WCPS - NEW - support sort() operator

[Bang Pham Huu]

petascope needs to support sort() operator in WCPS. The doc for sort() operator in rasql is at ​file:///home/rasdaman/rasdaman_community/rasdaman/doc/main/_build/html/04_ql-guide.html#sort-operator

• The sort operator enables the user to sort an array along an axis of that array.
• The sorting is done by:
  • Slicing the array along that axis
  • Calculating a slice rank for each of the slices
  • Then rearranging the slices according to their ranks, in an ascending or descending order.

Proposed syntax in WCPS (based on rasql syntax):

SORT generalExp ALONG sortAxis [listingOrder] BY cellExp

where:

• generalExp is an MDD expression, for example: $c + 50
• sortAxis is an axis belonging to the coverage in generalExp, for example: Lat orLong or ansi
• listingOrder is ASC or DESC (default: ASC)
• cellExp is the ranking function, for example: $c[Long(30)] or $c[Lat:"CRS:1"(0)] or min($c[ansi("2015-05-01":"2016-07-02")])

NOTE: The sortAxis and other unspecified axes are translated to a rasql cellExp implicitly.

• For example: WCPS expression: SORT $c ALONG ansi BY min($c[Long(30:30)]) is translated to rasql expression: SORT c ALONG 0 AS i BY min_cells(c[i[0], 0:0, *:*]) (geo coordinate 30 of Long axis is translated to grid index 0).