Re: multiple read-time conditionals, puzzlement

Would someone mind quoting “chapter and verse”? 

Somehow, even those of us with decades of Common Lisp experience, all trying to follow the drama of the X3J13 committee, a bunch of us “missed the memo” about this convenient, allegedly legal, but “buyer beware” syntax. 

Yes, I absolutely hate 
     #+foo :keyword #+foo argument too. 

--Tim

> On Mar 13, 2023, at 14:00, Robert Goldman <[email protected]> wrote:
> 
> 
> On 13 Mar 2023, at 12:42, Ron Garret wrote:
> 
> Oh, forgot to add...
> 
> On Mar 13, 2023, at 10:20 AM, Arthur Cater <[email protected]> wrote:
> 
> It never previously occurred to me that read time conditionals could be nested.
> 
> Just because you can do something doesn't mean you should.
> 
> rg
> 
> I was surprised myself to see
> 
> #+foo #+foo
> used to make two s-expressions (in)visible in the presence (absence) of the :foo feature. But it's clearly dictated by the spec, and is often handy when, for example one might want to have something conditionally in a property list
> 
> (list :prop1 12
>       #+foo #+foo
>       :foo 'bar)
> In my opinion, that's clearer than
> 
> (list :prop1 12
>       #+foo :foo #+foo 'bar)
> which obscures reading this as a property list and obscures the fact that the two elements of the list are going to be swapped in or out based on a single feature.
> 
> (append (list :prop 12) #+foo (list :foo 'bar) )
> is not an alternative particularly pleasing to me, but YMMV. It's certainly very busy.