[gambit-list] (no subject)

REPLeffect repleffect at gmail.com
Sat Oct 6 23:21:02 EDT 2012

What would it take to expose a procedure in the interpreter for
completing symbols in the symbol table.  What I mean is, I'd like a
scheme procedure I could call with a string representing either a full
or a partial symbol, and the procedure would give me back a list of
the possible completions for currently defined symbols.

Essentially I want a procedure that does what the tab completion in
the interpreter's REPL does.

I'm using the partially-implemented swank backend that James Long was
working on a while back, and I found these procedures that Marc posted
to the list back in March of '09:

 (define (symbol-table->list st)

    (define (symbol-chain s syms)
      (let loop ((s s) (syms syms))
        (if (symbol? s)
            (loop (##vector-ref s 2) (cons s syms))

    (let loop ((lst (vector->list st)) (syms '()))
      (if (pair? lst)
          (loop (cdr lst) (symbol-chain (car lst) syms))
          (reverse syms))))

 (define (interned-symbols)
    (symbol-table->list (##symbol-table)))

 (pp (length (interned-symbols)))

(that was from this post:

>From that I cobbled together a very inefficient hash-table-based tab
completion (especially inefficient because of duplicating the entire
symbol table in a hash table, one key per symbol).  I realize this is
a complete kludge and wastes tremendous amounts of memory.  I'd like
to do it right and just query the symbol table itself, since the data
is obviously already there.

I found the complete_word(), lineeditor_word_completion(), and
visit_symbol() functions in os_tty.c, and I'm sure that the solution
is to write a similar set of C functions to act as a scheme interface
to do what I want.  However, I suspect I don't understand the code
well enough at this point to do that correctly.

I'd be willing to give it a shot if I thought I had a sufficient
quantity of tips on how to get it done (I started to say 'pointers' on
how to get it done, but I suspected that would only lead to a long
string of programmer jokes that might derail this thread :-D ).

It seems to me that this would be a good thing to have available for
any application that might embed Gambit and/or communicate with a
process running the Gambit interpreter.  I don't think the
applicability would be in any way limited to slime/swank (though,
admittedly, that is my primary motivation for having it).


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