Permutations.hh

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#pragma once

#include <stdexcept>
#include <vector>


class PermutationException : std::logic_error {
    public:
        PermutationException(const std::string& ex) : std::logic_error(ex) {};
};

class Perm {
    public:
        std::vector<int> perm;

        template<class iterator>
        void find(iterator start1, iterator end1, iterator start2, iterator end2);

        template<class iterator>
        void apply(iterator start1, iterator end1);

};

class Images {
    public:
        std::vector<int> images;

        template<class iterator>
        void find(iterator start1, iterator end1, iterator start2, iterator end2);
};




template<class iterator>
void Perm::find(iterator start1, iterator end1, iterator start2, iterator end2)
    {
    perm.clear();

    while(start2!=end2) {
        auto it=start1;
        int num=0;
        while(it!=end1) {
            if(*start2==*it) {
                perm.push_back(num);
                break;
                }
            ++num;
            ++it;
            }
        if(it==end1)
            throw PermutationException("Sets do not contain the same elements.");
        
        ++start2;
        }
    }

template<class iterator>
void Perm::apply(iterator start, iterator end)
    {
    typedef typename std::remove_reference<decltype(*start)>::type value_type;

    std::vector<value_type> orig;
    auto it=start;
    while(it!=end) {
        orig.push_back(*it);
        ++it;
        }

    // std::cerr << orig.size() << ", " << perm.size() << std::endl;
    if(orig.size()!=perm.size()) {
        std::cerr << "Perm::apply: orig.size()=" << orig.size() << ", "
                     << "perm.size()=" << perm.size() << std::endl;
        assert(orig.size()==perm.size());
        }

    for(unsigned int i=0; i<orig.size(); ++i) {
        *start=orig[perm[i]];
        ++start;
        }
    }


template<class iterator>
void Images::find(iterator start1, iterator end1, iterator start2, iterator end2)
    {
    images.clear();

    while(start1!=end1) {
        auto it=start2;
        int num=0;
        while(it!=end2) {
            if(*start1==*it) {
                images.push_back(num);
                break;
                }
            ++num;
            ++it;
            }
        if(it==end2)
            throw PermutationException("Sets do not contain the same elements.");
        
        ++start1;
        }
    }