Indexing/Slicing of Matrices just works with indices which count from the start of the matrix:
https://community.jmp.com/t5/Uncharted/What-is-the-JSL-Matrix/m-p/33349
counting from the back or leaving the start or end open doesn't seem to work:
https://community.jmp.com/t5/Discussions/Collection-of-quot-funny-quot-JSL-newbie-questions/m-p/559081
my wish:
add the missing functionality such that indexing like this is also possible:
mat[1::-1];
mat[1::];
mat[::-1];
mat[::];
mat[::, x] is already possible as mat[0,x]
