Re: procedure-source availability

[Mark H Weaver <mhw@netris.org>]

On 09/30/2012 04:11 PM, Panicz Maciej Godek wrote:
> I've found a bug report on savannah, which noted the lack of
> ``procedure-source'' for guile 1.9.11
> http://savannah.gnu.org/bugs/?30469
> I wonder if any further decisions were made regarding the maintenance
> of ``procedure-source''. I would find it really useful for my
> application if the sexp containing the lambda expression that was used
> to generate the procedure was stored in it's property list, and I
> don't understand why this isn't currently done.

Out of curiosity, why do you need this?

The reason I ask is that, in the presence of macros, it is not clear 
what you mean by the "procedure-source".

Do you mean before macro expansion?  If so, what use it is to you, since 
it may contain user macros that your code cannot understand? 
Furthermore, many procedures simply don't exist before macro expansion. 
  For example, a record type definition expands to several procedure 
definitions that do not exist in the original source.

If you mean after macro expansion (or perhaps in some intermediate state 
of macro expansion, e.g. at the point where the macro expander first 
encounters the lambda expression), then a normal sexp with the original 
identifier names is no longer sufficient.  In psyntax, these 
intermediate forms are represented as syntax objects, but at the very 
least you'd need to rename the identifiers to prevent unintended 
variable capture.

It's a very thorny issue, and I suspect that's the reason that 
'procedure-source' no longer works.  If we are going to reimplement that 
functionality, then we first need to figure out precisely what it 
_should_ do in the general case.  Which brings me back to the question: 
"Why do you need this?"

     Regards,
       Mark