Pascal2D

Pascal2D is a transcompiler that translates ISO 10206 Extended Pascal (EP) to D, with support for some non-standard Prospero extensions.

The goal is to translate around 500 kloc of proprietary source code, see the DConf 2017 talk (with continuation) for some background information. You can also read how an engineering company chose tomigrate to D.

Current status

What you see here is the initial development of Pascal2D, developed in open source prior to the decision of SARC to go ahead with translation of all its EP code. For the time being, SARC management has decided to fund further development off-line. If you have any interest in this project, for any reason, please do get in contact, we'd love to hear from you. We are very reasonable people and I'm sure we can work something out.

Getting started

Given you have installed a D compiler and a git client, clone the Pascal2D repository and do

cd Pascal2D
dub build

This will produce the pascal2d executable that can then be used to translate a Pascal source file, say example.pas, like so:

pascal2d example.pas > example.d

Optionally, the syntax tree of the Pascal file can be produced in HTML format by passing the --syntax_tree or -s argument.

Minimal example

In examples/hello/source/hello.pas you will find this Pascal source:

program hello(output);

begin
    writeln('Hello D''s "World"!');
end.

Calling dub in that directory

cd examples\hello
dub

will translate, compile and run that file. The translated file ends up in examples\hello\source\hello.d and looks like this:

import std.stdio;

// Program name: hello
void main(string[] args)
{
    writeln("Hello D's \"World\"!");
}

Compatibility library epcompat

Translated sources depend on the epcompat sub package, which is a library that provides type compatibility with and implements features of Extended Pascal. Some of its modules can be of value in hand written D code as wel, the epcompat API is available online.

Array example

In Extended Pascal, arrays can start at any index value. The example examples/arraybase shows how this is translated, including writing such array's to binary file. This is the Extended Pascal source:

program arraybase(input,output);

type t = array[2..20] of integer;
var a : t;
    n : integer;
    f : bindable file of t;

begin
  for n := 2 to 20 do
    a[n] := n;
  writeln('Size of t in bytes is ',sizeof(a):1);
  if openwrite(f,'array.dat') then
    begin
      write(f,a);
      close(f);
    end;
end.

Calling dub in that directory translates this into the following working D code, using dfmt to fixup formatting:

import epcompat;
import std.stdio;

// Program name: arraybase
alias t = StaticArray!(int, 2, 20);

t a;
int n;
Bindable!t f;

void main(string[] args)
{
    for (n = 2; n <= 20; n++)
        a[n] = n;
    writeln("Size of t in bytes is ", a.sizeof);
    if (openwrite(f, "array.dat"))
    {
        epcompat.write(f, a);
        close(f);
    }
}

Running tests

The following script will run unit tests, transcompile examples, run them and check their output to make sure they work as expected:

rdmd runtests.d