Custom sort?

[Albert Chan]

(01-20-2019 11:38 PM)Didier Lachieze Wrote:  In CAS :
sort({{1,2},{2,2.5},{3,1.5}},(x,y)->when(x[2] = y[2],x[1]>y[1],x[2]>y[2]))
returns:
{{2,2.5},{1,2},{3,1.5}}

Another way is Schwartian transformed sort.
For above case, assuming 1-based indexing, in X-Cas:

m := [[1,2], [2,2.5], [3,1.5]]
reverse(swapcol(sort(swapcol(m, 1,2)), 1,2)) --> [[2,2.5], [1,2], [3,1.5]]