@Adám The Wiki page on Tatin includes a reference to Dyalog 19.0 that I'm guessing is outdated, but I don't know what the current status is. Mind updating it?

@Marshall Thanks, but I think that's still accurate.

how to multiply a matrix and vector?

@elliptic00 What result do you expect?

   m
 0 1
¯1 1
      v
2
0
      m × v
LENGTH ERROR: Mismatched left and right argument shapes
      m×v
       ∧

a vector

I very much doubt v is a vector.

What is ⍴v?

That'd be a 2-row, 1-column matrix.

Do you by any chance expect the result

 0
¯2

?

yes

m+.×v then.

ok,

thx

what if the v is just array, not a matrix?

column array?

@elliptic00 That's impossible; a column array is a matrix.

However, if v is a vector, the corresponding code is m+.×v

In general, if some APL code is well-written, the same code works no matter what ranks the involved arrays have.

+.× so it is like just generalization dot product of matrix and vector , vector and vector

matrix and matrix