schur.hpp

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// Copyright 1996-2011 Michael E. Stillman
 
#ifndef _Schurring_hh_
#define _Schurring_hh_

 
#include <vector>
#include "poly.hpp"
 
const int SCHUR_MAX_WT = 100;
const int LARGE_NUMBER = 32000;
 
class tableau
{
  friend class SchurRing;
 
  int dim;
  int maxwt;
  int wt;
  int *lambda;  // A partition vector 0..nvars-1
  int *p;       // A partition vector 0..nvars-1
  int *xloc;    // array 1..|p|-|lambda| of the horizontal location
                // of this number in the skew table
  int *yloc;    // array 1..|p|-|lambda| of the vertical location
                // of this number in the skew table
 
  void initialize(int nvars);
  tableau() {}
  ~tableau() {}
  void resize(int max_wt);
 
  int elem(int x, int y) const;
  void fill(int *lamb, int *pp);
  void display() const;
};

class SchurRing : public PolyRing
{
 private:
  // These are variables that are used in the recursive routine
  // SM(), which is called from skew_schur().
  tableau _SMtab;
  tableau _SMfilled;
  int _SMcurrent;
  int _SMfinalwt;
  Nterm *_SMresult;
 
  void to_partition(const int *m, int *exp) const;
  // exp[1]..exp[nvars] are set
  void from_partition(const int *exp, int *m) const;
 
  void bounds(int &lo, int &hi);
  void SM();
  Nterm *skew_schur(int *lambda, int *p);
  ring_elem mult_monomials(const int *m, const int *n);
 
 protected:
  bool initialize_schur();
  SchurRing() {}
  virtual ~SchurRing() {}
 public:
  static SchurRing *create(const PolynomialRing *R);
 
  static SchurRing *create(const Ring *A, int n);
 
  static SchurRing *createInfinite(const Ring *A);
 
  virtual const SchurRing *cast_to_SchurRing() const { return this; }
  virtual SchurRing *cast_to_SchurRing() { return this; }
  virtual void text_out(buffer &o) 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;
 
  void dimension(const int *exp, mpz_t result) const;
  ring_elem dimension(const ring_elem f) const;
 
  virtual ring_elem mult_by_term(const ring_elem f,
                                 const ring_elem c,
                                 const int *m) const;
 
  ring_elem power(const ring_elem f, mpz_srcptr n) const;
  ring_elem power(const ring_elem f, int n) const;
};
 
#endif
 
// Local Variables:
// compile-command: "make -C $M2BUILDDIR/Macaulay2/e "
// indent-tabs-mode: nil
// End: