More complexity creep in Phobos

[Andrei Alexandrescu]

On 3/27/19 11:22 PM, Meta wrote:
> It seems like if you see some weird code in Phobos but you don't 
> understand why it was written that way, there are 3 main reasons that 
> account for 99% of these cases:
> 
> - string (autodecoding)
> - alias this
> - enums

"Mistakes made by people" is missing from that list. Which include mine 
of course.

There's this nice notion of reasoning by first principles vs. reasoning 
by analogy:

https://fs.blog/2018/04/first-principles/

A very nice essay - recommended outside this discussion's context, too. 
The levenshteinDistance issue is a direct application of the two kinds 
of reasoning. This is reasoning by analogy:

"DirEntry converts to string and is used by some people as such. They 
pass it to functions, and some accept it but some don't. It follows by 
analogy that the Levenshtein distance algorithm should be worked out to 
accept it, too."

In contrast, the reasoning from first principles should powerfully 
override that:

"Levenshtein distance operates on forward ranges. All that stuff that 
changes the signature of levenshteinDistance to accept other artifacts 
is nonsense. Whoever wants to use it should carry the conversion to 
forward range themselves."

It follows that the correct answer to this generalization frenzy should 
be: "We work with ranges and character types. If you've got enums and 
alias this and whatnot, more power to you but to use the standard 
library you must convert those to the stuff we support."