[bug #48564] Octave does not accept "1 / ND array", "mrdivide (1, ND array)", "mldivide (ND array, 1)"

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Follow-up Comment #16, bug #48564 (group octave):

ok, trying again

mrdivide:


x = B/A solves the system of linear equations x*A = B for x. The matrices A
and B must contain the same number of columns. MATLAB® displays a warning
message if A is badly scaled or nearly singular, but performs the calculation
regardless.

If A is a scalar, then B/A is equivalent to B./A.

If A is a square n-by-n matrix and B is a matrix with n columns, then x = B/A
is a solution to the equation x*A = B, if it exists.

If A is a rectangular m-by-n matrix with m ~= n, and B is a matrix with n
columns, then x = B/A returns a least-squares solution of the system of
equations x*A = B.


defined behavior only address behavior for A being 2D.  for any 2D A (not just
square), you get an attempt to solve B/A which will run into nonconformant
dimension errors.  so needs to apply to any 2D A.

if ndim > 3, it reverts to elementwise division, but this is undocumeted. 

and if any of the dims are empty, it seems a bit odd:

I'm guessing it leads with an 'if ismatrix do matrixsolve else elementwise
division' check.

see:

matlab 2025a:

>> 9 / rand(1,3)
Error using  / 
Matrix dimensions must agree.
 
>> 9 / rand(3,1)

ans =

         0         0   12.0855

>> 9 / rand(2,2)
Error using  / 
Matrix dimensions must agree.
 
>> 9 / rand(2,4)
Error using  / 
Matrix dimensions must agree.
 
>> 9 / rand(4,2)
Error using  / 
Matrix dimensions must agree.
 
>> 9 / rand(3)
Error using  / 
Matrix dimensions must agree.
 
>> 9 / rand(3,2,2)

ans(:,:,1) =

   19.1114   46.2097
   39.0476   39.8368
   10.6596   52.7216


ans(:,:,2) =

   39.5319    9.7468
   20.6565   20.9201
   28.9294   48.6970

>> 9 / rand(3,2,1)
Error using  / 
Matrix dimensions must agree.
 
>> 9 / rand(3,0,1)
Error using  / 
Matrix dimensions must agree.
 
>> 9 / rand(3,0,2)

ans =

  3×0×2 empty double array

>> 9 / rand(3,2,0)

ans =

  3×2×0 empty double array

>> 9 / rand(3,1,0)

ans =

  3×1×0 empty double array


current octave output:

octave:1> 9/rand(1,3)
error: operator /: nonconformant arguments (op1 is 1x1, op2 is 1x3)
octave:2> 9/rand(3,1)
ans =

   0.8999   3.8746   7.8228

octave:3> 9/rand(2,2)
error: operator /: nonconformant arguments (op1 is 1x1, op2 is 2x2)
octave:4> 9/rand(2,4)
error: operator /: nonconformant arguments (op1 is 1x1, op2 is 2x4)
octave:5> 9/rand(4,2)
error: operator /: nonconformant arguments (op1 is 1x1, op2 is 4x2)
octave:6> 9/rand(3)
error: operator /: nonconformant arguments (op1 is 1x1, op2 is 3x3)
octave:7> 9/rand(3,2,2)
error: operator /: nonconformant arguments (op1 is 1x1, op2 is 3x4)
octave:8> 9/rand(3,2,1)
error: operator /: nonconformant arguments (op1 is 1x1, op2 is 3x2)
octave:9> 9/rand(3,0,1)
error: operator /: nonconformant arguments (op1 is 1x1, op2 is 3x0)
octave:10> 9/rand(3,0,2)
error: operator /: nonconformant arguments (op1 is 1x1, op2 is 3x0)
octave:11> 9/rand(3,2,0)
error: operator /: nonconformant arguments (op1 is 1x1, op2 is 3x0)
octave:12> 9/rand(3,1,0)
error: operator /: nonconformant arguments (op1 is 1x1, op2 is 3x0)




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