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namespace MathNet.Numerics.LinearAlgebra.Generic.Factorization
{
    using System;
    using System.Numerics;
    using Generic;

    /// <summary>
    /// Extension methods which return factorizations for the various matrix classes.
    /// </summary>
    public static class ExtensionMethods
    {
        /// <summary>
        /// Computes the Cholesky decomposition for a matrix.
        /// </summary>
        /// <param name="matrix">The matrix to factor.</param>
        /// <returns>The Cholesky decomposition object.</returns>
        /// <typeparam name="T">Supported data types are double, single, <see cref="Complex"/>, and <see cref="Complex32"/>.</typeparam>
        public static Cholesky<T> Cholesky<T>(this Matrix<T> matrix) where T : struct, IEquatable<T>, IFormattable
        {
            return Factorization.Cholesky<T>.Create(matrix);
        }

        /// <summary>
        /// Computes the LU decomposition for a matrix.
        /// </summary>
        /// <param name="matrix">The matrix to factor.</param>
        /// <returns>The LU decomposition object.</returns>
        /// <typeparam name="T">Supported data types are double, single, <see cref="Complex"/>, and <see cref="Complex32"/>.</typeparam>
        public static LU<T> LU<T>(this Matrix<T> matrix) where T : struct, IEquatable<T>, IFormattable
        {
            return Factorization.LU<T>.Create(matrix);
        }

        /// <summary>
        /// Computes the QR decomposition for a matrix.
        /// </summary>
        /// <param name="matrix">The matrix to factor.</param>
        /// <returns>The QR decomposition object.</returns>
        /// <typeparam name="T">Supported data types are double, single, <see cref="Complex"/>, and <see cref="Complex32"/>.</typeparam>
        public static QR<T> QR<T>(this Matrix<T> matrix) where T : struct, IEquatable<T>, IFormattable
        {
            return Factorization.QR<T>.Create(matrix);
        }

        /// <summary>
        /// Computes the QR decomposition for a matrix using Modified Gram-Schmidt Orthogonalization.
        /// </summary>
        /// <param name="matrix">The matrix to factor.</param>
        /// <returns>The QR decomposition object.</returns>
        /// <typeparam name="T">Supported data types are double, single, <see cref="Complex"/>, and <see cref="Complex32"/>.</typeparam>
        public static QR<T> GramSchmidt<T>(this Matrix<T> matrix) where T : struct, IEquatable<T>, IFormattable
        {
            if (typeof(T) == typeof(double))
            {
                return new LinearAlgebra.Double.Factorization.GramSchmidt(matrix as Matrix<double>) as QR<T>;
            }

            if (typeof(T) == typeof(float))
            {
                return new LinearAlgebra.Single.Factorization.GramSchmidt(matrix as Matrix<float>) as QR<T>;
            }

            if (typeof(T) == typeof(Complex))
            {
                return new LinearAlgebra.Complex.Factorization.GramSchmidt(matrix as Matrix<Complex>) as QR<T>;
            }

            throw new NotImplementedException();
        }

        /// <summary>
        /// Computes the SVD decomposition for a matrix.
        /// </summary>
        /// <param name="matrix">The matrix to factor.</param>
        /// <param name="computeVectors">Compute the singular U and VT vectors or not.</param>
        /// <returns>The QR decomposition object.</returns>
        /// <typeparam name="T">Supported data types are double, single, <see cref="Complex"/>, and <see cref="Complex32"/>.</typeparam>
        public static Svd<T> Svd<T>(this Matrix<T> matrix, bool computeVectors) where T : struct, IEquatable<T>, IFormattable
        {
            return Factorization.Svd<T>.Create(matrix, computeVectors);
        }
    }
}