Simplification: pattern matching

Author: cdrnet

src/Data.Text/MatrixMarketWriter.cs

@@ -127,8 +127,7 @@ public static void WriteMatrix<T>(TextWriter writer, Matrix<T> matrix) where T :
             var format = CreateValueFormatter<T>();
             var storage = matrix.Storage;
 
-            var sparse = storage as SparseCompressedRowMatrixStorage<T>;
-            if (sparse != null)
+            if (storage is SparseCompressedRowMatrixStorage<T> sparse)
             {
                 writer.WriteLine("%%MatrixMarket matrix coordinate {0} general", complex ? "complex" : "real");
                 writer.WriteLine("{0} {1} {2}", sparse.RowCount, sparse.ColumnCount, sparse.ValueCount);
@@ -144,8 +143,7 @@ public static void WriteMatrix<T>(TextWriter writer, Matrix<T> matrix) where T :
                 return;
             }
 
-            var diagonal = storage as DiagonalMatrixStorage<T>;
-            if (diagonal != null)
+            if (storage is DiagonalMatrixStorage<T> diagonal)
             {
                 writer.WriteLine("%%MatrixMarket matrix coordinate {0} general", complex ? "complex" : "real");
                 writer.WriteLine("{0} {1} {2}", diagonal.RowCount, diagonal.ColumnCount, diagonal.Data.Length);
@@ -157,8 +155,7 @@ public static void WriteMatrix<T>(TextWriter writer, Matrix<T> matrix) where T :
                 return;
             }
 
-            var dense = storage as DenseColumnMajorMatrixStorage<T>;
-            if (dense != null)
+            if (storage is DenseColumnMajorMatrixStorage<T> dense)
             {
                 writer.WriteLine("%%MatrixMarket matrix array {0} general", complex ? "complex" : "real");
                 writer.WriteLine("{0} {1}", dense.RowCount, dense.ColumnCount);
@@ -184,8 +181,7 @@ public static void WriteVector<T>(TextWriter writer, Vector<T> vector) where T :
             var format = CreateValueFormatter<T>();
             var storage = vector.Storage;
 
-            var sparse = storage as SparseVectorStorage<T>;
-            if (sparse != null)
+            if (storage is SparseVectorStorage<T> sparse)
             {
                 writer.WriteLine("%%MatrixMarket vector coordinate {0}", complex ? "complex" : "real");
                 writer.WriteLine("{0} {1}", sparse.Length, sparse.ValueCount);
@@ -197,8 +193,7 @@ public static void WriteVector<T>(TextWriter writer, Vector<T> vector) where T :
                 return;
             }
 
-            var dense = storage as DenseVectorStorage<T>;
-            if (dense != null)
+            if (storage is DenseVectorStorage<T> dense)
             {
                 writer.WriteLine("%%MatrixMarket vector array {0}", complex ? "complex" : "real");
                 writer.WriteLine("{0}", dense.Length);

src/Numerics.Tests/Random/RandomTests.cs

@@ -78,8 +78,7 @@ public void Sample()
             Assert.IsTrue(sum >= (N/2.0) - (.05*N));
             Assert.IsTrue(sum <= (N/2.0) + (.05*N));
 
-            var disposable = random as IDisposable;
-            if (disposable != null)
+            if (random is IDisposable disposable)
             {
                 disposable.Dispose();
             }
@@ -101,8 +100,7 @@ public void Boundaries()
                 Assert.IsTrue(next < j, string.Format("Value {0} is larger or equal to upper bound {1}", next, j));
             }
 
-            var disposable = random as IDisposable;
-            if (disposable != null)
+            if (random is IDisposable disposable)
             {
                 disposable.Dispose();
             }

src/Numerics/LinearAlgebra/Complex/Solvers/MILU0Preconditioner.cs

@@ -82,8 +82,7 @@ public MILU0Preconditioner(bool modified = true)
         /// instance of SparseCompressedRowMatrixStorage.</exception>
         public void Initialize(Matrix<Complex> matrix)
         {
-            var csr = matrix.Storage as SparseCompressedRowMatrixStorage<Complex>;
-            if (csr == null)
+            if (!(matrix.Storage is SparseCompressedRowMatrixStorage<Complex> csr))
             {
                 throw new ArgumentException("Matrix must be in sparse storage format", nameof(matrix));
             }

