// coefficients in previous examples, but there is another possibility in
// the library, namely a base class that describes tensor valued
// functions. This is more convenient than overriding Function::value() with
- // a method that knows about multiple function components: at the end of the
+ // a method that knows about multiple function components: At the end of the
// day we need a Tensor, so we may as well just use a class that returns a
// Tensor.
template <int dim>
{
public:
virtual Tensor<1, dim> value(const Point<dim> &p) const override;
-
- // In previous examples, we have used assertions that throw exceptions in
- // several places. However, we have never seen how such exceptions are
- // declared. This can be done as follows:
- DeclException2(ExcDimensionMismatch,
- unsigned int,
- unsigned int,
- << "The vector has size " << arg1 << " but should have "
- << arg2 << " elements.");
- // The syntax may look a little strange, but is reasonable. The format is
- // basically as follows: use the name of one of the macros
- // <code>DeclExceptionN</code>, where <code>N</code> denotes the number of
- // additional parameters which the exception object shall take. In this
- // case, as we want to throw the exception when the sizes of two vectors
- // differ, we need two arguments, so we use
- // <code>DeclException2</code>. The first parameter then describes the
- // name of the exception, while the following declare the data types of
- // the parameters. The last argument is a sequence of output directives
- // that will be piped into the <code>std::cerr</code> object, thus the
- // strange format with the leading <code>@<@<</code> operator and the
- // like. Note that we can access the parameters which are passed to the
- // exception upon construction (i.e. within the <code>Assert</code> call)
- // by using the names <code>arg1</code> through <code>argN</code>, where
- // <code>N</code> is the number of arguments as defined by the use of the
- // respective macro <code>DeclExceptionN</code>.
- //
- // To learn how the preprocessor expands this macro into actual code,
- // please refer to the documentation of the exception classes. In brief,
- // this macro call declares and defines a class
- // <code>ExcDimensionMismatch</code> inheriting from ExceptionBase which
- // implements all necessary error output functions.
- //
- // @note This exception is similarly used inside the
- // <code>AssertDimension</code> macro, which is a handy wrapper to the
- // check the dimensions of two given objects.
};
- // The following two functions implement the interface described above. The
- // first simply implements the function as described in the introduction,
- // while the second uses the same trick to avoid calling a virtual function
- // as has already been introduced in the previous example program. Note the
- // check for the right sizes of the arguments in the second function, which
- // should always be present in such functions; it is our experience that
- // many if not most programming errors result from incorrectly initialized
- // arrays, incompatible parameters to functions and the like; using
- // assertion as in this case can eliminate many of these problems.
+
template <int dim>
Tensor<1, dim> AdvectionField<dim>::value(const Point<dim> &p) const
{
// the result into its final location, we do not need a copy-local-to-global
// function and will instead give the WorkStream::run() function an empty
// function object -- the equivalent to a NULL function pointer.
+ //
+ // There is one more part to this class.
+ // In previous examples, we have used assertions that throw exceptions in
+ // several places (see, for example, step-5 and step-8). However, you have
+ // never seen how such exceptions are declared. The code below shows how
+ // to do that, using the `DeclException2` macro.
+ //
+ // The syntax may look a little strange, but is reasonable. The format is
+ // basically as follows: Use the name of one of the macros
+ // <code>DeclExceptionN</code>, where <code>N</code> denotes the number of
+ // additional parameters which the exception object should take. In this
+ // case, as we want to throw the exception when the sizes of two vectors
+ // differ, we need two arguments, so we use
+ // <code>DeclException2</code>. The first parameter then describes the
+ // name of the exception, while the following declare the data types of
+ // the parameters. The last argument is a sequence of output directives
+ // that will be piped into the <code>std::cerr</code> object, thus the
+ // strange format with the leading `<<` operator and the
+ // like. Note that we can access the parameters which are passed to the
+ // exception upon construction (i.e. within the <code>Assert</code> call)
+ // by using the names <code>arg1</code> through <code>argN</code>, where
+ // <code>N</code> is the number of arguments as defined by the use of the
+ // respective macro <code>DeclExceptionN</code>.
+ //
+ // To learn how the preprocessor expands this macro into actual code,
+ // please refer to the documentation of the exception classes. In brief,
+ // this macro call declares and defines a class
+ // <code>ExcDimensionMismatch</code> inheriting from ExceptionBase which
+ // implements all necessary error output functions.
+ //
+ // @note This exception we declare here is similar to the used inside the
+ // <code>AssertDimension</code> macro, which is a handy wrapper for
+ // checking that the dimensions of two given objects are equal, and that
+ // you have already seen in step-8.
+
class GradientEstimation
{
public:
// other function, but there is a bit of setup at the top.
//
// Before starting with the work, we check that the vector into
- // which the results are written has the right size. Programming
+ // which the results are written has the right size, using the `Assert`
+ // macro and the exception class we declared above. Programming
// mistakes in which one forgets to size arguments correctly at the
// calling site are quite common. Because the resulting damage from
// not catching such errors is often subtle (e.g., corruption of
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