/*********************                                                        */
/*! \file parser.h
 ** \verbatim
 ** Top contributors (to current version):
 **   Morgan Deters, Andrew Reynolds, Christopher L. Conway
 ** This file is part of the CVC4 project.
 ** Copyright (c) 2009-2019 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.\endverbatim
 **
 ** \brief A collection of state for use by parser implementations.
 **
 ** A collection of state for use by parser implementations.
 **/

#include "cvc4parser_public.h"

#ifndef __CVC4__PARSER__PARSER_STATE_H
#define __CVC4__PARSER__PARSER_STATE_H

#include <string>
#include <set>
#include <list>
#include <cassert>

#include "expr/expr.h"
#include "expr/expr_stream.h"
#include "expr/kind.h"
#include "expr/symbol_table.h"
#include "parser/input.h"
#include "parser/parser_exception.h"
#include "util/unsafe_interrupt_exception.h"

namespace CVC4 {

// Forward declarations
class BooleanType;
class Command;
class FunctionType;
class Type;
class ResourceManager;
namespace api {
class Solver;
}

//for sygus gterm two-pass parsing
class CVC4_PUBLIC SygusGTerm {
public:
  enum{
    gterm_op,
    gterm_let,
    gterm_constant,
    gterm_variable,
    gterm_input_variable,
    gterm_local_variable,
    gterm_nested_sort,
    gterm_unresolved,
    gterm_ignore,
  };
  Type d_type;
  Expr d_expr;
  std::vector< Expr > d_let_vars;
  unsigned d_gterm_type;
  std::string d_name;
  std::vector< SygusGTerm > d_children;
  
  unsigned getNumChildren() { return d_children.size(); }
  void addChild(){
    d_children.push_back( SygusGTerm() );
  }
};

namespace parser {

class Input;

/** Types of checks for the symbols */
enum DeclarationCheck {
  /** Enforce that the symbol has been declared */
  CHECK_DECLARED,
  /** Enforce that the symbol has not been declared */
  CHECK_UNDECLARED,
  /** Don't check anything */
  CHECK_NONE
};/* enum DeclarationCheck */

/**
 * Returns a string representation of the given object (for
 * debugging).
 */
inline std::ostream& operator<<(std::ostream& out, DeclarationCheck check) CVC4_PUBLIC;
inline std::ostream& operator<<(std::ostream& out, DeclarationCheck check) {
  switch(check) {
  case CHECK_NONE:
    return out << "CHECK_NONE";
  case CHECK_DECLARED:
    return out << "CHECK_DECLARED";
  case CHECK_UNDECLARED:
    return out << "CHECK_UNDECLARED";
  default:
    return out << "DeclarationCheck!UNKNOWN";
  }
}

/**
 * Types of symbols. Used to define namespaces.
 */
enum SymbolType {
  /** Variables */
  SYM_VARIABLE,
  /** Sorts */
  SYM_SORT
};/* enum SymbolType */

/**
 * Returns a string representation of the given object (for
 * debugging).
 */
inline std::ostream& operator<<(std::ostream& out, SymbolType type) CVC4_PUBLIC;
inline std::ostream& operator<<(std::ostream& out, SymbolType type) {
  switch(type) {
  case SYM_VARIABLE:
    return out << "SYM_VARIABLE";
  case SYM_SORT:
    return out << "SYM_SORT";
  default:
    return out << "SymbolType!UNKNOWN";
  }
}

/**
 * This class encapsulates all of the state of a parser, including the
 * name of the file, line number and column information, and in-scope
 * declarations.
 */
class CVC4_PUBLIC Parser {
  friend class ParserBuilder;
private:
 /** The API Solver object. */
 api::Solver* d_solver;

 /** The resource manager associated with this expr manager */
 ResourceManager* d_resourceManager;

 /** The input that we're parsing. */
 Input* d_input;

