NAME

       test, trial - symbolic arguments in variational expressions

DESCRIPTION

       These  classes  are  used for test and trial functions involved in variational formulations.  Variational
       formulations could be specified by expressions, in the spirit of c++ embeded languages.   A  variable  of
       the  test  type represents the formal argument (the test-function) in the definition of a linear form, as
       in:

           geo omega ("circle");
           space Xh (omega, "P1");
           test v(Xh);
           field lh = integrate (omega, 2*v);

       For a bilinear form, the test-function represents its second formal argument,  while  the  first  one  is
       designed by the trial type:

           trial u(Xh);
           test  v(Xh);
           form m = integrate (omega, u*v),
                a = integrate (omega, dot(grad(u),grad(v)));

       The  field_vf class is abble to represents either test or trial types: it could be used to formaly define
       a differential operator, as:

           D(u) = (grad(u)+trans(grad(u)))

rheolef-6.7                                        rheolef-6.7                                    test(2rheolef)