[ecles]

Hello!

I have been trying to become acquainted with OpenFOAM code. Nonetheless I got stuck in one thing.

In gaussLaplacianScheme.C, we have the following line of code in fvmLaplacian routine:

tmp<fvMatrix<Type>> tfvm = fvmLaplacianUncorrected
(
SfGammaSn,
this->tsnGradScheme_().deltaCoeffs(vf),
vf
);

The object of the second parameter passed should belong to a surfaceScalarField class:

template<class Type, class GType>
tmp<fvMatrix<Type>>
gaussLaplacianScheme<Type, GType>::fvmLaplacianUncorrected
(
const surfaceScalarField& gammaMagSf,
const surfaceScalarField& deltaCoeffs,
const GeometricField<Type, fvPatchField, volMesh>& vf
)

Nonetheless, deltaCoeffs(vf), a pure virtual function declared in snGradScheme.H, is set to return a tmp pointer.

virtual tmp<surfaceScalarField> deltaCoeffs
(
const GeometricField<Type, fvPatchField, volMesh>&
) const = 0;


Should it not be returned as a surfaceScalarField object? What am I missing here? Is there any implicit conversion taking place?

Thank you!

[deepsterblue]

The GeometricField class (from which surfaceScalarField is defined) has a constructor that operates on a tmp object. The tmp class also has a const dereference operator overload, which implicitly converts a tmp object to a const reference (check tmp.H). All of this allows tmp objects to be implicitly convertible to the underlying GeometricField, while including reference counting capabilities.

[ecles]

Just to be sure I understood, is the implicit conversion implemented in this routine?

template<class T>
inline Foam::tmp<T>::operator const T&() const
{
return operator()();
}

[deepsterblue]

Yup - that's the one.