 /**
  * The declaration scope that is "owned" by this parser.  May or
  * may not be the current declaration scope in use.
  */
 SymbolTable d_symtabAllocated;

 /**
  * This current symbol table used by this parser.  Initially points
  * to d_symtabAllocated, but can be changed (making this parser
  * delegate its definitions and lookups to another parser).
  * See useDeclarationsFrom().
  */
 SymbolTable* d_symtab;

 /**
  * The level of the assertions in the declaration scope.  Things declared
  * after this level are bindings from e.g. a let, a quantifier, or a
  * lambda.
  */
 size_t d_assertionLevel;

 /**
  * Whether we're in global declarations mode (all definitions and
  * declarations are global).
  */
 bool d_globalDeclarations;

 /**
  * Maintains a list of reserved symbols at the assertion level that might
  * not occur in our symbol table.  This is necessary to e.g. support the
  * proper behavior of the :named annotation in SMT-LIBv2 when used under
  * a let or a quantifier, since inside a let/quant body the declaration
  * scope is that of the let/quant body, but the defined name should be
  * reserved at the assertion level.
  */
 std::set<std::string> d_reservedSymbols;

 /** How many anonymous functions we've created. */
 size_t d_anonymousFunctionCount;

 /** Are we done */
 bool d_done;

 /** Are semantic checks enabled during parsing? */
 bool d_checksEnabled;

 /** Are we parsing in strict mode? */
 bool d_strictMode;

 /** Are we only parsing? */
 bool d_parseOnly;

 /**
  * Can we include files?  (Set to false for security purposes in
  * e.g. the online version.)
  */
 bool d_canIncludeFile;

 /**
  * Whether the logic has been forced with --force-logic.
  */
 bool d_logicIsForced;

 /**
  * The logic, if d_logicIsForced == true.
  */
 std::string d_forcedLogic;

 /** The set of operators available in the current logic. */
 std::set<Kind> d_logicOperators;

 /** The set of attributes already warned about. */
 std::set<std::string> d_attributesWarnedAbout;

 /**
  * The current set of unresolved types.  We can get by with this NOT
  * being on the scope, because we can only have one DATATYPE
  * definition going on at one time.  This is a bit hackish; we
  * depend on mkMutualDatatypeTypes() to check everything and clear
  * this out.
  */
 std::set<Type> d_unresolved;

 /**
  * "Preemption commands": extra commands implied by subterms that
  * should be issued before the currently-being-parsed command is
  * issued.  Used to support SMT-LIBv2 ":named" attribute on terms.
  *
  * Owns the memory of the Commands in the queue.
  */
 std::list<Command*> d_commandQueue;

 /** Lookup a symbol in the given namespace (as specified by the type).
  * Only returns a symbol if it is not overloaded, returns null otherwise.
  */
 Expr getSymbol(const std::string& var_name, SymbolType type);

protected:
 /**
  * Create a parser state.
  *
  * @attention The parser takes "ownership" of the given
  * input and will delete it on destruction.
  *
  * @param the solver API object
  * @param input the parser input
  * @param strictMode whether to incorporate strict(er) compliance checks
  * @param parseOnly whether we are parsing only (and therefore certain checks
  * need not be performed, like those about unimplemented features, @see
  * unimplementedFeature())
  */
 Parser(api::Solver* solver,
        Input* input,
        bool strictMode = false,
        bool parseOnly = false);

public:

  virtual ~Parser();

  /** Get the associated <code>ExprManager</code>. */
  ExprManager* getExprManager() const;

  /** Get the associated solver. */
  api::Solver* getSolver() const;

  /** Get the associated input. */
  inline Input* getInput() const {
    return d_input;
  }

  /** Deletes and replaces the current parser input. */
  void setInput(Input* input)  {
    delete d_input;
    d_input = input;
    d_input->setParser(*this);
    d_done = false;
  }

