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Applying print-length to (length string) is suboptimal.

From: Alan Mackenzie
Subject: Applying print-length to (length string) is suboptimal.
Date: Sun, 17 Sep 2023 19:57:07 +0000

Hello, Emacs.

Also with reference to bug #65680.

In cl-print-object (lisp/emacs-lisp/cl-print.el), the version for
strings, print-length is taken as a bound on the length of the string to
be printed.


The whole idea of print-length (and print-level) is, as far as I can make
out, to prevent infinite printing when there's a circular list, for
example.  This cannot occur for strings.

This use of print-length is relatively recent, originating in this

    commit 8a7620955b4d859caecd9a5dc9f2a986baf994fd
    Author: Gemini Lasswell <gazally@runbox.com>
    Date:   Fri Jun 15 10:26:13 2018 -0700

        Add methods for strings to cl-print

print-length is not used in the function prin1 (as contrasted with

The problem with using print-length for the max. string length is that it
is not designed for this.  When print-length is, say, 50, almost any list
or vector can be printed in full, going up to several hundred printed
characters.  With a string, the string gets rudely truncated at a mere 50
characters, which is rarely wanted.  This is a problem with the error
message at the top of a backtrace, where cl-print-string-with-limit
limits print-length to a maximum of 50 (See bug #65680).

What do people think of removing this observance of print-length from the
string version of cl-print-object?

Alan Mackenzie (Nuremberg, Germany).

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