[slime-devel] Re: REPL-specific printer control variables
nikodemus at random-state.net
Wed May 24 07:25:45 UTC 2006
"Robert J. Macomber" <slime at rojoma.com> writes:
> This patch adds two variables to swank: *listener-print-level* and
> *listener-print-length*, analogous to the standard Lisp variables
> *print-level* and *print-length*, used to control how much of a form's
> return values get printed at the REPL but not of things printed
> directly by user code. If they're bound (by default, they aren't)
> then swank uses them when preparing the presentation of an
> evaluation's result for sending to Emacs. When they're unbound, the
> values of the standard CL depth and length variables instead.
While I symphatize with the motivation, I also strongly disagree with
this patch on two grounds:
1. *PRINT-LEVEL* &co are the right tools to use for affecting the
REPL. If your code assumes magic values of *PRINT-LEVEL* it is
more-or-less broken, and should bind them explicitly, for which
you will find WITH-STANDARD-IO-SYNTAX convenient.
2. If this really really must go in, please let us make it
*PRESENTATION-PRINT-ALIST* instead, and use a PROGV:
(let ((bindings (reverse *listener-print-alist*)))
(progv (mapcar #'car bindings) (mapcar #'cdr bindings)
This way when someone needs *PRINT-RADIX* or similar they don't have
to add and document another variable.
-- Nikodemus Schemer: "Buddha is small, clean, and serious."
Lispnik: "Buddha is big, has hairy armpits, and laughs."
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