  /**
   * Check if we are done -- either the end of input has been reached, or some
   * error has been encountered.
   * @return true if parser is done
   */
  inline bool done() const {
    return d_done;
  }

  /** Sets the done flag */
  inline void setDone(bool done = true) {
    d_done = done;
  }

  /** Enable semantic checks during parsing. */
  void enableChecks() { d_checksEnabled = true; }

  /** Disable semantic checks during parsing. Disabling checks may lead to crashes on bad inputs. */
  void disableChecks() { d_checksEnabled = false; }

  /** Enable strict parsing, according to the language standards. */
  void enableStrictMode() { d_strictMode = true; }

  /** Disable strict parsing. Allows certain syntactic infelicities to
      pass without comment. */
  void disableStrictMode() { d_strictMode = false; }

  bool strictModeEnabled() { return d_strictMode; }

  void allowIncludeFile() { d_canIncludeFile = true; }
  void disallowIncludeFile() { d_canIncludeFile = false; }
  bool canIncludeFile() const { return d_canIncludeFile; }

  /** Expose the functionality from SMT/SMT2 parsers, while making
      implementation optional by returning false by default. */
  virtual bool logicIsSet() { return false; }

  void forceLogic(const std::string& logic) { assert(!d_logicIsForced); d_logicIsForced = true; d_forcedLogic = logic; }
  const std::string& getForcedLogic() const { return d_forcedLogic; }
  bool logicIsForced() const { return d_logicIsForced; }

  /**
   * Gets the variable currently bound to name.
   *
   * @param name the name of the variable
   * @return the variable expression
   * Only returns a variable if its name is not overloaded, returns null otherwise.
   */
  Expr getVariable(const std::string& name);

  /**
   * Gets the function currently bound to name.
   *
   * @param name the name of the variable
   * @return the variable expression
   * Only returns a function if its name is not overloaded, returns null otherwise.
   */
  Expr getFunction(const std::string& name);

  /**
   * Returns the expression that name should be interpreted as, based on the current binding.
   *
   * The symbol name should be declared.
   * This creates the expression that the string "name" should be interpreted as.
   * Typically this corresponds to a variable, but it may also correspond to
   * a nullary constructor or a defined function.
   * Only returns an expression if its name is not overloaded, returns null otherwise.
   */
  virtual Expr getExpressionForName(const std::string& name);
  
  /**
   * Returns the expression that name should be interpreted as, based on the current binding.
   *
   * This is the same as above but where the name has been type cast to t. 
   */
  virtual Expr getExpressionForNameAndType(const std::string& name, Type t);
  
  /**
   * Returns the kind that should be used for applications of expression fun, where
   * fun has "function-like" type, i.e. where checkFunctionLike(fun) returns true. 
   * Returns a parse error if fun does not have function-like type.
   * 
   * For example, this function returns
   *   APPLY_UF if fun has function type, 
   *   APPLY_CONSTRUCTOR if fun has constructor type.
   */
  Kind getKindForFunction(Expr fun);
  
  /**
   * Returns a sort, given a name.
   * @param sort_name the name to look up
   */
  Type getSort(const std::string& sort_name);

  /**
   * Returns a (parameterized) sort, given a name and args.
   */
  Type getSort(const std::string& sort_name,
               const std::vector<Type>& params);

  /**
   * Returns arity of a (parameterized) sort, given a name and args.
   */
  size_t getArity(const std::string& sort_name);

  /**
   * Checks if a symbol has been declared.
   * @param name the symbol name
   * @param type the symbol type
   * @return true iff the symbol has been declared with the given type
   */
  bool isDeclared(const std::string& name, SymbolType type = SYM_VARIABLE);

  /**
   * Checks if the declaration policy we want to enforce holds
   * for the given symbol.
   * @param name the symbol to check
   * @param check the kind of check to perform
   * @param type the type of the symbol
   * @param notes notes to add to a parse error (if one is generated)
   * @throws ParserException if checks are enabled and the check fails
   */
  void checkDeclaration(const std::string& name,
                        DeclarationCheck check,
                        SymbolType type = SYM_VARIABLE,
                        std::string notes = "");

