[Openmcl-devel] *default-external-format* and encoding and decoding strings.

[Ron Garret]

On Mar 7, 2016, at 2:37 PM, Dmitry Igrishin <dfigrish at gmail.com> wrote:

>> > (in-package :ccl)
>> >
>> > (let ((ccl::*warn-if-redefine-kernel* nil))
>> >   (defun lookup-character-encoding (name)
>> >     (gethash (or name *default-external-format*) *character-encodings*)))
>> 
>> I don't think I can apply this.
>> 
>> The issue is that nil is a valid character encoding name: it's a documented synonym for :iso-8859-1.
> 
> Just curious, why is so? Doesn't the "nil" means "unknown" or "false"? And if something that means
> the "default" is "unknown" or "false" should by treated as exceptional situation?

It’s to maintain backwards-compatibility with CCL before *default-external-format* was introduced, when :ISO-8859-1 was hard-coded as the default.  There was a big discussion over whether or not to change this, and *default-external-format* was introduced as a backwards-compatible compromise.

rg