NB. J Phrases Section 2B. Rank

m0=: +/         NB. sum (column sums of a matrix)
m1=: +/"1       NB. sum vectors (row sums of a matrix)
d2=: *"0 _      NB. outer product; same as */
m3=: +/@(*"1 _) NB. inner product; same as +/ .*
