Fix some typos

Eigen/src/Core/util/Constants.h

@@ -136,7 +136,7 @@ const unsigned int LinearAccessBit = 0x10;
   * Means the expression has a coeffRef() method, i.e. is writable as its individual coefficients are directly addressable.
   * This rules out read-only expressions.
   *
-  * Note that DirectAccessBit and LvalueBit are mutually orthogonal, as there are examples of expression having one but note
+  * Note that DirectAccessBit and LvalueBit are mutually orthogonal, as there are examples of expression having one but not
   * the other:
   *   \li writable expressions that don't have a very simple memory layout as a strided array, have LvalueBit but not DirectAccessBit
   *   \li Map-to-const expressions, for example Map<const Matrix>, have DirectAccessBit but not LvalueBit

doc/CustomizingEigen_Plugins.dox

@@ -59,7 +59,7 @@ operator+(const Scalar& scalar, const MatrixBase<Derived>& mat)
 { return CwiseBinaryOp<internal::scalar_sum_op<Scalar>, const ConstantReturnType, Derived>(Constant(rows(),cols(),scalar), mat.derived()); }
 \endcode
 
-Then one can the following declaration in the config.h or whatever prerequisites header file of his project:
+Then one can add the following declaration in the config.h or whatever prerequisites header file of his project:
 \code
 #define EIGEN_MATRIXBASE_PLUGIN "MatrixBaseAddons.h"
 \endcode

doc/FunctionsTakingEigenTypes.dox

@@ -126,7 +126,7 @@ and contrary to what one might think at first, this implementation is fine unles
 MatrixXf x,y,z;
 MatrixXf C = cov(x,y+z);
 \endcode
-In this special case, the example is fine and will be working because both parameters are declared as \e const references. The compiler creates a temporary and evaluates the expression x+z into this temporary. Once the function is processed, the temporary is released and the result is assigned to C.
+In this special case, the example is fine and will be working because both parameters are declared as \e const references. The compiler creates a temporary and evaluates the expression y+z into this temporary. Once the function is processed, the temporary is released and the result is assigned to C.
 
 \b Note: Functions taking \e const references to Matrix (or Array) can process expressions at the cost of temporaries.
 

doc/SparseQuickReference.dox

@@ -153,7 +153,7 @@ It is easy to perform arithmetic operations on sparse matrices provided that the
 \code 
 perm.indices();      // Reference to the vector of indices
 sm1.twistedBy(perm); // Permute rows and columns
-sm2 = sm1 * perm;    // Permute the columns
+sm2 = sm1 * perm;    // Permute the rows
 sm2 = perm * sm1;    // Permute the columns
 \endcode 
 </td>

doc/examples/matrixfree_cg.cpp

@@ -9,7 +9,7 @@ using Eigen::SparseMatrix;
 
 namespace Eigen {
 namespace internal {
-  // MatrixReplacement looks-like a SparseMatrix, so let's inherits its traits:
+  // MatrixReplacement looks-like a SparseMatrix, so let's inherit its traits:
   template<>
   struct traits<MatrixReplacement> :  public Eigen::internal::traits<Eigen::SparseMatrix<double> >
   {};