[Jasper Z]

Dear all,

I am looking at KinematicParcelTrackingDataI.H in the lagrangian library, but I don't know what the 'cloud' in TrackCloudType& cloud stands for? In the following codes:

template<class ParcelType>
template<class TrackCloudType>
inline Foam::KinematicParcel<ParcelType>::trackingData::trackingData
(
    const TrackCloudType& cloud,
    trackPart part
)
:
    ParcelType::trackingData(cloud),
    rhoInterp_
    (
        interpolation<scalar>::New
        (
            cloud.solution().interpolationSchemes(),
            cloud.rho()
        )
    ),

cloud calls the functions solution(). and rho(), but when I change them to a random letter, e.g., change rho() to a(), and wmake can still compile the library. I want to know why does this happen？ What is the 'cloud' here?