knotkit/algebra/Zp.h
Wojciech Politarczyk 203477c3a8 First shot at periodicity congruences
Verification of Przytycki's congruence works fine, however there are
some small modifications that could be made.

The, naive, approach to the verification of periodicity congruence for
the Khovanov polynomial didn't work. There are just too many cases to
check. Generation of all of them can exhaust the memory.
2016-11-24 15:28:31 +01:00

128 lines
2.9 KiB
C++

#ifndef KNOTKIT_ALGEBRA_ZP_H
#define KNOTKIT_ALGEBRA_ZP_H
#include <algebra/Z.h>
#include <iostream>
#include <tuple>
#include <cassert>
template<unsigned p>
class Zp
{
public:
using linear_combination = ::linear_combination<Zp<p>>;
using linear_combination_const_iter = ::linear_combination_const_iter<Zp<p>>;
private:
unsigned v;
public:
Zp () : v(0) { }
Zp (unsigned init) : v(init % p) { }
Zp (int init)
{
int i = init % (int)p;
if (i < 0)
i += p;
assert (i >= 0 && i < (int)p);
v = i;
}
Zp (const Zp& x) : v(x.v) { }
Zp (copy, const Zp& x) : v(x.v) {}
Zp (Zp&& x) : v(std::move(x.v)) {
x.v = 0;
}
Zp (const Z& z) : v((z % p).get_ui()) {}
~Zp () { }
Zp& operator = (const Zp& x) { v = x.v; return *this; }
Zp& operator = (Zp&& x) { v = x.v; x.v = 0; return *this; }
Zp& operator = (int x)
{
return operator = (Zp (x));
}
bool operator == (const Zp& x) const { return v == x.v; }
bool operator != (const Zp& x) const { return !operator == (x); }
bool operator == (int x) const { return operator == (Zp (x)); }
bool operator != (int x) const { return !operator == (x); }
bool operator < (const Zp& x) const { return v < x.v; }
bool is_unit () const
{
return v != 0;
}
Zp operator + (const Zp& x) const { return Zp (v + x.v); }
Zp operator - (const Zp& x) const { return Zp ((int)v - (int)x.v); }
Zp operator - () const { return Zp (- (int)v); }
Zp operator * (const Zp& x) const { return Zp (v * x.v); }
Zp operator / (const Zp& x) const
{
return operator * (x.recip ());
}
Zp recip () const
{
std::tuple<unsigned, int, int> t = unsigned_extended_gcd (v, p);
assert (std::get<0> (t) == 1);
assert ((int)std::get<0> (t) == std::get<1> (t)*(int)v + std::get<2> (t)*(int)p);
return Zp (std::get<1> (t));
}
Zp& operator += (const Zp& x)
{
v = (v + x.v) % p;
return *this;
}
Zp& operator -= (const Zp& x) { return operator = (Zp ((int)v - (int)x.v)); }
Zp& operator *= (const Zp& x)
{
v = (v * x.v) % p;
return *this;
}
Zp& operator /= (const Zp& x)
{
return operator *= (x.recip ());
}
// d | n, d.divides (n)
bool divides (const Zp& n) const
{
return v || !n.v;
}
bool operator | (const Zp& n) const { return divides (n); }
Zp div (const Zp& d) const { return operator / (d); }
std::tuple<Zp, Zp, Zp> extended_gcd (const Zp &x) const
{
if (v)
return std::make_tuple (v, Zp (1), Zp (0));
else
return std::make_tuple (x, Zp (0), Zp (1));
}
Zp gcd (const Zp &x) const
{
assert (v || x.v);
return 1;
}
friend std::ostream& operator << (std::ostream& os, const Zp& x) {
return os << x.v;
}
static void show_ring () { std::cout << "Z" << p; }
void show_self () const { std::cout << v << "(" << p << ")"; }
void display_self () const { std::cout << *this << "\n"; }
};
#endif //KNOTKIT_ALGEBRA_ZP_H