HELP ARRAY_WRAP                                 David Young
                                                revised February 2000

LIB * ARRAY_WRAP provides a procedure to copy an array or region of an
array to another region assuming that the data are periodic on the input
region.

array_wrap(_____arrin, _____regin, ______arrout, ______regout) -> ______arrout
        _____arrin is the input array. Arrays of packed byte or float data
        (as created by *newbytearray and *newsfloatarray) are handled
        most efficiently.

        _____regin is the input region, given as a *boundslist type list.
        Alternatively, it may be <false>, in which case the boundslist
        of _____arrin is used. _____regin need not be wholly (or partly) within
        _____arrin.

        ______arrout is the output array. If <false> on entry, an array of the
        same type as _____arrin and with boundslist given by ______regout is
        created and returned.

        ______regout is a boundslist-type specification of the output region
        into which data are written. If <false>, ______arrout must be an
        array, and its boundslist will be used as ______regout. If both ______arrout
        and ______regout are given, then ______regout must lie wholly within the
        bounds of ______arrout.

        The result ______arrout will be set such that

                ______arrout(_x, _y, ...) = _____arrin(_a, _b, ...)

        if _x mod _N = _a mod _N, _y mod _M = _b mod _M etc., where _N =
        _____regin(2)-_____regin(1)+1, _M = _____regin(4)-_____regin(3)+1 etc., for all
        elements (_x, _y, ...) within ______regout, and for which (_a, _b, ...)
        lies within _____regin and within the boundslist of _____arrin. If this
        last condition does not hold, then ______arrout(_x, _y, ...) is set to
        zero.

        Note that this means that the input region, not the whole of the
        input array, sets the periodicity and is the unit which tiles
        the output array. The input array is not taken to be periodic,
        so if the input region goes outside its bounds, the missing data
        is set to zero and not taken from another part of the input
        array.


--- __________________________$popvision/help/array_wrap
--- _________Copyright __________University __of ______Sussex _____2000. ___All ______rights _________reserved.