Alternatives to OOP in D

[monkyyy]

On Monday, 1 September 2025 at 13:58:23 UTC, Brother Bill wrote:
> I have heard that there are better or at least alternative ways 
> to have encapsulation, polymorphism and inheritance outside of 
> OOP.
>
> With OOP in D, we have full support for Single Inheritance, 
> including for Design by Contract (excluding 'old').  D also 
> supports multiple Interfaces.
>
> What would be the alternatives and why would they be better?
> I assume the alternatives would have
> 1. Better performance
> 2. Simpler syntax
> 3. Easier to read, write and maintain
>
> If possible, please provide links to documentation or examples.


> claims to not start flame wars

Its the wrong question you should answer 3 questions:

1. where is the data
2. how does data mutate
3. how do I control flow

oo is bad because its answers all three questions as **a noun**; 
"Im just going to vistor pattern my gamestate manager with my 
mailboxes"

to *start with* Id suggest 2 different styles:

1. going full ranges(standard)

This is a mostly functional style, theres nothing enforcing you 
to be pure, but first class functions is just how `.map` works. 
"Ranges are views of data", so the data stays where it started, 
if you start with a File(...).byLineCopy, the data is in the 
file, same with a json parser that provides a range interface. 
You mutate data with maps and reduces, and you manage control 
flow with take, drop and sort

2. plain old c

You have global scope, malloc and goto. You can at any time make 
all your data in global scope write a giant function; if you must 
allocate, call malloc, you just go edit data directly and you can 
do any control flow with goto as its the only thing hardward can 
do.

The answers the the 3 questions are mix and matchable.

---

Polymorphoism isn't remotely owned by oo, templates are more 
polymorphic, usually "upgrades" to templates like "generics" are 
about **preventing** their full polymorphic; contracts, generics, 
all this talk about function attributes, all of it is trading off 
the flexibility of templates to chase some safety.