frac.hpp

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// Copyright 1996 Michael E. Stillman.
#ifndef _frac_hh_
#define _frac_hh_

 
#include "monoid.hpp"
#include "ring.hpp"
#include "polyring.hpp"
 
struct frac_elem
{
  ring_elem numer;
  ring_elem denom;
};

class FractionField : public Ring
{
  const PolyRingFlat *R_;  // Base ring.  Assumed to be a domain.
  bool use_gcd_simplify;   // Use built in gcd only if this is frac(ZZ[xs]) or
                           // frac(ZZ/p[xs])
  // When we (if we) change fractions to be flat, then this
  // restriction should go away.
 
  ring_elem set_non_unit_frac(ring_elem top) const;
  frac_elem *new_frac_elem() const;
  void simplify(frac_elem *f) const;
  frac_elem *make_elem(ring_elem a, ring_elem b) const;
 
 protected:
  FractionField() {}
  virtual ~FractionField() {}
  bool initialize_frac(const PolyRingFlat *R);
 
 public:
  static FractionField *create(const PolyRingFlat *R);
 
  FractionField *cast_to_FractionField() { return this; }
  const FractionField *cast_to_FractionField() const { return this; }
  const Ring *get_ring() const { return R_; }
  unsigned long get_precision() const { return R_->get_precision(); }
  ring_elem numerator(ring_elem f) const;
  ring_elem denominator(ring_elem f) const;
  ring_elem fraction(const ring_elem top, const ring_elem bottom) const;
 
  // The following are all the routines required by 'ring'
  virtual bool is_fraction_field() const { return true; }
  virtual bool is_graded() const { return R_->is_graded(); }
  virtual CoefficientType coefficient_type() const;
  virtual int n_fraction_vars() const;
 
  virtual void text_out(buffer &o) const;
 
  virtual unsigned int computeHashValue(const ring_elem a) const;
 
  virtual ring_elem from_long(long n) const;
  virtual ring_elem from_int(mpz_srcptr n) const;
  virtual bool from_rational(mpq_srcptr n, ring_elem &result) const;
  virtual ring_elem var(int v) const;
 
  virtual int index_of_var(const ring_elem a) const;
  virtual M2_arrayint support(const ring_elem a) const;
 
  void lower_content(ring_elem &c, const ring_elem g) const;
 
  virtual bool promote(const Ring *R,
                       const ring_elem f,
                       ring_elem &result) const;
  virtual bool lift(const Ring *R, const ring_elem f, ring_elem &result) const;
 
  virtual bool is_unit(const ring_elem f) const;
  virtual bool is_zero(const ring_elem f) const;
  virtual bool is_equal(const ring_elem f, const ring_elem g) const;
  virtual int compare_elems(const ring_elem f, const ring_elem g) const;
 
  virtual bool is_homogeneous(const ring_elem f) const;
  virtual bool multi_degree(const ring_elem f, monomial d) const;
  virtual void degree_weights(const ring_elem f,
                              const std::vector<int> &wts,
                              int &lo,
                              int &hi) const;
  virtual ring_elem homogenize(const ring_elem f,
                               int v,
                               int deg,
                               const std::vector<int> &wts) const;
  virtual ring_elem homogenize(const ring_elem f,
                               int v,
                               const std::vector<int> &wts) const;
 
  virtual ring_elem copy(const ring_elem f) const;
  virtual void remove(ring_elem &f) const;
 
  void internal_negate_to(ring_elem &f) const;
  void internal_add_to(ring_elem &f, ring_elem &g) const;
  void internal_subtract_to(ring_elem &f, ring_elem &g) const;
 
  virtual ring_elem negate(const ring_elem f) const;
  virtual ring_elem add(const ring_elem f, const ring_elem g) const;
  virtual ring_elem subtract(const ring_elem f, const ring_elem g) const;
  virtual ring_elem mult(const ring_elem f, const ring_elem g) const;
  virtual ring_elem power(const ring_elem f, mpz_srcptr n) const;
  virtual ring_elem power(const ring_elem f, int n) const;
  virtual ring_elem invert(const ring_elem f) const;
  virtual ring_elem divide(const ring_elem f, const ring_elem g) const;
 
  virtual void syzygy(const ring_elem a,
                      const ring_elem b,
                      ring_elem &x,
                      ring_elem &y) const;
 
  virtual ring_elem random() const;
 
  virtual void elem_text_out(buffer &o,
                             const ring_elem f,
                             bool p_one = true,
                             bool p_plus = false,
                             bool p_parens = false) const;
 
  virtual ring_elem eval(const RingMap *map,
                         const ring_elem f,
                         int first_var) const;
 
  virtual int n_terms(const ring_elem f) const;
  virtual ring_elem term(const ring_elem a, const_monomial m) const;
  virtual ring_elem lead_coeff(const ring_elem f) const;
  virtual ring_elem get_coeff(const ring_elem f, const_monomial m) const;
  virtual ring_elem get_terms(int nvars0,
                              const ring_elem f,
                              int lo,
                              int hi) const;
};
 
#endif
 
// Local Variables:
// compile-command: "make -C $M2BUILDDIR/Macaulay2/e "
// indent-tabs-mode: nil
// End: