Temporarily disable all purity for debug prints

[Nick Sabalausky]

"bearophile" <bearophileHUGS at lycos.com> wrote in message 
news:invrod$3182$1 at digitalmars.com...
> From what I am seeing, in a D2 program if I have many (tens or more) pure 
> functions that call to each other, and I want to add (or activate) a 
> printf/writeln inside one (or few) of those functions to debug it, I may 
> need to temporarily comment out the "pure" attribute of many functions 
> (because printing can't be allowed in pure functions).
>
> As more and more D2 functions become pure in my code and in Phobos, 
> something like a -disablepure compiler switch (and printf/writeln inside 
> debug{}) may allow more handy debugging with prints (if the purity is well 
> managed by the compiler then I think disabling the pure attributes doesn't 
> change the program output).
>

That's a very good idea. I'm a huge fan of printf-debugging (comes from 
years of developing on platforms that didn't have a good readily-available 
debugger), so not being able to do that in pure functions would be a very 
critical roadblock for me for using purity. In fact, it's already been a 
royal PITA for CTFE.