  /**
   * Reserve a symbol at the assertion level.
   */
  void reserveSymbolAtAssertionLevel(const std::string& name);

  /**
   * Checks whether the given expression is function-like, i.e.
   * it expects arguments. This is checked by looking at the type 
   * of fun. Examples of function types are function, constructor,
   * selector, tester.
   * @param fun the expression to check
   * @throws ParserException if checks are enabled and fun is not
   * a function
   */
  void checkFunctionLike(Expr fun);

  /**
   * Check that <code>kind</code> can accept <code>numArgs</code> arguments.
   * @param kind the built-in operator to check
   * @param numArgs the number of actual arguments
   * @throws ParserException if checks are enabled and the operator
   * <code>kind</code> cannot be applied to <code>numArgs</code>
   * arguments.
   */
  void checkArity(Kind kind, unsigned numArgs);

  /**
   * Check that <code>kind</code> is a legal operator in the current
   * logic and that it can accept <code>numArgs</code> arguments.
   *
   * @param kind the built-in operator to check
   * @param numArgs the number of actual arguments
   * @throws ParserException if the parser mode is strict and the
   * operator <code>kind</code> has not been enabled
   */
  void checkOperator(Kind kind, unsigned numArgs);

  /** Create a new CVC4 variable expression of the given type. 
   *
   * flags specify information about the variable, e.g. whether it is global or defined
   *   (see enum in expr_manager_template.h).
   *
   * If a symbol with name already exists,
   *  then if doOverload is true, we create overloaded operators.
   *  else if doOverload is false, the existing expression is shadowed by the new expression.
   */
  Expr mkVar(const std::string& name, const Type& type,
             uint32_t flags = ExprManager::VAR_FLAG_NONE, 
             bool doOverload = false);

  /**
   * Create a set of new CVC4 variable expressions of the given type.
   *
   * flags specify information about the variable, e.g. whether it is global or defined
   *   (see enum in expr_manager_template.h).
   *
   * For each name, if a symbol with name already exists,
   *  then if doOverload is true, we create overloaded operators.
   *  else if doOverload is false, the existing expression is shadowed by the new expression.
   */
  std::vector<Expr>
    mkVars(const std::vector<std::string> names, const Type& type,
           uint32_t flags = ExprManager::VAR_FLAG_NONE, 
           bool doOverload = false);

  /** Create a new CVC4 bound variable expression of the given type. */
  Expr mkBoundVar(const std::string& name, const Type& type);

  /**
   * Create a set of new CVC4 bound variable expressions of the given type.
   *
   * flags specify information about the variable, e.g. whether it is global or defined
   *   (see enum in expr_manager_template.h).
   *
   * For each name, if a symbol with name already exists,
   *  then if doOverload is true, we create overloaded operators.
   *  else if doOverload is false, the existing expression is shadowed by the new expression.
   */
  std::vector<Expr> mkBoundVars(const std::vector<std::string> names, const Type& type);

  /** Create a new CVC4 function expression of the given type. */
  Expr mkFunction(const std::string& name, const Type& type,
                  uint32_t flags = ExprManager::VAR_FLAG_NONE, 
                  bool doOverload=false);

  /**
   * Create a new CVC4 function expression of the given type,
   * appending a unique index to its name.  (That's the ONLY
   * difference between mkAnonymousFunction() and mkFunction()).
   *
   * flags specify information about the variable, e.g. whether it is global or defined
   *   (see enum in expr_manager_template.h).
   */
  Expr mkAnonymousFunction(const std::string& prefix, const Type& type,
                           uint32_t flags = ExprManager::VAR_FLAG_NONE);

