Pop3 connection with D

[Andrei Alexandrescu (See Website For Email)]

kris wrote:
> Andrei Alexandrescu (See Website For Email) wrote:
>> kris wrote:
>>
>>> Andrei Alexandrescu (See Website For Email) wrote:
>>>
>>>> Possibly implementing protocols could be an area in which DSLs might 
>>>> help, e.g. in the guise of automata and of course regex. I once 
>>>> designed a little DSL for implementing FTP and it was of great help.
>>>
>>>
>>>
>>> Compile-time DSLs?
>>
>>
>> Obviously.
> 
> That sounds reasonably sophisticated.
> 
> Just out of interest, how does one easily debug something like that?

Very easy. The FTP protocol is described as a collection of states with 
prescribed transitions in between them. A DFA (in C++) implemented them 
in a compact manner; whenever the DFA would bail out (by throwing), it 
would tell what state it was in, what was the expected input, and what 
the actual input was. I remember that library was a rewrite of a library 
written in a "old school" style from first principles (e.g. int and if 
and switch), meaning that following what the code does and where you are 
was horrendous. We were very pleased with the rewrite.


Andrei