Some brief notes on developing with this code.

UUAGC is used in the type checking, there are some links at the top of
AstInternal.ag for more information.

The code uses a few GHC extensions, I don't know if they are
conservative extensions or not, see the cabal file and grep to find
out the current list.

Two of the files are generated:

DefaultTemplate1Environment.hs -> generated using
 ./HsSqlSystem.lhs readenv template1 > something && cp something ...
 You shouldn't need to regenerate this file unless you change the
 Environment data type.

AstInternal.hs -> this is generated from AstInternal.ag and
 Typechecking.ag using uuagc, see AstInternal.ag for the exact
 arguments to use.

If you are editing either of these generated files directly you're
probably doing something wrong.

See the file 'usage' which documents a bunch of utility functions you
can run from the command line, you can look and HsSqlSystem.lhs source
for some example usage.

There are rudimentary test for a lot of the functionality, see
ParserTests.lhs and AstCheckTests.lhs (for type checking). These
contain some small examples of how the code can be used. The
HsSqlSystem.lhs file contains a few more examples.

Source file overview:

HsSqlSystem.lhs

Main executable to provide command line access to library functions,
mainly utilities to help with developing the source. Run
'./HsSqlSystem.lhs help' to list the commands. You can run the
automated tests using './HsSqlSystem.lhs test'.

All the other source code is under Database/HsSqlSystem/

Database/HsSqlPpp/Utils.lhs contains some small utility functions.

The main folders under Database/HsSqlPpp are:

Ast: public modules which forward parts of the internal ast and
typechecking code

AstInternals: private modules for ast, annotations, typechecking, etc.
  also contains all the .ag files.

Commands: ErrorT wrappers for many library functions, used heavily in
HsSqlSystem.lhs

Dbms: Some rudimentary and half baked code to access databases.

Extensions: expermental code for a syntax extension system for plpgsql

HsText: code to help producing documentation: will process a text
file, extract commands, run them, and interpolate the output into the
text.

Parsing: the parsing code

PrettyPrinter: pretty printing code

Tests: hunit tests


Main code files:

The main parsing code is in Database/HsSqlPpp/Parsing/Lexer.lhs and
Database/HsSqlPpp/Parsing/Parser.lhs

The main pretty printing code is in
Database/HsSqlPpp/PrettyPrinter/PrettyPrinter.lhs and there is also
some code to insert types, etc. into the original source in
Database/HsSqlPpp/PrettyPrinter/AnnotateSource.lhs

The main ast and typechecking code is in the following files:

attribute grammar files:
Database/HsSqlPpp/AstInternals/AstInternal.ag contains the ast nodes
Database/HsSqlPpp/AstInternals/Typechecking/ contains the ATTR and SEM code
for type checking
These are supplemented by a bunch of helper modules:

Database/HsSqlPpp/AstInternals/TypeConversion.lhs - contains the code
which handles the implicit type cast resolution (these are postgresql
algorithms used to lookup function calls, work out the types of result
sets and check assignments).

Database/HsSqlPpp/AstInternals/TypeCheckingH.lhs - contains some code
which has been moved out of TypeChecking.ag for ease of development

Database/HsSqlPpp/AstInternals/AstAnnotation.lhs - contains the data
types and a few helper functions for the annotation data types.

Database/HsSqlPpp/AstInternals/TypeType.lhs - contains the data types
and a few helper functions for postgresql types, and also type errors.

Database/HsSqlPpp/AstInternals/AstUtils.lhs - contains some error handling utils

Database/HsSqlPpp/AstInternals/AnnotationUtils.lhs - contains some
additional annotation functions which depend on the ast nodes

the code to track environment changes during type checking
(e.g. catalog changes, variables/bindings) is in the following two files:
Database/HsSqlPpp/AstInternals/EnvironmentInternal.lhs - the main code
to create, update and use environments.
Database/HsSqlPpp/AstInternals/EnvironmentReader.lhs - code to read a
catalog from a database and produce an environment value.
Database/HsSqlPpp/AstInternals/DefaultTemplate1Environment.lhs - this
is a copy of the default template1 database environment

The code under Database/HsSqlPpp/AstInternals/ is hidden behind the
public modules in Database/HsSqlPpp/Ast/:
Database/HsSqlPpp/Ast/Annotator.lhs
Database/HsSqlPpp/Ast/Ast.lhs
Database/HsSqlPpp/Ast/Environment.lhs
Database/HsSqlPpp/Ast/Annotation.lhs
These pretty much just forward exports, and add a bit of haddock
organisation.

The hunit tests are in:
Database/HsSqlPpp/Tests/AstCheckTests.lhs
Database/HsSqlPpp/Tests/ParserTests.lhs
and also this file which isn't really used yet:
Database/HsSqlPpp/Tests/DatabaseLoaderTests.lhs

There are a few utilities to access databases in
Database/HsSqlPpp/Dbms/, this code is very sketchy.

These files all have (hopefully) useful comments, although many of
these haven't been kept up to date.

The error handling in the type checking code is in flux so quite a lot
of the code there is a bit of a mess unfortunately (I'm still not sure
what the best way to do this is.).

Also, some of the annotation functions use SYB which I'm a bit crap
with so that code is also a bit of a mess.

The test coverage isn't really great, but it's not bad (this will be
fixed at some point).

The bits which I hope aren't too bad are the ast node data types, the
parser code, and the catalog code.