On Nov 11, 2012, at 8:38 PM, Walter Bright <walter@digitalmars.com> wrote:
>
> Yes, adding const in would probably be an easy and effective change. Too bad C++ has no purity :-(

I've always thought an up and coming language should have a tool to automatically convert to C or C++ code. That allows support for all platforms supported by C/C++ and making a self-hosted compiler.

How hard would a D to C++ converter be? I think ABI compatibility would be impossible, but might not be too big of a limitation. If such a thing existed, is it possible to incrementally convert pieces of the compiler to D?

I have in the past explored two other options:

1 - Automatically convert the compiler to D. I had a go at this a while back with quite impressive results. dmd only uses a small, D-like subset of C++ which makes it possible. I managed to generate d code for the frontend with some minor tweaks, then got stuck on the backend's prolific use of #ifdefs halfway through expressions. This is not insurmountable, you just need to process the #ifdefs before trying to parse the code instead of trying to convert them to static if/version. At that point, I took a break to explore:

2 - Enhance D's ability to link with a subset of C++, then refactor the compiler until parts can be pulled out and ported to D. The ultimate goal would be to have the backend as a C++ static lib that is linked against a frontend written in D. I did a little bit of work on this at the beginning of the year but reached the limit of my backend knowledge, this needs debug info/mangling/codegen support.

On 11/11/2012 6:51 PM, Jason House wrote:

How hard would a D to C++ converter be? I think ABI compatibility would be impossible, but might not be too big of a limitation.

My experience with the microd experiment shows that creating a D to C++ converter is not actually that difficult, so long as you're not trying to produce idiomatic (or even readable) C++. Most of D's features can be lowered to C++ features (because they are C++ features).

On Sunday, November 11, 2012 19:54:30 Walter Bright wrote:
> On 11/11/2012 6:51 PM, Jason House wrote:
> > If such a thing existed, is it possible to incrementally convert pieces of
> > the compiler to D?
>
> That would leave the specter of having two headers for the data types, one
> in D and one in C++.

Header generation can be automated.