Re: Wow, Lisp Reader !!

Wow, initially seems very nice! Thank you so much. I searched for alternate REPL’s the other day and did not find this. But I remember many years ago, maybe 10 years?, there was a project to make REPL’s into modular and pluggable designs. Maybe this is that project?

Thanks!


> On May 23, 2026, at 14:50, Kurt Geisel <[email protected]> wrote:
> 
> Saw this at ELSConf. Check out the protocols. But maybe you didn’t want to go this far 😉
>  
> s-expressionists/Eclector: A portable Common Lisp reader that is highly customizable, can recover from errors and can return concrete syntax trees <https://github.com/s-expressionists/Eclector>
>  
> - Kurt
>  
> From: [email protected] <[email protected]> On Behalf Of David McClain (as dbm at refined-audiometrics dot com)
> Sent: Saturday, May 23, 2026 2:40 PM
> To: Lisp HUG <[email protected]>
> Subject: Wow, Lisp Reader !!
>  
> Holy smokes… Common Lisp did such an amazing job with everything else, and especially CLOS. But now that I am old, I want to specialize the Lisp Reader for myself. I get really wearing not being able to enter DD:MM:SS for Right Ascensions and Declinations.
>  
> But gobsmack'ingly, the Common Lisp Reader is hugely resistant to customization. The HyperSpec hints that custom readers should be possible:
>  
> 2.1.4 Character Syntax Types
> 
> The Lisp reader <https://www.lispworks.com/documentation/HyperSpec/Body/26_glo_l.htm#lisp_reader> constructs an object <https://www.lispworks.com/documentation/HyperSpec/Body/26_glo_o.htm#object> from the input text by interpreting each character <https://www.lispworks.com/documentation/HyperSpec/Body/26_glo_c.htm#character> according to its syntax type <https://www.lispworks.com/documentation/HyperSpec/Body/26_glo_s.htm#syntax_type>. The Lisp reader <https://www.lispworks.com/documentation/HyperSpec/Body/26_glo_l.htm#lisp_reader> cannot accept as input everything that the Lisp printer <https://www.lispworks.com/documentation/HyperSpec/Body/26_glo_l.htm#lisp_printer> produces, and the Lisp reader <https://www.lispworks.com/documentation/HyperSpec/Body/26_glo_l.htm#lisp_reader> has features that are not used by the Lisp printer <https://www.lispworks.com/documentation/HyperSpec/Body/26_glo_l.htm#lisp_printer>. The Lisp reader <https://www.lispworks.com/documentation/HyperSpec/Body/26_glo_l.htm#lisp_reader> can be used as a lexical analyzer for a more general user-written parser.
> 
>  
> 
> And yet, there are no functions to allow interrogation of the Readtable for character syntax types corresponding to any particular character, except for those that are marked as macro characters.
> 
> Other, macro characters, like tic (apostrophe) #\’ should really only carry meaning at the leading edge of a symbol name. But it serves as a stopping delimiter in the Lisp Reader so that you cannot have symbol names like Thing and Thing’, without writing them as |Thing’|.
> 
> Interestingly, the colon character, #\:, which is used to separate package names from symbol names, is *NOT* shown as anything special in the HyperSpec. It is simply listed as a constituent character.
> 
> Maddeningly, LW chose to intercept this character with eager resolution, rather than allowing it to just become absorbed as a compound symbol token for later analysis. And there are no CL Hooks to be found that allows for alternate interpretations.
> 
> So I find it totally mystifying that this corner of Common Lisp should be so comparatively backwards.
> 
>  
> 
> [ I apologize if I come off too harsh. I cut my teeth on Forth, which has no restrictions, at the observatories many decades ago… ]
>