I think strict adherence to such rules is silly. Some 20 lines functions are massively more complex than some 120 line functions. If the computation is simple

I think strict adherence to such rules is silly. Some 20 lines functions are massively more complex than some 120 line functions. If the computation is simple and linear, then long functions are fine. If there are nested loops and if statements and other forms of flow control and deep nesting, then long functions are painful.