4.4. SIDL definition of the Midpoint component

4.4. SIDL definition of the Midpoint component
	Chapter 4. Creating a Component from an Existing Library

We will write a SIDL-based component that implements the port defined in previous steps and calls the integrate_mp method implemented in the legacy code described in Section 4.1, “The legacy Fortran integrator” to integrate a function, using function components that implement the function.FunctionPort port described in The integrator.IntegratorPort definition.

Edit the file, student-src/components/sidl/integrators.sidl to define the class for the new integrator component, integrators.Midpoint:

package integrators version 1.0 {

  // The following components implement all methods of the 
  // integrator.IntegratorPort and gov.cca.Component interfaces.
  // Since they use the SIDL 'implements-all' keyword, the 
  // methods do not need to (but optionally can) be listed explicitly.

  class Midpoint implements-all integrator.IntegratorPort, 
                                gov.cca.Component
  {
  }

  class MonteCarlo implements-all integrator.IntegratorPort, 
                                  gov.cca.Component
                                  gov.cca.ComponentRelease
  {
    // integrator.IntegratorPort methods:
    double integrate(in double lowBound, in double upBound, 
                     in int count);

    // gov.cca.Component methods:
    void setServices(in gov.cca.Services services) 
                    throws gov.cca.CCAException;

    // gov.cca.ComponentRelease methods:
    void releaseServices(in gov.cca.Services services) 
                        throws gov.cca.CCAException;
  }
}

Note that the Midpoint class, unlike the MonteCarlo class does not implement the gov.cca.ComponentRelease interface, which is optional.

Edit the file student-src/components/MakeIncl.components to add a new component description in the COMPONENTS variable, which contains the list of components in this directory. Each value consists of the fully-qualified name of the component (including packages), to which we append "-language", where language is one of c, c++, or f90. In this case, the name is integrators.Midpoint, and the language is f90, so you need to add integrators.Midpoint-f90. The updated value of COMPONENTS should look like something like this:
```
COMPONENTS = functions.PiFunction-c++ \
        integrators.MonteCarlo-f90 randomgens.RandNumGenerator-c++ \
        drivers.F90Driver-f90 drivers.CXXDriver-c++  \
        integrators.Midpoint-f90
```
Note the backslash (“\”) that has to be added in order to extend the entry to the next line.
In the student-src/components directory, run make .repository. This will generate the XML representation of the integrator.Midpoint SIDL class and store it in the student-src/xml_repository directory.
In the student-src/components directory, run make .integrators.Midpoint-f90. This will generate Fortran 90 server code for the integrators.Midpoint component class.