  /** Create a new variable definition (e.g., from a let binding). 
   * levelZero is set if the binding must be done at level 0.
   * If a symbol with name already exists,
   *  then if doOverload is true, we create overloaded operators.
   *  else if doOverload is false, the existing expression is shadowed by the new expression.
   */
  void defineVar(const std::string& name, const Expr& val,
                 bool levelZero = false, bool doOverload = false);

  /** Create a new function definition (e.g., from a define-fun). 
   * levelZero is set if the binding must be done at level 0.
   * If a symbol with name already exists,
   *  then if doOverload is true, we create overloaded operators.
   *  else if doOverload is false, the existing expression is shadowed by the new expression.
   */
  void defineFunction(const std::string& name, const Expr& val,
                      bool levelZero = false, bool doOverload = false);

  /** Create a new type definition. */
  void defineType(const std::string& name, const Type& type);

  /** Create a new (parameterized) type definition. */
  void defineType(const std::string& name,
                  const std::vector<Type>& params, const Type& type);

  /** Create a new type definition (e.g., from an SMT-LIBv2 define-sort). */
  void defineParameterizedType(const std::string& name,
                               const std::vector<Type>& params,
                               const Type& type);

  /**
   * Creates a new sort with the given name.
   */
  SortType mkSort(const std::string& name,
                  uint32_t flags = ExprManager::SORT_FLAG_NONE);

  /**
   * Creates a new sort constructor with the given name and arity.
   */
  SortConstructorType mkSortConstructor(
      const std::string& name,
      size_t arity,
      uint32_t flags = ExprManager::SORT_FLAG_NONE);

  /**
   * Creates a new "unresolved type," used only during parsing.
   */
  SortType mkUnresolvedType(const std::string& name);

  /**
   * Creates a new unresolved (parameterized) type constructor of the given
   * arity.
   */
  SortConstructorType mkUnresolvedTypeConstructor(const std::string& name, 
                                                  size_t arity);
  /**
   * Creates a new unresolved (parameterized) type constructor given the type
   * parameters.
   */
  SortConstructorType mkUnresolvedTypeConstructor(const std::string& name, 
                                                  const std::vector<Type>& params);

  /**
   * Returns true IFF name is an unresolved type.
   */
  bool isUnresolvedType(const std::string& name);

  /**
   * Create sorts of mutually-recursive datatypes.
   * For each symbol defined by the datatype, if a symbol with name already exists,
   *  then if doOverload is true, we create overloaded operators.
   *  else if doOverload is false, the existing expression is shadowed by the new expression.
   */
  std::vector<DatatypeType>
  mkMutualDatatypeTypes(std::vector<Datatype>& datatypes, bool doOverload=false);

  /** make flat function type
   *
   * Returns the "flat" function type corresponding to the function taking
   * argument types "sorts" and range type "range".  A flat function type is
   * one whose range is not a function. Notice that if sorts is empty and range
   * is not a function, then this function returns range itself.
   *
   * If range is a function type, we add its function argument sorts to sorts
   * and consider its function range as the new range. For each sort S added
   * to sorts in this process, we add a new bound variable of sort S to
   * flattenVars.
   *
   * For example:
   * mkFlattenFunctionType( { Int, (-> Real Real) }, (-> Int Bool), {} ):
   * - returns the the function type (-> Int (-> Real Real) Int Bool)
   * - updates sorts to { Int, (-> Real Real), Int },
   * - updates flattenVars to { x }, where x is bound variable of type Int.
   *
   * Notice that this method performs only one level of flattening, for example,
   * mkFlattenFunctionType({ Int, (-> Real Real) }, (-> Int (-> Int Bool)), {}):
   * - returns the the function type (-> Int (-> Real Real) Int (-> Int Bool))
   * - updates sorts to { Int, (-> Real Real), Int },
   * - updates flattenVars to { x }, where x is bound variable of type Int.
   *
   * This method is required so that we do not return functions
   * that have function return type (these give an unhandled exception
   * in the ExprManager). For examples of the equivalence between function
   * definitions in the proposed higher-order extension of the smt2 language,
   * see page 3 of http://matryoshka.gforge.inria.fr/pubs/PxTP2017.pdf.
   *
   * The argument flattenVars is needed in the case of defined functions
   * with function return type. These have implicit arguments, for instance:
   *    (define-fun Q ((x Int)) (-> Int Int) (lambda y (P x)))
   * is equivalent to the command:
   *    (define-fun Q ((x Int) (z Int)) Int (@ (lambda y (P x)) z))
   * where @ is (higher-order) application. In this example, z is added to
   * flattenVars.
   */
  Type mkFlatFunctionType(std::vector<Type>& sorts,
                          Type range,
                          std::vector<Expr>& flattenVars);

