Should functions take grids or arrays as arguments

[brryan]

Uncertain how to decide between grid and array types for function arguments. Consider for example a function that transforms a four-vector in the coordinate frame vCoord to the tetrad frame vTetrad; should this function be

void fluidElement::coordToTetrad(const array vCoord[NDIM], array vTetrad[NDIM])

or

void fluidElement::coordToTetrad(const grid &vCoord, grid &vTetrad)

?