[Larceny-users] Is this a fixed bug in larceny > 0.96?

[Felix Klock]

David-

On Jul 17, 2009, at 5:34 AM, David Rush wrote:

> It seems that if I examine a cyclically linked data structure in
> Larceny's debugger, I will never see another command prompt. This
> turns out to be mind-bogglingly annoying, and I was wondering if it
> was a known bug, or if there was some setting which might ameliorate
> it?



I recently had to wrestle with this behavior when interacting at the  
REPL.

I suspect it qualifies as a known missing-feature, rather than an  
outright bug [1]

----

There is a print-circular library in lib/Experimental.  In my case, I  
was able to load that up and then hook it into the repl-printer  
parameter, but that does not solve your problem, because the  
debugger's printer (which is distinct from the REPL's printer) cannot  
currently be overridden by the user.

Perhaps we should make the debugger's printer a user-settable  
parameter.  Do you think that would suffice for your needs?

(The debugger infrastructure really is pretty minimal, for better or  
for worse; you might be just as well off in the short term making your  
own copy of the source code in lib/Debugger/ that uses print-circular.)

-Felix

[1] In my ideal hypothetical world, cyclic structure would be  
transparently handled by the write procedure that the debugger is  
already invoking.  My impression is that the current (but undesirable)  
behavior (of Larceny's write procedure) is allowed by the R6RS, but am  
not sure (questions arise about whether a cyclic structure is a datum  
value as described in section 1.10; assuming a cyclic structure is not  
a datum value, then the next question is how to interpret the word  
"should" in the first sentence "Datum should be a datum value" in the  
description of the put-datum procedure, which serves as the  
specification of the write procedure in the R6RS.)