  /** make flat function type
   *
   * Same as above, but does not take argument flattenVars.
   * This is used when the arguments of the function are not important (for
   * instance, if we are only using this type in a declare-fun).
   */
  Type mkFlatFunctionType(std::vector<Type>& sorts, Type range);

  /** make higher-order apply
   *
   * This returns the left-associative curried application of (function) expr to
   * the arguments in args.
   *
   * For example, mkHoApply( f, { a, b }, 0 ) returns
   *  (HO_APPLY (HO_APPLY f a) b)
   *
   * If args is non-empty, the expected type of expr is (-> T0 ... Tn T), where
   *    args[i].getType() = Ti
   * for each i where 0 <= i < args.size(). If expr is not of this
   * type, the expression returned by this method will not be well typed.
   */
  Expr mkHoApply(Expr expr, std::vector<Expr>& args);

  /**
   * Add an operator to the current legal set.
   *
   * @param kind the built-in operator to add
   */
  void addOperator(Kind kind);

  /**
   * Preempt the next returned command with other ones; used to
   * support the :named attribute in SMT-LIBv2, which implicitly
   * inserts a new command before the current one. Also used in TPTP
   * because function and predicate symbols are implicitly declared.
   */
  void preemptCommand(Command* cmd);

  /** Is the symbol bound to a boolean variable? */
  bool isBoolean(const std::string& name);

  /** Is fun a function (or function-like thing)? 
  * Currently this means its type is either a function, constructor, tester, or selector.
  */
  bool isFunctionLike(Expr fun);

  /** Is the symbol bound to a defined function? */
  bool isDefinedFunction(const std::string& name);

  /** Is the Expr a defined function? */
  bool isDefinedFunction(Expr func);

  /** Is the symbol bound to a predicate? */
  bool isPredicate(const std::string& name);

  /** Parse and return the next command. */
  Command* nextCommand();

  /** Parse and return the next expression. */
  Expr nextExpression();

  /** Issue a warning to the user. */
  void warning(const std::string& msg) { d_input->warning(msg); }
  /** Issue a warning to the user, but only once per attribute. */
  void attributeNotSupported(const std::string& attr);

  /** Raise a parse error with the given message. */
  inline void parseError(const std::string& msg) { d_input->parseError(msg); }
  /** Unexpectedly encountered an EOF */
  inline void unexpectedEOF(const std::string& msg)
  {
    d_input->parseError(msg, true);
  }

  /**
   * If we are parsing only, don't raise an exception; if we are not,
   * raise a parse error with the given message.  There is no actual
   * parse error, everything is as expected, but we cannot create the
   * Expr, Type, or other requested thing yet due to internal
   * limitations.  Even though it's not a parse error, we throw a
   * parse error so that the input line and column information is
   * available.
   *
   * Think quantifiers.  We don't have a TheoryQuantifiers yet, so we
   * have no kind::FORALL or kind::EXISTS.  But we might want to
   * support parsing quantifiers (just not doing anything with them).
   * So this mechanism gives you a way to do it with --parse-only.
   */
  inline void unimplementedFeature(const std::string& msg)
  {
    if(!d_parseOnly) {
      parseError("Unimplemented feature: " + msg);
    }
  }

