    // Copyright (C) 2013  Davis E. King (davis@dlib.net)
    // License: Boost Software License   See LICENSE.txt for the full license.
    #undef DLIB_FFt_ABSTRACT_Hh_
    #ifdef DLIB_FFt_ABSTRACT_Hh_

    #include "matrix_abstract.h"
    #include "../algs.h"

    namespace dlib
    {

    // ----------------------------------------------------------------------------------------

        bool is_power_of_two (
            const unsigned long& value
        );
        /*!
            ensures
                - returns true if value contains a power of two and false otherwise.  As a
                  special case, we also consider 0 to be a power of two.
        !*/

    // ----------------------------------------------------------------------------------------

        template <typename EXP>
        typename EXP::matrix_type fft (
            const matrix_exp<EXP>& data
        );
        /*!
            requires
                - data contains elements of type std::complex<>
                - is_power_of_two(data.nr()) == true
                - is_power_of_two(data.nc()) == true
            ensures
                - Computes the 1 or 2 dimensional discrete Fourier transform of the given data
                  matrix and returns it.  In particular, we return a matrix D such that:
                    - D.nr() == data.nr()
                    - D.nc() == data.nc()
                    - D(0,0) == the DC term of the Fourier transform.
                    - starting with D(0,0), D contains progressively higher frequency components
                      of the input data.
                    - ifft(D) == D
        !*/

    // ----------------------------------------------------------------------------------------

        template <typename EXP>
        typename EXP::matrix_type ifft (
            const matrix_exp<EXP>& data
        );
        /*!
            requires
                - data contains elements of type std::complex<>
                - is_power_of_two(data.nr()) == true
                - is_power_of_two(data.nc()) == true
            ensures
                - Computes the 1 or 2 dimensional inverse discrete Fourier transform of the
                  given data vector and returns it.  In particular, we return a matrix D such
                  that:
                    - D.nr() == data.nr()
                    - D.nc() == data.nc()
                    - fft(D) == data
        !*/

    // ----------------------------------------------------------------------------------------

        template <
            typename T,
            long NR,
            long NC,
            typename MM,
            typename L
            >
        void fft_inplace (
            matrix<std::complex<T>,NR,NC,MM,L>& data
        );
        /*!
            requires
                - data contains elements of type std::complex<>
                - is_power_of_two(data.nr()) == true
                - is_power_of_two(data.nc()) == true
            ensures
                - This function is identical to fft() except that it does the FFT in-place.
                  That is, after this function executes we will have:
                    - #data == fft(data)
        !*/

    // ----------------------------------------------------------------------------------------

        template <
            typename T,
            long NR,
            long NC,
            typename MM,
            typename L
            >
        void ifft_inplace (
            matrix<std::complex<T>,NR,NC,MM,L>& data
        );
        /*!
            requires
                - data contains elements of type std::complex<>
                - is_power_of_two(data.nr()) == true
                - is_power_of_two(data.nc()) == true
            ensures
                - This function is identical to ifft() except that it does the inverse FFT
                  in-place.  That is, after this function executes we will have:
                    - #data == ifft(data)*data.size()
                    - Note that the output needs to be divided by data.size() to complete the
                      inverse transformation.
        !*/

    // ----------------------------------------------------------------------------------------

    }

    #endif // DLIB_FFt_ABSTRACT_Hh_