(in-package :FOO)

[Vladimir Zolotykh]

Could you name reasons to write in-package the way as it
done in subject (beside personal preferences of course) ?
In ANSI compliant CL it seems has no effect whether :foo or
:FOO used. In CL with modern case mode such writing should
be less compatible. So when it could be useful ?

--
Vladimir Zolotykh

[Kaz Kylheku]

Both :foo and :FOO are two equally valid printed representations
of the same symbol, whose name is the string "FOO". Here are
some other possible representations:

'(:|FOO| :\F\Oo :\F\O\O)

On the other hand, (in-package :|foo|) is quite different.

In package naming, symbols are exploited for their name.
You could use a string instead, in which case you must
make it upper case to match the symbol name:

(in-package "FOO")