Common format for all derived types

[njansson]

(Based on the discussion in PR #720 )

Neko uses various ways of initialising objects, as shown below. Before the code grows too big, it would probably be a good idea to agree on a common format and make changes throughout fo
r the next-next release (v0.6)

The various formats are shown below

type(apa_t) :: blargh

! F90 style
call apa_init(blargh, args)

! type bound procedures  
call blargh%init(args)

! type interface 
blargh = apa_t(args)

Overhead costs of type bound procedures aside, my biggest issue with enforcing all derived types to have init() methods is the somewhat reduced readability of the code's intent. Both the f90 and interface indicate what kind of type myapa is when calling the initialisation method. Any other thoughts?

[timofeymukha]

I would strike out the F90 option. Both init and the interface look fine, I think. Not sure I agree about the intent though, because to me the type interface is slightly more confusing, since it is an assignment. But since all type names have a _t in the end, I think confusion with a regular function call is more or less impossible anyway. So I would just pick other init or interface and go for it!

[njansson]

The ide with the interface was to kind of mimic C++, myapa = new Apa(args) to at least see what the type is about. I did a test with only using init() and it quickly became rather unreadable.

[timofeymukha]

Let's go for the type interface, then unless others disagree strongly :-).

[timofeymukha]

@njansson
https://github.com/fortrancon/workshop2020/blob/master/doc/tmu_constructors-and-patterns.pdf
Slide 5