Sharp-backquote is defined by rutils.  It has nothing to do with backquote.

By analogy with sharp-quote being a quote of a functional form, sharp-backquote produces functions that you don't wish to name whose parameters you also don't wish to name other than by % and %% being two positional parameters. Clojure has a similar concept.
James Lawrence pointed out that Clojure gets use/mention similarly wrong - it fails to recognize when the % symbol has been quoted and will blindly stuff in the equivalent of a gensym in a not-for-evaluation position.

On Sat, May 10, 2014 at 7:54 PM, Faré <> wrote:
On Sat, May 10, 2014 at 4:03 PM, Douglas Katzman <> wrote:
> Looks like we're just not getting the patch right, and that as a minor
> hindrance, changing a function that was set-macro-character'd into a named
> readtable doesn't force recompilation of files that use the readtable.  So
> in part my testing has been bogus.
> To bring you up to speed: nothing has changed in SBCL in relation to
> backquote yet, though it might. I proactively suggested to the rutils
> maintainer that he could eliminate the assumption that SUBST was a
> "reasonable" way to perform alpha conversion of a lambda expression by
> instead using sb-walker in sbcl. Then I saw that my first patch - which I
> think was correct as it stood - was inconsistent with the behavior for other
> lisps.  #` is supposed to treat #`((foo) (bar)) as (progn (foo) (bar)) which
> I failed to realize.
> I'll try one more time and make sure a forced recompile works.
Wait, where is that sharsign backquote thing defined???
CLHS 2.4.8 says that it's undefined.

If there's a standard for it somewhere, I'd like to know about it,
so I may implement it in fare-quasiquote.

And yes, SUBST is a very bad way of doing alpha conversion: it goes
not only under BACKQUOTE, but under QUOTE — but not under #(), and
maybe maybe not under `#(). In other words, it SUCKS, and programs
that use it are probably buggy.

—♯ƒ • François-René ÐVB Rideau •Reflection&Cybernethics•
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from them. But when you've robbed a man of everything he's no longer in
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