(e) The indicial expressions

The indicial expressions referred to above are linear functions of the cell-location-coordinate indices, IX, IY and IZ; and the coefficients in the linear functions involve the total numbers of cells in these three coordinate directions, namely NX, NY and NZ.

The indicial expressions are:

for XWV's, IX
for YWV's, IY
for ZWV's, IZ
for SWV's and for FFV's other than WSV's, IY+NY*(IX-1)
for WSV's, IY+NY*(IX-1)+NX*NY*(IZ-1)
for PWV's, (IY-IYF+1)+(IYL-IYF+1)*(IX-IXF)+(IYL-IYF+1)* (IXL-IXF+1)*(IZ-IZF)

These formulae express the fact that, on a slab of fixed IZ, the cells are ordered as indicated below:

IY increasing


    ^
    |    NY      2*NY    3*NY    .........   (NX-1)*NY    NX*NY
    |    NY-1    2*NY-1                                   NX*NY-1
    |    NY-2    .                                           .
    |    .       .                                           .
    |    .       .                                           .
    |    .       .                                           .
    |    4       .                                           .
    |    3       NY+3                                        .
    |    2       NY+2                                        .
    |    1       NY+1    2*NY+1  ......................   (NX-1)*NY+1
    |
    -------------------------------------------------> IX increasing

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