HELP ARRAY_TRANSPOSE                            David Young, March 2001
                                                revised Oct 2001


LIB *array_transpose provides a procedure for obtaining the transpose of
a region of a two-dimensional array.

array_transpose(_____arrin, ________regionin, ______arrout) -> ______arrout
        The first argument, _____arrin, must be a 2-D array. Arrays of packed
        floats (as returned by *newsfloatarray) and packed bytes (as
        returned by *newbytearray) are handled more efficiently than
        other types, provided that they are arrayed "by row".

        ________regionin may be <false>, in which case data is taken from the
        whole of _____arrin. Otherwise, ________regionin must  specify, in
        *boundslist  form, the region of _____array from which  data are to
        be taken.

        Suppose ________regionin (or the boundslist of _____arrin if ________regionin is
        false) has the form [x0 x1 y0 y1]. If ______arrout is an array on
        entry, it must contain the region [y0 y1 x0 x1], and data is
        written to this region. If _____arrin is one of the special types of
        array mentioned above, then for efficiency ______arrout should be the
        same type. ______arrout and _____arrin may not be the same array or have
        the same arrayvector.

        If ______arrout is <false> on entry, a new array of the same type as
        _____arrin and with bounds [y0 y1 x0 x1] is created and returned.

        If ______arrout is not an array and not <false> on entry, a recyclable
        array, as produced by oldanyarray (see *oldarray) is created and
        returned, using ______arrout as the tag. This can reduce garbage
        creation when temporary arrays are used in a procedure. The
        output array has the same type as _____arrin and the bounds [y0 y1 x0
        x1].

        On exit from the procedure, ______arrout(_y, _x) = _____arrin(_x, _y) for all _x
        and _y such that __x0 <= _x <= __x1 and __y0 <= _y <= __y1.


--- _______________________________$popvision/help/array_transpose
--- _________Copyright __________University __of ______Sussex _____2001. ___All ______rights _________reserved.