TCL->Scheme

[Ian Bicking <ian@bickiia.earlhall.earlham.edu>]

I've been working on a TCL to Scheme translator, and I have a few
questions to throw out there.

Is there anyone else actively working on translating languages to
Scheme?

I've heard references to being able to use gdb to debug Scheme/Guile
source.  Is this true?  Can someone point me to how I can do this?

I'm trying to figure out how to integrate TCL and Scheme code -- in
some ways it seems hopeless.  However, that aside, maybe there's some
ways to do some of these things:

How can I convert a string to a variable.  E.g., if the TCL tries to
call a variable "*some-variable*" how can I use that string to get the 
value of *some-variable?

How can I define a variable based on a string?  E.g., if the TCL
wishes to export some procedure, how can I put that procedure's name
in the global namespace?

Can anyone see possible solutions to the type problem -- i.e., that
TCL has only one type (strings)?  I think this will be a general
problem for translated languages, because the type system of one
language won't translate one-to-one to the type system of Scheme.  If
it is staticly typed you can munge your way around this, but most
scripting languages aren't statically typed.

The specific problem is that if a TCL program tries to call a Scheme
program, how will it pass its arguments?  

A TCL string can be a list:
"1 2 {3 4}" -> '(1 2 "3 4"), or maybe '(1 2 (3 4))

A number:
"432.4e4"

A channelId (a port):
"file3"

A block:
"{puts hello ; puts world}"

A variable reference:
"x" as in "set x YYY"

And, of course, a string.  There's probably a number of other things
it can be as well, all depending on the context.  Even if some of
these data types are not stored internally as strings, they are still
essentially strings.  For instance this:

string compare [list member1 member2] "member1 member2"

Must be true (and all the more subtle ways of expressing the same
thing).

One possiblity, of course, is to make any callouts by the TCL program
use special type-identifiers.  For instance:

scheme:append [scheme:list "member1" "member2"] [scheme:list "member3"]

It would be nice is there was something cleaner, though.  Maybe there
isn't.


So, those are my questions.  Hopefully you all can help me out.  

So far the translation seems like it's going fairly well -- I'm using
a TCL interpreter written in Scheme, then applying a partial evaluator
(Similix
http://www.diku.dk/research-groups/topps/activities/similix.html).  I
don't think there's really any other reasonable way to translate TCL,
it being so context sensitive.  (I don't know how they byte-compile
TCL -- the language seems practically designed to make it hard to
compile by convential means).

<------------------------------------------------------------------->
< Ian Bicking                 |  bickiia@earlham.edu                >
< drawer #419 Earlham College |  http://www.cs.earlham.edu/~bickiia >
< Richmond, IN 47374          |  (765) 973-2824                     >
<------------------------------------------------------------------->