Recently I shared a Matrix Multiplication Power Query technique here, and explained how to use List.Generate as the core step of the multiplication.
It was fun to experiment with List.Generate and use it to implement a kind of a For-Loop. So I thought it would be cool to use List.Generate to iterate over a nested loop.
Below you can find the function that I created. You can use it to implement a kind-of-a-nested-loop in Power Query.
The arguments RowCount and ColumnCount represent the number of iterations for the outer and inner loops, respectively. To better explain my code, you can think of it as a function that performs operations on all the cells in a table, starting with the first row, iterating over the cells of each column in the specific row, then jumping to the next row, and so forth.
fnIterateNestedLoop = (RowCount, ColumnCount, fnTransformByIndices) => List.Generate( ()=>[i=0, j=0], each [i] < RowCount, each if [j] < ColumnCount - 1 then [i=[i], j=[j]+1] else [i=[i]+1, j=0], each fnTransformByIndices([i], [j]) ),