montable.hpp

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#ifndef __montable_h
#define __montable_h

 
#include "mem.hpp"
#include <vector>
#include <memory>
#include <algorithm>
#include <stdio.h>
#include <stddef.h>
 
#include "ExponentVector.hpp"
#include "newdelete.hpp"
#include "style.hpp"
 
/* "Tricks" used in this implementation */
/*
 1. exponent vectors: these look like: [e1, ..., en],
    where n is the number of variables.  HOWEVER, these
    exponents are never created or freed by these routines,
    so if they have more entries (e.g. a "sugar" homogenization)
    then that (those) value(s) are ignored.
 2. comparison routine: elements are kept in (increasing?) lex order.
    Is this really an OK idea?
 */

class MonomialTable : public our_new_delete
{
  static MonomialTable *make_minimal(int nvars,
                                     const VECTOR(exponents_t) & exps,
                                     const VECTOR(int) & comps,
                                     const VECTOR(int) & vals,
                                     VECTOR(int) & rejects);
 
  static void minimalize(int nvars,
                         const VECTOR(exponents_t) & exps,
                         const VECTOR(int) & comps,
                         bool keep_duplicates,
                         VECTOR(int) & result_positions);
 
  MonomialTable();  // the public must use "make" below
 public:
  struct mon_term
  {
    mon_term *_next;
    mon_term *_prev;
    exponents_t _lead; /* Who owns this? */
    unsigned long _mask;
    int _val;
  };
 
  static MonomialTable *make(
      int nvars);  // this function serves as the constructor
  /* Create a zero element table */
 
  ~MonomialTable();
 
  void insert(exponents_t exp, int comp, int id);
  /* Insert [exp,comp,id] into the table.  If there is already
     an element which is <= [exp,comp], this triple is still
     inserted.  If that is not desired, use find_divisors.
  */
 
  int find_divisor(exponents_t exp, int comp);
  /* returns the integer 'val' of the first divisor of exp*comp found,
     or, returns -1 if none is found. */
 
  int find_divisors(int max,
                    exponents_t exp,
                    int comp,
                    VECTOR(mon_term *) *result = nullptr);
  /* max: the max number of divisors to find.
     exp: the monomial whose divisors we seek.
     result: an array of mon_term's.
     return value: length of this array, i.e. the number of matches found */
 
  mon_term *find_exact(exponents_t exp, int comp) const;
  /* If this returns non-NULL, it is valid to grab the 'val' field, and/or to
     assign to it.
     All other fields should be considered read only */
 
  /* Need a way of looping through the elements? */
 
  void show(FILE *fil); /* Only for debugging */
 
 private:
  stash *mon_term_stash;
  int _nvars;
  int _count;
  VECTOR(mon_term *) _head; /* One per component */
  mon_term *_last_match;    // optimization cache for find_divisors
  int _last_match_comp;     // optimization cache for find_divisors
  mon_term *make_list_head();
  static void move_up(mon_term *const y, mon_term *const head);
  static void insert_before(mon_term *const y, mon_term *const z);
  static void remove(mon_term *const y);
};
 
#endif
 
// Local Variables:
// compile-command: "make -C $M2BUILDDIR/Macaulay2/e "
// indent-tabs-mode: nil
// End: