README

datadac-1.3, June 2018

Datadec takes inductive (or recursive) data types modelled on those found in
functional languages (Hope, Miranda, Haskell etc) and generates ISO/ANSI C
code to implement them.

			Duncan C. White, d.white@imperial.ac.uk
			19th March 2002

New May 2014!  v1.2

- experimental free functions for every inductive data type
 (run datadec with new -f option)

New June 2018! v1.3
- converted to use stdbool.h at last, inside and out

- added new mode (-m) and new code to emit on stdout a list of all the
  metadata, i.e. for each shape of each type, typename, shapename, and
  the shape parameter types.  This will be useful for add-on tools such
  as the experimental "CPM.perl" script, which tackles client side use
  of datadec-generated types, translating C+Pattern Matches to C.

- added assert( p != NULL ) in every constructor after the NEW( T ) call.

- fixed longstanding bug whereby the top of the global section was
  copied AFTER the <<#include "thismodule.h">> whereas if it were copied
  above it could #include other stuff.  but of course now it can't use
  the defined types from "thismodule.h".

- changed the arg processing to use getopt.

- added a new "suppress function F" multi-flag, and stored the results in
  a "list (could even be a set) of strings of named functions to suppress,
  ie. perhaps because an alternative manually tweaked verson is included in
  the GLOBAL section."  Did this by importing strlist module from libADTs.

An Example of Datadec in Action
-------------------------------

To give you a feel for what datadec can do, you could write:

intlist = nil
        | cons( int first, intlist next )
        ;

illist  = nil
        | cons( intlist first, illist next )
        ;

idtree  = leaf( string id, illist l )
        | node( idtree left, idtree right )
        ;

What does this mean?  
The first rule declares that an intlist can take two basic "shapes" -
it is either empty, aka nil, or of the form cons(int,intlist).
nil() and cons() are called constructors, and define different
"shapes" that objects of the type can take.
However, because the second argument of a cons() constructor is itself
an intlist, this type is said to be recursively or inductively defined.

Functional programmers will recognise nil or cons() as the standard
way of defining a list, so more intuitively, intlist is simply
a list of integers!

Reading on, an illist is declared as a list of intlists,
and an idtree is declared as a binary tree where each leaf node
contains a (string, illist) pair.

Given this input, datadec can automatically construct an ISO C
module which implements all the data types, a constructor function for
each constructor, deconstructor functions to help you to take objects
apart again and printing functions to help you with debugging.

(Plus, new May 2014: a tree-walking free function for every type if you
invoke datadec with the new -f option).

Building and Packaging datadec
------------------------------

See the INSTALL file for building and packaging instructions.

Testing
-------

Having built datadec in the source directory, you can also compile and
run a test harness in the test directory.  test/cdata.in is the datadec
input file which declares some recursive data types (lists and trees),
and ctest.c is the test harness that uses them.  cd into test and run make
to turn cdata.in into cx.h and cx.c, and to compile cx.c and ctest.c and
link them..