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/******************************************************************************
* Top contributors (to current version):
* Andrew Reynolds
*
* 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.
* ****************************************************************************
*
* Utilities for constructing canonical terms.
*/
#include "cvc5_private.h"
#ifndef CVC5__EXPR__TERM_CANONIZE_H
#define CVC5__EXPR__TERM_CANONIZE_H
#include <map>
#include "expr/node.h"
namespace cvc5 {
namespace expr {
/** TermCanonize
*
* This class contains utilities for canonizing terms with respect to
* free variables (which are of kind BOUND_VARIABLE). For example, this
* class infers that terms like f(BOUND_VARIABLE_1) and f(BOUND_VARIABLE_2)
* are effectively the same term.
*/
class TermCanonize
{
public:
TermCanonize();
~TermCanonize() {}
/** Maps operators to an identifier, useful for ordering. */
int getIdForOperator(Node op);
/** Maps types to an identifier, useful for ordering. */
int getIdForType(TypeNode t);
/** get term order
*
* Returns true if a <= b in the term ordering used by this class. The
* term order is determined by the leftmost position in a and b whose
* operators o_a and o_b are distinct at that position. Then a <= b iff
* getIdForOperator( o_a ) <= getIdForOperator( o_b ).
*/
bool getTermOrder(Node a, Node b);
/** get canonical free variable #i of type tn */
Node getCanonicalFreeVar(TypeNode tn, unsigned i);
/** get canonical term
*
* This returns a canonical (alpha-equivalent) version of n, where
* bound variables in n may be replaced by other ones, and arguments of
* commutative operators of n may be sorted (if apply_torder is true). If
* doHoVar is true, we also canonicalize bound variables that occur in
* operators.
*
* In detail, we replace bound variables in n so the the leftmost occurrence
* of a bound variable for type T is the first canonical free variable for T,
* the second leftmost is the second, and so on, for each type T.
*/
Node getCanonicalTerm(TNode n,
bool apply_torder = false,
bool doHoVar = true);
private:
/** the number of ids we have allocated for operators */
int d_op_id_count;
/** map from operators to id */
std::map<Node, int> d_op_id;
/** the number of ids we have allocated for types */
int d_typ_id_count;
/** map from type to id */
std::map<TypeNode, int> d_typ_id;
/** free variables for each type */
std::map<TypeNode, std::vector<Node> > d_cn_free_var;
/**
* Map from each free variable above to their index in their respective vector
*/
std::map<Node, size_t> d_fvIndex;
/**
* Return the range of the free variable in the above map, or 0 if it does not
* exist.
*/
size_t getIndexForFreeVariable(Node v) const;
/** get canonical term
*
* This is a helper function for getCanonicalTerm above. We maintain a
* counter of how many variables we have allocated for each type (var_count),
* and a cache of visited nodes (visited).
*/
Node getCanonicalTerm(TNode n,
bool apply_torder,
bool doHoVar,
std::map<TypeNode, unsigned>& var_count,
std::map<TNode, Node>& visited);
};
} // namespace expr
} // namespace cvc5
#endif /* CVC5__EXPR__TERM_CANONIZE_H */
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