[slime-devel] buffer readtables

Helmut Eller heller at common-lisp.net
Mon Sep 28 06:23:41 UTC 2009

* Sidney Markowitz [2009-09-27 22:13+0200] writes:

> Helmut Eller wrote, On 28/9/09 7:21 AM:
>> First let me say that I have little sympathy for custom readtables.
>> People who use custom syntax are fighting their tools.
> Can you say a little more about this? The only time I've used a custom 
> readtable was when I was implementing a custom non-Lisp language for the 
> application that was purpose-designed for the applications and its 
> users, using a custom readtable and macros to translate the application 
> language into s-expressions and then taking it from there in Lisp. One 
> advantage was that user scripts could be compiled into fasls.
> I didn't have a problem with the result, but I would like to hear the 
> arguments for doing it a better way if I ever do something similar in 
> the future.

Typical problems with custom syntax:

- it's harder for the compiler to track source locations.  Some
  compilers, e.g CCL, use the reader to mark source expressions with
  file positions.  With custom readtables that's not done.

- many people forget about *read-suppress* 

- the editor can't indent the code or it must be told how to do so

- the readtable is part of the compile-time environment and tools like
  ASDF must be told how to deal with it

- after a month of absence even the author has forgotten how the reader
  marco was supposed to work


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