src/Numerics/LinearAlgebra/Complex/SparseMatrix.cs

@@ -768,10 +768,7 @@ protected override void DoAdd(Matrix<Complex> other, Matrix<Complex> result)
         /// <exception cref="ArgumentOutOfRangeException">If the two matrices don't have the same dimensions.</exception>
         protected override void DoSubtract(Matrix<Complex> other, Matrix<Complex> result)
         {
-            var sparseOther = other as SparseMatrix;
-            var sparseResult = result as SparseMatrix;
-
-            if (sparseOther == null || sparseResult == null)
+            if (!(other is SparseMatrix sparseOther) || !(result is SparseMatrix sparseResult))
             {
                 base.DoSubtract(other, result);
                 return;
@@ -886,9 +883,8 @@ protected override void DoMultiply(Complex scalar, Matrix<Complex> result)
         /// <param name="result">The result of the multiplication.</param>
         protected override void DoMultiply(Matrix<Complex> other, Matrix<Complex> result)
         {
-            var sparseOther = other as SparseMatrix;
             var sparseResult = result as SparseMatrix;
-            if (sparseOther != null && sparseResult != null)
+            if (other is SparseMatrix sparseOther && sparseResult != null)
             {
                 DoMultiplySparse(sparseOther, sparseResult);
                 return;

src/Numerics/LinearAlgebra/Complex32/Solvers/MILU0Preconditioner.cs

@@ -82,8 +82,7 @@ public MILU0Preconditioner(bool modified = true)
         /// instance of SparseCompressedRowMatrixStorage.</exception>
         public void Initialize(Matrix<Complex32> matrix)
         {
-            var csr = matrix.Storage as SparseCompressedRowMatrixStorage<Complex32>;
-            if (csr == null)
+            if (!(matrix.Storage is SparseCompressedRowMatrixStorage<Complex32> csr))
             {
                 throw new ArgumentException("Matrix must be in sparse storage format", nameof(matrix));
             }

src/Numerics/LinearAlgebra/Complex32/SparseMatrix.cs

@@ -884,9 +884,8 @@ protected override void DoMultiply(Complex32 scalar, Matrix<Complex32> result)
         /// <param name="result">The result of the multiplication.</param>
         protected override void DoMultiply(Matrix<Complex32> other, Matrix<Complex32> result)
         {
-            var sparseOther = other as SparseMatrix;
             var sparseResult = result as SparseMatrix;
-            if (sparseOther != null && sparseResult != null)
+            if (other is SparseMatrix sparseOther && sparseResult != null)
             {
                 DoMultiplySparse(sparseOther, sparseResult);
                 return;

src/Numerics/LinearAlgebra/Double/Solvers/MILU0Preconditioner.cs

@@ -80,8 +80,7 @@ public MILU0Preconditioner(bool modified = true)
         /// instance of SparseCompressedRowMatrixStorage.</exception>
         public void Initialize(Matrix<double> matrix)
         {
-            var csr = matrix.Storage as SparseCompressedRowMatrixStorage<double>;
-            if (csr == null)
+            if (!(matrix.Storage is SparseCompressedRowMatrixStorage<double> csr))
             {
                 throw new ArgumentException("Matrix must be in sparse storage format", nameof(matrix));
             }

src/Numerics/LinearAlgebra/Double/SparseMatrix.cs

@@ -884,9 +884,8 @@ protected override void DoMultiply(double scalar, Matrix<double> result)
         /// <param name="result">The result of the multiplication.</param>
         protected override void DoMultiply(Matrix<double> other, Matrix<double> result)
         {
-            var sparseOther = other as SparseMatrix;
             var sparseResult = result as SparseMatrix;
-            if (sparseOther != null && sparseResult != null)
+            if (other is SparseMatrix sparseOther && sparseResult != null)
             {
                 DoMultiplySparse(sparseOther, sparseResult);
                 return;

src/Numerics/LinearAlgebra/Single/Solvers/MILU0Preconditioner.cs

@@ -80,8 +80,7 @@ public MILU0Preconditioner(bool modified = true)
         /// instance of SparseCompressedRowMatrixStorage.</exception>
         public void Initialize(Matrix<float> matrix)
         {
-            var csr = matrix.Storage as SparseCompressedRowMatrixStorage<float>;
-            if (csr == null)
+            if (!(matrix.Storage is SparseCompressedRowMatrixStorage<float> csr))
             {
                 throw new ArgumentException("Matrix must be in sparse storage format", nameof(matrix));
             }

src/Numerics/LinearAlgebra/Single/SparseMatrix.cs

@@ -889,9 +889,8 @@ protected override void DoMultiply(float scalar, Matrix<float> result)
         /// <param name="result">The result of the multiplication.</param>
         protected override void DoMultiply(Matrix<float> other, Matrix<float> result)
         {
-            var sparseOther = other as SparseMatrix;
             var sparseResult = result as SparseMatrix;
-            if (sparseOther != null && sparseResult != null)
+            if (other is SparseMatrix sparseOther && sparseResult != null)
             {
                 DoMultiplySparse(sparseOther, sparseResult);
                 return;