is_unitary.hpp

Go to the documentation of this file.

// SPDX-License-Identifier: BSD-2-Clause
 
#ifndef pRC_CORE_TENSOR_OPERATOR_FUNCTIONS_IS_UNITARY_H
#define pRC_CORE_TENSOR_OPERATOR_FUNCTIONS_IS_UNITARY_H
 
#include <prc/core/functors/adjoint.hpp>
#include <prc/core/functors/is_approx.hpp>
#include <prc/core/tensor/operator/functions/adjoint.hpp>
#include <prc/core/tensor/type_traits.hpp>
#include <prc/core/value/limits.hpp>
 
namespace pRC
{
    template<class X, class R = RemoveReference<X>, If<IsTensorish<R>> = 0,
        If<IsInvocable<Adjoint, X>> = 0,
        If<IsInvocable<IsApprox, ResultOf<Mul, ResultOf<Adjoint, X>, X>,
            ResultOf<Mul, ResultOf<Adjoint, X>, X>>> = 0,
        class TT = typename R::Value>
    static inline constexpr auto isUnitary(X &&a,
        TT const &tolerance = NumericLimits<TT>::tolerance())
    {
        using T = RemoveReference<decltype((adjoint(a) * a))>;
        return isApprox(adjoint(a) * a, identity<T>(), tolerance);
    }
}
#endif // pRC_CORE_TENSOR_OPERATOR_FUNCTIONS_IS_UNITARY_H