guile unify further improvements.

[Stefan Israelsson Tampe]

Coding has been gong on many levels.

1.  A macro validator and error reporting mechanism similar but simpler then syntax-parse has been tested
2.  A macro framework to generate c-code form scheme forms using fmt and scheme macros has been developed
this macro system has good error reporting and uses 1 to output errors in macro formations (check out language/clambda
in the guile unify repo if you want to see examples of how it is used. Also line numbers is emmited to the output c-code
so that the errors reported by the c compiler can be traced.
3. type checker developments.
4. investigation of adding type information to tree-il
5. The guile unify system uses stacks in various ways and a development to make a c library to handle stacks in various ways.

To test out using the scheme forms to c code generation framework a system to easy usage of the SCM environment under C
is tried. Here we try to make simple match macros and macros to create lists almost like creating lists in scheme together with
constant collection in order to collect say floating point constants symbols strings etc. then declare those constants associated
with a SCM variable and init those in a init function. That way we can use the SCM variables (constants) inside the c-code. I don't know if such a system is in place already but it's kind of cool to try it out. This way there is some tools that eases c-code generation. Not to replace the longtime goal of a scheme only solution. It's all a play with the tools at hand and have fun at the same time.

The syntax parse like code is really really small if one uses a nice match tool. It's located under parse/. directory in the guile unify repo. It's all about introducing checks in a schematic that makes it obvious what is checked and what is not checked in a macro form.

I've been playing with typechecking recursive types and have an algorithm that I think avoids infinite recursions for non recursive
fuctions. To be done is to make it possible to typecheck the map function. The main difficulty with that is that it has a type
signature that depends on the number of arguments in a non trivial way. and to solve this one need to handle a type parameter
of the form B ... , e.g.

map:
(lambda ((lambda (B ...) -> A) (list B) ...)) -> (list A))

which is cool form of recursion.

/Stefan