Re: Is this a bug in while-let or do I missunderstand it?

[Andreas Schwab]

On Nov 09 2024, Eli Zaretskii wrote:

>>       It can be convenient to bind variables in conjunction with using a
>>    conditional.  It's often the case that you compute a value, and then
>>    want to do something with that value if it's non-‘nil’.  The
>>    straightforward way to do that is to just write, for instance:
>>    
>>         (let ((result1 (do-computation)))
>>           (when result1
>>             (let ((result2 (do-more result1)))
>>               (when result2
>>                 (do-something result2)))))
>> 
>>       Since this is a very common pattern, Emacs provides a number of
>>    macros to make this easier and more readable.  The above can be written
>>    the following way instead:
>> 
>> ... following the various with various FOO-let forms, ending with
>> while-let.
>
> The above description actually supports what Yuri was saying, not what
> Arthur and you expect.

The description only talks about when, where the condition is only
evaluated once not matter what.  If you replace when with while you have
a very different situation.

-- 
Andreas Schwab, schwab@linux-m68k.org
GPG Key fingerprint = 7578 EB47 D4E5 4D69 2510  2552 DF73 E780 A9DA AEC1
"And now for something completely different."