Iterator refactor [3/N]

[willGraham01]

Attempting to do some small refactors to iterator.cpp that don't touch anything that will need to be touched by #70. Docstrings are added to all refactored functions, classes, etc.

List of replacements:

checkPhasorConvergence

Replaced with the Field class method max_pointwise_difference_over_max_element. The name of the old function is misleading, it is only computing an error metric and NOT checking convergence - this happens later in the iterator.cpp main loop.

Pulling this out into a class method to make things a bit cleaner. Also, both the inputs are Fields, and the function is asymmetric, so it makes sense to have this as a class method.

setGridLabels

Changed to the initialise_from method of the GridLabels class.

is_dispersive_ml

Changed to is_dispersive method of DispersiveMultilayer class.

is_conductive

Superceeded by the all_elements_less_than method of the XYZVector class. The check for whether a material is conductive is just whether at least one entry of an XYZVector exceeds a particular threshold.

[samcunliffe]

👍

[samcunliffe]

So we can have a non-dispersive dispersive multilayer? (DispersiveMultiLayer::is_dispersive == false)

[willGraham01]

Apparently so - there's a corresponding call in iterator.cpp. I don't have the same feel for everything in iterator.cpp yet like Tom did, so I'm guessing its an oddity for us to be in this case rather than common.

There's also another is_dispersive function for the background material (which doesn't have its own class) too.