Representation.h

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#pragma once
 
#include "to_univariate_polynomial.h"
 
#include "../MultivariatePolynomial.h"
#include "../UnivariatePolynomial.h"
 
namespace carl {
 
/**
 * Switches the main variable using a purely syntactical restructuring.
 * The resulting polynomial will be algebraicly identical, but have the given variable as its main variable.
 * @param p The polynomial.
 * @param newVar New main variable.
 * @return Restructured polynomial.
 */
template<typename Coeff>
UnivariatePolynomial<MultivariatePolynomial<typename UnderlyingNumberType<Coeff>::type>> switch_main_variable(const UnivariatePolynomial<Coeff>& p, Variable newVar) {
    assert(p.is_consistent());
    using MP = MultivariatePolynomial<typename UnderlyingNumberType<Coeff>::type>;
    return to_univariate_polynomial(MP(p), newVar);
}
 
/**
 * Replaces the main variable in a polynomial.
 * @param p The polynomial.
 * @param newVar New main variable.
 * @return New polynomial.
 */
template<typename Coeff>
UnivariatePolynomial<Coeff> replace_main_variable(const UnivariatePolynomial<Coeff>& p, Variable newVar) {
    if constexpr (carl::is_number_type<Coeff>::value) {
        return UnivariatePolynomial<Coeff>(newVar, p.coefficients());
    } else {
        using MP = MultivariatePolynomial<typename UnderlyingNumberType<Coeff>::type>;
        return to_univariate_polynomial(substitute(MP(p), p.main_var(), MP(newVar)), newVar);
    }
}
 
template<typename C, typename O, typename P>
MultivariatePolynomial<C,O,P> switch_variable(const MultivariatePolynomial<C,O,P>& p, Variable old_var, Variable new_var) {
    return substitute(p, old_var, MultivariatePolynomial<C,O,P>(new_var));
}
 
}