WIP: 30 arithmetic assignment operators for fields

[bevanwsjones]

PLEASE MERGE #33 first

Field:

• adds arithmetic assignment operators to Field.
• moves arithmetic operator out of Field as standalone operators, defined in terms of the above operators.
• added copy constructor and empty function.
• fixed by with setSize function.
• Testing made more granular.

[greole]

What is the state of this PR, should we pick it up again?

[bevanwsjones]

What is the state of this PR, should we pick it up again?

Want to get #45 in first so we can do some assert checking on the executors.

[bevanwsjones]

@greole to complete this merge I think there are two ways to go:

1. Develop an 'error' handling strategy and add it in through a separate merge request. We can go simple for now, but at least give it some 'formality'.
2. I just put some 'if statements' in to check executor equality and exit if they are not the same.

I think we should do a quick rough implementation now because the later we leave it, the more it will be that 'custom' approaches will crop up all over the code base. I also don't think we need to be too fine-grained about it. In my experience the message, line number, and file are good - a stack trace would be great but probably too much for now. A switch for certain checks to be done in 'debug' and 'release' mode. Thoughts?

[greole]

Develop an 'error' handling strategy and add it in through a separate merge request. We can go simple for now, but at least give it some 'formality'.

If possible I really would like to have some stack trace feature. Unfortunately std::basic_stacktrace is a c++ 23 feature https://en.cppreference.com/w/cpp/utility/basic_stacktrace.

Maybe we can take a look at https://github.com/bombela/backward-cpp or https://github.com/jeremy-rifkin/cpptrace. I guess that should be a different PR though.

[greole]

@bevanwsjones since you're working on this. field could use a std::pair<size_t,size_t> field::range() {return {0, size()};} function.

[bevanwsjones]

@bevanwsjones since you're working on this. field could use a std::pair<size_t,size_t> field::range() {return {0, size()};} function.

done