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Re: Improving aesthetics & readability of backquote
From: |
Stefan Monnier |
Subject: |
Re: Improving aesthetics & readability of backquote |
Date: |
Sun, 19 May 2019 23:38:38 -0400 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/27.0.50 (gnu/linux) |
> Then it would be a case of augmenting the "unquote" ,VAR and "splice" ,@VAR
> reader constructs:
>
> (quoteval (1 2 (unquote a) 5 (splice b) 8 ))
> -> (1 2 (3 4) 5 6 7 8)
You'd feel quite at home in Scheme where the reader's
'E => (quote E)
is complemented by
`E => (quasiquote E)
,E => (unquote E)
,@E => (unquote-splicing E)
Elisp doesn't have that, mostly for historical reasons, I think.
I haven't been able to confirm it, but I believe the road looked like:
the Elisp reader originally only had the `quote` special element and
since people don't like to write (backquote (foo bar (unquote baz))),
they started writing (` (foo bar (, baz))) which was at least vaguely
reminiscent of the "normal" backquote/unquote used in other Lisps.
This is the "old-style" quotes. When the new-style quotes were added
to the reader (those that look like regular Lisp) it was natural to map
`E => (` E)
so that the existing definition of the ` macro worked both with the new
and with the old syntax.
Stefan