[plt-scheme] Can a module tell if it's being run interactively?

From: Matthias Felleisen (matthias at ccs.neu.edu)
Date: Tue Apr 15 19:42:16 EDT 2008

At some point Robby will turn into a systems guy and produce a full- 
fledged virtual script IDE. In the meantime, you may wish to consider  
turning your input for debug mode into a command-line argument and  
supplying them via the language menu (details) so you don't have to  
re-type them and so you don't have to remember to comment out  
anything when done debugging.

(Unless your input is truly large.) -- Matthias

On Apr 15, 2008, at 7:12 PM, Richard Cobbe wrote:
> Is there a way for code in a module to tell if it's being run in the
> DrScheme REPL or as part of a script?
> Right now, I'm trying to debug a script that reads input from stdin  
> and
> writes output to stdout.  I've got the file structured as follows:
>     #!/path/to/mzscheme
>     #lang mzscheme
>     (define (run)
>        (pretty-print (munge-input (read))))
>     (define munge-input ...)
>     (run)
> Now, If my script hits a bug, my first idea is to load the module into
> DrScheme -- which immediately stops, waiting for input.  The input  
> to the
> script is larger than I want to type at the REPL, so I comment out  
> the call
> to `run', reload the module, then do (with-input-from-file ...  
> run).  After
> I get the bug fixed, I inevitably forget to uncomment the call to  
> run, so
> the script is a NOP the first time I run it.
> It'd be really handy to say something like
>     #!/path/to/mzscheme
>     #lang scheme
>     (define (run)
>       (pretty-print (munge-input (read))))
>     (define munge-input ...)
>     (unless (running-at-repl?) (run))
> where `running-at-repl?' is provided by the "scheme" language.   
> That way,
> `run' gets called when I run the script from the Unix shell but not  
> when I
> load it into DrScheme and hit the "Run" button.
> OCaml's Sys.interactive
> (http://caml.inria.fr/pub/docs/manual-ocaml/libref/ 
> Sys.html#VALinteractive)
> is basically what I'm looking for here.  In OCaml, one can write  
> something
> like
>     let _ =
>       if not !Sys.interactive
>       then run ()
>       else ()
> at module top-level to get the behavior I described above.
> Is this possible?  If not, would it be possible to add this feature?
> Thanks,
> Richard
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