Re: s48_extract_string?

On Tue, Mar 3, 2009 at 5:12 PM, Richard Kelsey <[email protected]> wrote:

>   Date: Tue, 3 Mar 2009 16:08:37 -0500
>    From: Donald Allen <[email protected]>
>
>    A few comments:
>
>   1. I'm failing to understand why what works in the REPL doesn't work when
>   loading from a file.  In other words, why is
>
>   ,open external-calls
>   ,open load-dynamic-externals
>
>   acceptable when typing to the REPL and not acceptable when loading a
> file?
>
> It is acceptable when typing to the command interpreter and
> not when loading a file.  Scheme48 provides no way to read
> commands from a file using the , syntax of the command
> interpreter.
>
>   2. As for whether it's a new language, that depends on how you define
>   "language" (sounds Clintonesque :-). Sure, it's Scheme syntax, but in
> order
>   to say what I want to say in normal Scheme acceptable at the REPL, e.g.,
>
>   (load-dynamic-externals "/home/dca/Scheme48/postgresql.so" #f #f #f)
>   (import-lambda-definition pg_open_connection (dbname))
>
>   I now need to wrap in a call to 'run' when loading a file. To me that's
> new
>   language -- things need to be said differently.
>
> No, you need to wrap them in a call to 'run' when loading
> them into the exec package.  Why would you expect to get the
> same behavior if you type
>
>  (load-dynamic-externals "/home/dca/Scheme48/postgresql.so" #f #f #f)
>
> into the REPL, which evaluates it in the user environment,
> and if you put it in a file and load it into the exec
> environment?


I wouldn't expect to get exactly the same behavior. In the first case, I'd
expect the dynamic-externals to be loaded into the user environment; in the
latter case, I'd expect them to be loaded into the exec environment. But why
would I expect to have to use different syntax in the two cases?

Also, I quote from the very example cited in the documentation, namely
scheme/vm/load-vm.scm:

(user)
(open 'ps-memory)
(open 'vm)
(open 'heap-init)
(open 'read-image)
(open 'memory-debug)

(run '
(define (start-vm image-file heap-size stack-size start-args)
  (reinitialize-memory)
  (s48-read-image image-file heap-size)
  (s48-initialize-vm (allocate-memory stack-size)
             (quotient stack-size 4))
  (s48-call-startup-procedure start-args
                  (vector-length start-args)))
)

(user) means we are now loading into the user environment, yes?  So the
function start-vm is going to end up in the user environment. Correct? So
again, my bottom-line question -- why does the define have to be wrapped in
a run (especially when the documentation of run tells you absolutely
nothing: "evaluates the expression, prints the result, and makes it the new
focus object"; well, typing an expression at the REPL does the same thing,
so what value is run adding? Can't tell from the manual.) when it lives in a
"command file" when that is unnecessary when typing at the REPL.



>  If you want the same behavior you need to load
> it into the same environment that the REPL uses.  Your command
> file has code that needs to be run in two different packages,
> the exec package and the user package.  There has to be some
> way to distinguish them.  The command interpreter does this
> by seeing the initial comma.


Exactly. And my contention is that the distinction ought to be made the same
way when loading from a file. They're bytes; they're just coming from a
different place.

>
>
> It would probably be clearer if the command interpreter didn't
> treat forms without initial commas as having a ,run in front
> of them.  If you had been required to put in all of the ,runs,
> the correspondence between the command interpreter and the
> exec package would have been clearer:
>  ,open external-calls
>  ,open load-dynamic-externals
>  ,run (load-dynamic-externals
>       "/home/dca/Finances/Invest/Options/Scheme48/postgresql.so" #f #f #f)
>  ,run (import-lambda-definition pg_open_connection (dbname))


Exactly the opposite. Leave the command interpreter as it is and use it to
read from files.

/Don

>
>
>
>                                            -Richard Kelsey
>