  /**
   * Gets the current declaration level.
   */
  inline size_t scopeLevel() const { return d_symtab->getLevel(); }

  inline void pushScope(bool bindingLevel = false) {
    d_symtab->pushScope();
    if(!bindingLevel) {
      d_assertionLevel = scopeLevel();
    }
  }

  inline void popScope() {
    d_symtab->popScope();
    if(scopeLevel() < d_assertionLevel) {
      d_assertionLevel = scopeLevel();
      d_reservedSymbols.clear();
    }
  }

  virtual void reset() {
    d_symtab->reset();
  }

  void setGlobalDeclarations(bool flag) {
    d_globalDeclarations = flag;
  }

  /**
   * Set the current symbol table used by this parser.
   * From now on, this parser will perform its definitions and
   * lookups in the declaration scope of the "parser" argument
   * (but doesn't re-delegate if the other parser's declaration scope
   * changes later).  A NULL argument restores this parser's
   * "primordial" declaration scope assigned at its creation.  Calling
   * p->useDeclarationsFrom(p) is a no-op.
   *
   * This feature is useful when e.g. reading out-of-band expression data:
   * 1. Parsing --replay log files produced with --replay-log.
   * 2. Perhaps a multi-query benchmark file is being single-stepped
   *    with intervening queries on stdin that must reference the same
   *    declaration scope(s).
   *
   * However, the feature must be used carefully.  Pushes and pops
   * should be performed with the correct current declaration scope.
   * Care must be taken to match up declaration scopes, of course;
   * If variables in the deferred-to parser go out of scope, the
   * secondary parser will give errors that they are undeclared.
   * Also, an outer-scope variable shadowed by an inner-scope one of
   * the same name may be temporarily inaccessible.
   *
   * In short, caveat emptor.
   */
  inline void useDeclarationsFrom(Parser* parser) {
    if(parser == NULL) {
      d_symtab = &d_symtabAllocated;
    } else {
      d_symtab = parser->d_symtab;
    }
  }

  inline void useDeclarationsFrom(SymbolTable* symtab) {
    d_symtab = symtab;
  }

  inline SymbolTable* getSymbolTable() const {
    return d_symtab;
  }

  /**
   * An expression stream interface for a parser.  This stream simply
   * pulls expressions from the given Parser object.
   *
   * Here, the ExprStream base class allows a Parser (from the parser
   * library) and core components of CVC4 (in the core library) to
   * communicate without polluting the public interface or having them
   * reach into private (undocumented) interfaces.
   */
  class ExprStream : public CVC4::ExprStream {
    Parser* d_parser;
  public:
    ExprStream(Parser* parser) : d_parser(parser) {}
    ~ExprStream() { delete d_parser; }
    Expr nextExpr() override { return d_parser->nextExpression(); }
  };/* class Parser::ExprStream */
  
  //------------------------ operator overloading
  /** is this function overloaded? */
  bool isOverloadedFunction(Expr fun) {
    return d_symtab->isOverloadedFunction(fun);
  }
  
  /** Get overloaded constant for type.
   * If possible, it returns a defined symbol with name
   * that has type t. Otherwise returns null expression.
  */
  Expr getOverloadedConstantForType(const std::string& name, Type t) {
    return d_symtab->getOverloadedConstantForType(name, t);
  }
  
  /**
   * If possible, returns a defined function for a name
   * and a vector of expected argument types. Otherwise returns
   * null expression.
   */
  Expr getOverloadedFunctionForTypes(const std::string& name, std::vector< Type >& argTypes) {
    return d_symtab->getOverloadedFunctionForTypes(name, argTypes);
  }
  //------------------------ end operator overloading
};/* class Parser */

}/* CVC4::parser namespace */
}/* CVC4 namespace */

#endif /* __CVC4__PARSER__PARSER_STATE_H */