I cannot read your blocks, but the error message is telling you that somewhere you are feeding the length of list block with a value and not a list.

Did you copy my code from the above link?

Did I miss a case?

Change the blocks language to English and post an aia export.

An image of a collapsed block is to a block as an egg shell fragment is to an egg

On further investigation, I found a spot in my matrix multiplication routine (calculation of limit_j) where I assumed a list of lists as one of the multiplicands, ignoring the possibility of a vertical column represented as a list instead of a list of single-item lists.

I need to review the rules of matrix multiplication before I can achieve correct response to such input.

If your intention was to multiply a column a1,a2,a3 by a matrix, you would need to represent the column as (decode it from JSON, for rigor)

column:[[a1],[a2],[a3]]

row: [a1,a2,a3]

P.S. Thank you for notifying me of the oversight.

Here is a revised version of your calls to the matrix multiplier routine, adding an extra layer to operand a.

(draggable)

This conforms with sample 2.1.6 of my source at

it is possible to multiply two matrices with different dimensions, if the number of entries in the rows of the first matrix is the same as the number of entries in the columns of the second matrix.