Flexible Default Function Parameters via structs with Nullable Fields

[Mike Parker]

Victor Porton shows how he uses string mixins to generate structs 
with Nullable fields at compile time to help him pass arbitrary 
subsets of explicit and default arguments to functions in D.

The blog:
https://dlang.org/blog/2019/04/29/flexible-default-function-parameters/

Reddit:
https://www.reddit.com/r/programming/comments/bip83x/flexible_default_function_parameters_in_d/