dsp_roots.hpp

// This file is part of DSP library containing useful reusable
// signal processing utility classes.
//
// Copyright (C) 2018 Duncan Crutchley
// Contact <dac1976github@outlook.com>
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published
// by the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License and GNU Lesser General Public License
// for more details.
//
// You should have received a copy of the GNU General Public License
// and GNU Lesser General Public License along with this program. If
// not, see <http://www.gnu.org/licenses/>.

/*!
 * \file dsp_roots.hpp
 * \brief File containing generic accurate definitions for sqrt(2) for any floating point type.
 */
#ifndef DSP_ROOTS_HPP
#define DSP_ROOTS_HPP

#include <type_traits>
#include <cmath>

/*! \brief dsp namespace */
namespace dsp
{

/*!
 * \brief Function to compute sqrt(2) for any floating point type.
 * \return Result represented as a floating point value of type T.
 *
 * This function only has computational cost when first called. All
 * subsequent calls simply return the static const result from
 * the first time the function was called.
 *
 * If called with anything other than a flaoting point type for T
 * then a static_assert will fire reporting an invalid type.
 */
template <typename FloatType> FloatType SqrtTwo()
{
    static_assert(std::is_floating_point<FloatType>::value, "invalid floating point type");
    static const auto result = std::sqrt(static_cast<FloatType>(2));
    return result;
}

/*!
 * \brief Function to compute 2sqrt(2) for any floating point type.
 * \return Result represented as a floating point value of type T.
 *
 * This function only has computational cost when first called. All
 * subsequent calls simply return the static const result from
 * the first time the function was called.
 *
 * If called with anything other than a flaoting point type for T
 * then a static_assert will fire reporting an invalid type.
 */
template <typename FloatType> FloatType TwoSqrtTwo()
{
    static const auto result = static_cast<FloatType>(2) * SqrtTwo<FloatType>();
    return result;
}

/*!
 * \brief Function to compute 1/sqrt(2) for any floating point type.
 * \return Result represented as a floating point value of type T.
 *
 * This function only has computational cost when first called. All
 * subsequent calls simply return the static const result from
 * the first time the function was called.
 *
 * If called with anything other than a flaoting point type for T
 * then a static_assert will fire reporting an invalid type.
 */
template <typename FloatType> FloatType OneOverSqrtTwo()
{
    static const auto result = static_cast<FloatType>(1) / SqrtTwo<FloatType>();
    return result;
}

/*!
 * \brief Function to compute 1/2sqrt(2) for any floating point type.
 * \return Result represented as a floating point value of type T.
 *
 * This function only has computational cost when first called. All
 * subsequent calls simply return the static const result from
 * the first time the function was called.
 *
 * If called with anything other than a flaoting point type for T
 * then a static_assert will fire reporting an invalid type.
 */
template <typename FloatType> FloatType OneOverTwoSqrtTwo()
{
    static const auto result = static_cast<FloatType>(1) / TwoSqrtTwo<FloatType>();
    return result;
}

} // namespace dsp

#endif // DSP_ROOTS_HPP