RE: Visible Hash-Tables

[Barry Margolin <barmar@Think.COM>]

    Date: Tue, 17 May 88 10:05 EDT
    From: ELIOT@cs.umass.edu

    Both INSPECT and DESCRIBE are "standard" CLtL functions.  The results
    are not READable, but the original question was for a way to allow
    students to look inside hash-tables.  INSPECT may be too complex
    for students (I don't use INSPECT) but DESCRIBE should not be.
    However, CLtL does not specify that either of these functions will
    show you the content of Hash-Tables.  Would it be resonable to
    specify for each data type what is the minimal information that
    these functions must show?  Better still for DESCRIBE, at least,
    would be a portable public domain implementation.

Until we define CL functions for examining defstruct structures (e.g. a
function that takes a structure name and returns a list of slot accessor
functions) it will not be possible to write a portable DESCRIBE that can
tell you the contents of a structure.  Also, there are no accessors
at all for some other types, such as RANDOM-STATE and HASH-TABLE (and
this is the one that prompted this discussion).

One of the reasons that DESCRIBE is part of the standard is because it
is impossible to write a useful version of it using the existing
accessors.

                                                barmar