[cdr-discuss] Re: [RfC] WITH-READTABLE-ITERATOR

[Ariel Badichi]

"Tobias C. Rittweiler" <tcr at freebits.de>
writes:

>   Ariel Badichi proposed coalescing a generator's fourth return value
> (indicating if the returned character is a dispatch macro character)
> with its first return value (indicating if the generator is
> exhausted.)
>

An example of the results returned by the generator, according to my
proposal, would be:

  :MACRO-DISPATCH-CHAR, #\#, #<FN>, (...)

Rather than:

  T, #\#, #<FN>, T, (...)

I find the former more intelligible.  I also find, however, that Stephen
Compall has made a strong argument in support of the interface proposed
in the draft.  If I understand him correctly, it is that there are (and
always will be) just two kinds of macro characters, dispatching and
non-dispatching, and that by using a boolean to discriminate between
them, we save the user the work of mapping them herself in many cases.
In light of this argument, I am ready to cope with the unpleasant
consequences of the draft's proposal.

>   Exceptional Situations ......................
>
>   Signals an error of type `program-error' if a MACRO-CHAR-TYPE is
> supplied that is not recognized by the implementation.
>

The outcome of having a non-symbol given as a generator name is not
specified.  Might it also be the signaling of a `program-error'
condition, or should it remain unspecified?

The outcome of having a non-readtable given for iteration is not
specified.  Should it be the signaling of an error, or should it remain
unspecified?

Ariel