Content.h

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#pragma once
 
#include "../MultivariatePolynomial.h"
#include "../UnivariatePolynomial.h"
 
namespace carl {
    template<typename Coeff>
    Coeff content(const UnivariatePolynomial<Coeff>& p);
}
 
#include "GCD.h"
 
namespace  carl {
 
/**
 * The content of a polynomial is the gcd of the coefficients of the normal part of a polynomial.
 * The content of zero is zero.
 * @see @cite GCL92, page 53, definition 2.18
 * @return The content of the polynomial.
 */
template<typename Coeff>
Coeff content(const UnivariatePolynomial<Coeff>& p) {
    if (is_zero(p)) {
        // By definition
        return Coeff(0);
    }
    assert(p.is_normal());
    if constexpr (is_field_type<Coeff>::value) {
        // For fields, content(p) = 1
        return Coeff(1);
    }
    auto it = p.coefficients().rbegin();
    Coeff gcd = *it;
    for (++it; it != p.coefficients().rend(); ++it) {
        if (is_one(gcd)) {
            break;
        }
        if (is_zero(*it)) {
            continue;
        }
        gcd = carl::gcd(gcd, *it);
    }
    return gcd;
}
 
}