Re: SXML-to-HTML-ext.scm issues

Hello!

> 1/ this file has 2 functions of general utility: lookup-def and 
> signif-tail. I think these belong in util.scm not here because they have 
> general usefulness

I'm afraid I'm not sure that signif-tail is so general. It seems
quite ad hoc. If I thought harder I might have gotten by without
it. As to lookup-def, I agree about its utility. I seem to be writing
something like that in almost every other file of my code. Alas, all
those lookup-def are slightly different. For example, the associative
list to look up in can be specified either as 
	((key . value) ...)
or as
	((key value) ...)
the former is more common, in my experience. Yet the lookup-def in
SXML-to-HTML-ext.scm uses the latter for obvious reasons. Also, what
to do when the key is not found and there is no default? Sometimes I
want to abort the execution because it just can't continue. Sometimes
I wish to print a warning message and return #f. Sometimes I just wish
to return #f. How to specify the default value or the lack of it is
also not clear. Sometimes #f as 'no default' is OK. Sometimes I make
the default argument optional. Sometimes specifying the default as a
thunk is beneficial (cf. SRFI-44). 

So, while lookup-def is certainly a useful function, what is the best
interface for it remains totally unclear to me....

> (define (lookup-def key alist default-value . warn?)
Incidentally, you might find (define-opt ...) useful in this
case. Please see myenv-chez.scm or myenv-bigloo.scm.

> 3/ Is is possible to checkin util.scm and SXML-to-HTML-ext.scm with my 
> suggested mods? I would like to stay synchronized with the standard 
> repository for these functions.
> 4/ Will Kiril's PLT version also have my updates if they get checked in?

Michael Sperber is currently doing adjustments to the code to make
sure everything is R5RS, and works in Scheme48 and PLT Scheme. He is also
writing module declaration and interfaces, for Scheme48/PLT module
system. That is a lot of work. The module system of Scheme48/PLT is
very expressive, and so it makes the structure of the SSAX-SXML code
far clearer. Perhaps we should wait making other changes until that
job is finished. A more detailed message about the adjustments and
modularization is forthcoming. 


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