Provided by: librheolef-dev_5.93-2_amd64 #### NAME

```       riesz_representer - integrate a function by using quadrature formulae

```

#### DESCRIPTION

```        The function riesz_representer implements the
approximation of an integral by using quadrature formulae.
This is an expreimental implementation: please do not use
yet for practical usage.

```

#### SYNOPSYS

```        template <class Function>
field riesz_representer (const space& Vh, const Function& f);

template <class Function>
field  riesz_representer  (const  space&  Vh,  const  Function& f, quadrature_option_type
qopt);

```

#### EXAMPLE

```        The following code compute the Riesz representant, denoted
by mfh of f(x), and the integral of f over the domain omega:

Float f(const point& x);
...
space Vh (omega_h, "P1");
field mfh = riesz_representer(Vh, f);
Float int_f = dot(mfh, field(Vh,1.0));

The Riesz representer is the mfh vector of values:

mfh(i) = integrate f(x) phi_i(x) dx

where phi_i is the i-th basis function in Vh
and the integral is evaluated by using a quadrature formulae.
By default the quadrature formule is the Gauss one with
the order equal to the polynomial order of Vh.
Alternative quadrature formulae and order is available
by passing an optional variable to riesz_representer.

```

#### IMPLEMENTATION

```       template <class Function>
field
riesz_representer (
const space& Vh,
const Function& f,