Add the sequence datatype (#4153)

This class is the Node-level representation of a sequence. It is analogous to CVC4::String.

1 files changed, 168 insertions, 0 deletions

diff --git a/src/expr/sequence.h b/src/expr/sequence.h
new file mode 100644
index 000000000..833e79441
--- /dev/null
+++ b/src/expr/sequence.h
@@ -0,0 +1,168 @@
+/*********************                                                        */
+/*! \file sequence.h
+ ** \verbatim
+ ** Top contributors (to current version):
+ **   Andrew Reynolds
+ ** 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 The sequence data type.
+ **/
+
+#include "cvc4_private.h"
+
+#ifndef CVC4__EXPR__SEQUENCE_H
+#define CVC4__EXPR__SEQUENCE_H
+
+#include <vector>
+#include "expr/node.h"
+
+namespace CVC4 {
+
+class ExprSequence;
+
+/** The CVC4 sequence class
+ *
+ * This data structure is the domain of values for the sequence type.
+ */
+class Sequence
+{
+ public:
+  /** constructors for Sequence
+   *
+   * Internally, a CVC4::Sequence is represented by a vector of Nodes (d_seq),
+   * where each Node in this vector must be a constant.
+   */
+  Sequence() = default;
+  explicit Sequence(TypeNode t, const std::vector<Node>& s);
+
+  Sequence& operator=(const Sequence& y);
+
+  Sequence concat(const Sequence& other) const;
+
+  bool operator==(const Sequence& y) const { return cmp(y) == 0; }
+  bool operator!=(const Sequence& y) const { return cmp(y) != 0; }
+  bool operator<(const Sequence& y) const { return cmp(y) < 0; }
+  bool operator>(const Sequence& y) const { return cmp(y) > 0; }
+  bool operator<=(const Sequence& y) const { return cmp(y) <= 0; }
+  bool operator>=(const Sequence& y) const { return cmp(y) >= 0; }
+
+  bool strncmp(const Sequence& y, size_t n) const;
+  bool rstrncmp(const Sequence& y, size_t n) const;
+
+  /** is this the empty sequence? */
+  bool empty() const { return d_seq.empty(); }
+  /** is less than or equal to sequence y */
+  bool isLeq(const Sequence& y) const;
+  /** Return the length of the sequence */
+  size_t size() const { return d_seq.size(); }
+
+  /** Return true if this sequence is a repetition of the same element */
+  bool isRepeated() const;
+
+  /**
+   * Return the first position y occurs in this sequence, or std::string::npos
+   * otherwise.
+   */
+  size_t find(const Sequence& y, size_t start = 0) const;
+  /**
+   * Return the first position y occurs in this sequence searching from the end,
+   * or std::string::npos otherwise.
+   */
+  size_t rfind(const Sequence& y, size_t start = 0) const;
+  /** Returns true if y is a prefix of this */
+  bool hasPrefix(const Sequence& y) const;
+  /** Returns true if y is a suffix of this */
+  bool hasSuffix(const Sequence& y) const;
+  /** Replace the first occurrence of s in this sequence with t */
+  Sequence replace(const Sequence& s, const Sequence& t) const;
+  /** Return the subsequence of this sequence starting at index i */
+  Sequence substr(size_t i) const;
+  /**
+   * Return the subsequence of this sequence starting at index i with size at
+   * most j.
+   */
+  Sequence substr(size_t i, size_t j) const;
+  /** Return the prefix of this sequence of size at most i */
+  Sequence prefix(size_t i) const { return substr(0, i); }
+  /** Return the suffix of this sequence of size at most i */
+  Sequence suffix(size_t i) const { return substr(size() - i, i); }
+
+  /**
+   * Checks if there is any overlap between this sequence and another sequence.
+   * This corresponds to checking whether one sequence contains the other and
+   * whether a subsequence of one is a prefix of the other and vice-versa.
+   *
+   * @param y The other sequence
+   * @return True if there is an overlap, false otherwise
+   */
+  bool noOverlapWith(const Sequence& y) const;
+
+  /** sequence overlap
+   *
+   * if overlap returns m>0,
+   * then the maximal suffix of this sequence that is a prefix of y is of length
+   * m.
+   *
+   * For example, if x is "abcdef", then:
+   * x.overlap("defg") = 3
+   * x.overlap("ab") = 0
+   * x.overlap("d") = 0
+   * x.overlap("bcdefdef") = 5
+   */
+  size_t overlap(const Sequence& y) const;
+  /** sequence reverse overlap
+   *
+   * if roverlap returns m>0,
+   * then the maximal prefix of this sequence that is a suffix of y is of length
+   * m.
+   *
+   * For example, if x is "abcdef", then:
+   * x.roverlap("aaabc") = 3
+   * x.roverlap("def") = 0
+   * x.roverlap("d") = 0
+   * x.roverlap("defabcde") = 5
+   *
+   * Notice that x.overlap(y) = y.roverlap(x)
+   */
+  size_t roverlap(const Sequence& y) const;
+
+  /** get type */
+  TypeNode getType() const { return d_type; }
+  /** get the internal Node representation of this sequence */
+  const std::vector<Node>& getVec() const { return d_seq; }
+  /** get the internal node value of the first element in this sequence */
+  Node front() const;
+  /** get the internal node value of the last element in this sequence */
+  Node back() const;
+  /**
+   * Returns the maximum sequence length representable by this class.
+   * Corresponds to the maximum size of d_seq.
+   */
+  static size_t maxSize();
+
+ private:
+  /**
+   * Returns a negative number if *this < y, 0 if *this and y are equal and a
+   * positive number if *this > y.
+   */
+  int cmp(const Sequence& y) const;
+  /** The element type of the sequence */
+  TypeNode d_type;
+  /** The data of the sequence */
+  std::vector<Node> d_seq;
+};
+
+struct SequenceHashFunction
+{
+  size_t operator()(const Sequence& s) const;
+};
+
+std::ostream& operator<<(std::ostream& os, const Sequence& s);
+
+}  // namespace CVC4
+
+#endif /* CVC4__EXPR__SEQUENCE_H */