Why is D unpopular?

[Walter Bright]

On 5/15/2022 4:55 AM, H. S. Teoh wrote:
> There is, of course, the option of rewriting said C library in D.
In my experience, it is not an option to rewrite working C code into D.

Note that I have successfully converted small and medium C code projects to D. 
I've done other translations of programs from one language to another.

1. if you don't have a test suite for the program, a successful conversion 
becomes an order of magnitude harder

2. converting a program all at once does not work. It must be done 
incrementally, one function at a time

3. even so, when faced with a large, complex project, there's just no business 
case for doing a conversion

Even just converting the .h files to D can be a major, rather unpleasant 
undertaking. We've put a lot of time into converting the various system .h files 
into D for druntime. There's always a risk of a mistake, and we've made them and 
the result is bizarre crashes because of ABI mismatches. Hand-checking them is 
error-prone, tedious and very boring work.

ImportC makes things so much easier. You can write new D code and hook it up 
with your existing C code base. You can get reliable, easy, and accurate access 
to .h files. D will happily work with a project that's a patchwork of C and D code.

I.e. it dramatically lowers the barrier to adopting D.

As for languages other than C, they routinely have a C interface. ImportC makes 
it easy to hook up with them via the C interface they provide.