounded = -1;
    for (i = 0; i < names.size(); ++i) {
      ExprMap<unsigned>& c = d_datatypes[returnTypes[i].getExpr()];
      ExprMap<unsigned>::iterator c_it = c.begin(), c_end = c.end();
      thisWellFounded = false;
      for (; c_it != c_end; ++c_it) {
        const Expr& cons = (*c_it).first;
        if (cons.isWellFounded()) {
          thisWellFounded = true;
          continue;
        }
        Expr funType = cons.getType().getExpr();
        int j = 0;
        for (; j < funType.arity()-1; ++j) {
          if (isDatatype(funType[j]) && !funType[j].isWellFounded())
            break;
        }
        if (j == funType.arity()-1) {
          changed = true;
          cons.setWellFounded();
          thisWellFounded = true;
        }
      }
      if (!thisWellFounded) {
        if (firstNotWellFounded == -1) firstNotWellFounded = i;
      }
      else {
        if (!returnTypes[i].getExpr().isWellFounded()) {
          changed = true;
          returnTypes[i].getExpr().setWellFounded();
        }
      }
    }
  } while (changed);

  if (firstNotWellFounded >= 0) {
    // TODO: uninstall all ID's
    throw TypecheckException
      ("Datatype "+names[firstNotWellFounded]+" has no finite terms");
  }

}

Expr TheoryDatatype::datatypeConsExpr(const string& constructor,
                                      const vector<Expr>& args)
{
  Expr e = resolveID(constructor);
  if (e.isNull())
    throw Exception("datatype: unknown constructor: "+constructor);
  if (!(e.isSymbol() && e.getKind() == CONSTRUCTOR))
    throw Exception("datatype: "+constructor+" resolves to: "+e.toString()+
                    "\nwhich is not a constructor");
  if (args.size() == 0) return e;
  return Expr(e.mkOp(), args);
}


Expr TheoryDatatype::datatypeSelExpr(const string& selector, const Expr& arg)
{
  Expr e = resolveID(selector);
  if (e.isNull())
    throw Exception("datatype: unknown selector: "+selector);
  if (!(e.isSymbol() && e.getKind() == SELECTOR))
    throw Exception("datatype: "+selector+" resolves to: "+e.toString()+
                    "\nwhich is not a selector");
  return Expr(e.mkOp(), arg);
}


Expr TheoryDatatype::datatypeTestExpr(const string& constructor, const Expr& arg)
{
  Expr e = resolveID("is_"+constructor);
  if (e.isNull())
    throw Exception("datatype: unknown tester: id_"+constructor);
  if (!(e.isSymbol() && e.getKind() == TESTER))
    throw Exception("datatype: is_"+constructor+" resolves to: "+e.toString()+
                    "\nwhich is not a tester");
  return Expr(e.mkOp(), arg);
}


const pair<Expr,unsigned>& TheoryDatatype::getSelectorInfo(const Expr& e)
{
  DebugAssert(e.getKind() == SELECTOR, "getSelectorInfo called on non-selector: "
              +e.toString());
  DebugAssert(d_selectorMap.find(e) != d_selectorMap.end(),
              "Unknown selector: "+e.toString());
  return d_selectorMap[e];
}


Expr TheoryDatatype::getConsForTester(const Expr& e)
{
  DebugAssert(e.getKind() == TESTER,
              "getConsForTester called on non-tester"
              +e.toString());
  DebugAssert(d_testerMap.find(e) != d_testerMap.end(),
              "Unknown tester: "+e.toString());
  return d_testerMap[e];
}


unsigned TheoryDatatype::getConsPos(const Expr& e)
{
  DebugAssert(e.getKind() == CONSTRUCTOR,
              "getConsPos called on non-constructor");
  Type t = e.getType();
  if (t.isFunction()) t = t[t.arity()-1];
  DebugAssert(isDatatype(t), "Expected datatype");
  DebugAssert(d_datatypes.find(t.getExpr()) != d_datatypes.end(),
              "Could not find datatype: "+t.toString());
  ExprMap<unsigned>& constMap = d_datatypes[t.getExpr()];
  DebugAssert(constMap.find(e) != constMap.end(),
              "Could not find constructor: "+e.toString());
  return constMap[e];
}


Expr TheoryDatatype::getConstant(const Type& t)
{
  if (isDatatype(t)) {
   DebugAssert(d_datatypes.find(t.getExpr()) != d_datatypes.end(),
               "Unknown datatype: "+t.getExpr().toString());
   ExprMap<unsigned>& c = d_datatypes[t.getExpr()];
   ExprMap<unsigned>::iterator i = c.begin(), iend = c.end();
   for (; i != iend; ++i) {
     const Expr& cons = (*i).first;
     if (!cons.isWellFounded()) continue;
     if (!cons.getType().isFunction()) return cons;
     Expr funType = cons.getType().getExpr();
     vector<Expr> args;
     for (int j = 0; j < funType.arity()-1; ++j) {
       Type t_j = Type(funType[j]);
       args.push_back(getConstant(t_j));
     }
     return Expr(cons.mkOp(), args);
   }
   DebugAssert(false, "Couldn't find well-founded constructor for"
               +t.toString());
  }
  DebugAssert(!t.isBool() && !t.isFunction(),
              "Expected non-bool, non-function type");
  string name = "datatype_"+t.getExpr().toString();
  Expr e = resolveID(name);
  if (e.isNull()) return newVar(name, t);
  return e;
}

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