Re: Idiomatic way to avoid unused lexical variable in ‘dotimes’ or ‘dolist’?

[Tim Landscheidt <tim@tim-landscheidt.de>]

(anonymous) wrote:

>>> 1. Is there an idiom in Emacs Lisp for writing this that
>>>    eliminates this warning?

>>     (dotimes (_ 100)
>>       (insert "I will not obey absurd orders\n"))

>> Or any other var name that starts with an underscore.

> Thank you.  I have not been able to find this documented anywhere (that
> is, that lexical variables whose names begin with an underscore are not
> flagged with a warning message if they are not referenced).  This
> appears to be true with, for example, ‘let’ expressions, also.

It is mentioned in the GNU Emacs Lisp Reference Manual (C-h
i g (elisp) RET) in the node "Converting to Lexical
Binding":

| […]

|    A warning about an unused variable may be a good hint that the
| variable was intended to be dynamically scoped (because it is actually
| used, but in another function), but it may also be an indication that
| the variable is simply really not used and could simply be removed.  So
| you need to find out which case it is, and based on that, either add a
| ‘defvar’ or remove the variable altogether.  If removal is not possible
| or not desirable (typically because it is a formal argument and that we
| cannot or don’t want to change all the callers), you can also add a
| leading underscore to the variable’s name to indicate to the compiler
| that this is a variable known not to be used.)

| […]

Tim