action_on_sign.cpp

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// action_on_sign.cpp
//
// Anton Betten
// August 12, 2016
 
#include "foundations/foundations.h"
#include "group_actions.h"
 
using namespace std;
 
 
namespace orbiter {
namespace layer3_group_actions {
namespace induced_actions {
 
 
action_on_sign::action_on_sign()
{
    null();
}
 
action_on_sign::~action_on_sign()
{
    free();
}
 
void action_on_sign::null()
{
    perm = NULL;
}
 
void action_on_sign::free()
{   
    if (perm) {
        FREE_int(perm);
        }
    null();
}
 
 
void action_on_sign::init(actions::action *A, int verbose_level)
{
    int f_v = (verbose_level >= 1);
    ring_theory::longinteger_object go;
    
    if (f_v) {
        cout << "action_on_sign::init" << endl;
        }
    action_on_sign::A = A;
    perm_degree = A->degree;
    if (f_v) {
        cout << "perm_degree=" << perm_degree << endl;
        }
    perm = NEW_int(perm_degree);
    degree = 2;
    
    if (f_v) {
        cout << "action_on_sign::init" << endl;
        }
}
 
long int action_on_sign::compute_image(int *Elt,
        long int i, int verbose_level)
{
    int f_v = (verbose_level >= 1);
    long int u, v, sgn, j;
    combinatorics::combinatorics_domain Combi;
    
    if (f_v) {
        cout << "action_on_sign::compute_image "
                "i = " << i << endl;
        }
    if (i < 0 || i >= degree) {
        cout << "action_on_sign::compute_image "
                "i = " << i << " out of range" << endl;
        exit(1);
        }
    for (u = 0; u < perm_degree; u++) {
        v = A->element_image_of(u, Elt, FALSE);
        perm[u] = v;
        }
    sgn = Combi.perm_signum(perm, perm_degree);
    if (sgn == -1) {
        j = (i + 1) % 2;
        }
    else {
        j = i;
        }
    
    if (f_v) {
        cout << "action_on_sign::compute_image "
                "image of " << i << " is " << j << endl;
        }
    return j;
}
 
}}}