Replacing compiler implementation, D
=====================================

Your project is to replace the entire Pleasant compiler with a version in D.

All of the compilation will need to be changed from calling a C compiler to
invoking the dmd compiler.

You should not need to keep most of the "necessary.c" and
"necessary.h" files since the code is, well, unnecessary in D since D
has native support for lists and associative arrays, and almost all of
the code currently in necessary.c is just boilerplate to implement
those.

Even better, all of the D native versions of lists and associative
arrays can use (and, by default, will) automated garbage collection,
so you don't have to worry about deallocation issues.

However, there is a little bit of code in necessary.c that implements
some semantic functionality, (mostly relating to scopes) that you will
need to incorporate somewhere. (I would suggest adding to the
beginning or end of your parser.dmd file)

Like the Python and Perl versions, you will have to deal with Unicode
issues, but you can largely keep the current the same lexing strategy
as the C version.