Re: Issue PATHNAME-PRINT-READ, v1, and then some

[Dan L. Pierson <pierson@mist.encore.com>]

    I would strongly prefer that a more generic approach be taken to
    allocating reader syntax.
    
I agree.  We really need to split the possible read macro characters
not given a meaning in CLtL into three groups:

    1. Potential Common Lisp extensions.  Your idea of #T as the only
       hook here makes some sense.

    2. Potential implementation extensions.  I favor a small set of
       of characters here as well.

    3. Reserved for user extensions. 

This isn't as easy as it may seem.  One problem is what happens when a
popular user extension is incorporated in an implementation or even
standardized?  The read-macro issues in Dick Waters' new pretty
printer are a good example; he uses #" as a read macro in a
particularly elegant way -and- this in conflict with currect practice
in KCL, which uses #" for pathnames.

At the least we need to officially recognize this problem and set some
guidelines for oursevles.