Sorting a Matrix by column1 then column2

[rafael.guerra]

The following seems to work with a minus sign trick:

M =[
19 25
23 24
23 20
20 30]

sortslices(M,dims=1,by=x->(x[1],-x[2]),rev=true)

4×2 Matrix{Int64}:
 23  20
 23  24
 20  30
 19  25