Tally

Z←≢R returns an integer scalar identical to ⍬⍴(⍴R),1.

R is an arbitrary array.

Z is an integer scalar whose value is the number of items along the first coordinate of R.

For example,

      ≢⍬
0
      ≢23
1
      ≢,23
1
      ≢2 3 4⍴5 6
2