GCD_Monomial.cpp

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#include "GCD_Monomial.h"
 
#include "../MonomialPool.h"
 
namespace carl {
 
Monomial::Arg gcd(const Monomial::Arg& lhs, const Monomial::Arg& rhs) {
    if(!lhs && !rhs) return nullptr;
    if(!lhs) return rhs;
    if(!rhs) return lhs;
 
    CARL_LOG_FUNC("carl.core.monomial", lhs << ", " << rhs);
    assert(lhs->is_consistent());
    assert(rhs->is_consistent());
 
    Monomial::Content newExps;
    std::size_t expsum = 0;
    // Linear, as we expect small monomials.
    auto itright = rhs->begin();
    auto leftEnd = lhs->end();
    auto rightEnd = rhs->end();
    for(auto itleft = lhs->begin(); (itleft != leftEnd && itright != rightEnd);)
    {
        // Variable is present in both monomials.
        if(itleft->first == itright->first)
        {
            std::size_t newExp = std::min(itleft->second, itright->second);
            newExps.emplace_back(itleft->first, newExp);
            expsum += newExp;
            ++itright;
            ++itleft;
        }
        else if(itleft->first < itright->first) 
        {
            ++itleft;
        }
        else
        {
            assert(itleft->first > itright->first);
            ++itright;
        }
    }
        // Insert remaining part
    std::shared_ptr<const Monomial> result;
    if (!newExps.empty()) {
        result = createMonomial(std::move(newExps), expsum);
    }
    CARL_LOG_TRACE("carl.core.monomial", "Result: " << result);
    return result;
}
 
}