Fast way to update grids

[Alan T. Bowler [SDG]]

In article <2212 at geac.UUCP> daveb at geac.UUCP (David Collier-Brown) writes:
>  As
>the white book is written to allow edge-vector addressing, and at
>least one pcc-based compiler uses it, this turns out to be
>compiler-dependent.  
>  As it happens, the Waterloo (GCOS) C compiler uses edge-vectors, but
>also (if memory serves) keeps the pointed-at data contiguous to
>allow such assumptions to work nevertheless.  Something of a ``best
>of both worlds'' effect, at no extra cost to the program/programmer.

Sorry Dave, but that is just not true.  You get edge vectors only
if you declare the structure as having edgevectors.  If you declare
a multidimensional array you get the conventional contiguous chunk
of memory and addressing polynomials to access it.  Are you sure
you aren't getting confused with B (and BCPL) where edgevectors
was the only choice?

                           Alan Bowler
                           Product Support
                           Software Development Group
                           University of Waterloo