2010/12/8 Peter Bex <[email protected]>:
> [...]
> I find this _very_ weird. It feels as if they made (+ (values 1 2 3))
> be identical to (+ 1 2 3) - sorry if that's a weird analogy, but it's
> exactly the same to my brain.
Hello,
to me the analogy seems quite well chosen. By the way, sometimes I
actually wonder whether splicing behaviour of multiple values in an
argument list wouldn't be a good idea, but I'm unsure.
> [...]
> Quasiquote itself is not allowed to have multiple arguments,
> which is also a bit inconsistant (but logical). Racket does allow
> multiple nested arguments to quasiquotes. I haven't been able to test
> with any other r6rs Scheme because Racket is the only one available in
> pkgsrc and I'm not willing to mess around with building one from source.
> Extra data points would be appreciated if someone else reading this
> happens to have another r6 implementation at hand.
> [...]
Here are the results with two other R6RS implementations:
Petite Chez Scheme 8.0:
> (let ([a 0] [b 1] [c 2])
(quasiquote ((unquote a b c))))
(0 1 2)
> (let ([a 0] [b 1] [c 2])
(quasiquote (unquote a b c)))
(unquote a b c)
> (let ([a 0] [b 1] [c 2])
(quasiquote (quasiquote (unquote a b c))))
`(unquote a b c)
> (let ([a 0] [b 1] [c 2])
(quasiquote (unquote a) (unquote b) (unquote c)))
Exception: invalid syntax (quasiquote (unquote a) (unquote b) (unquote c))
Ypsilon 0.9.6-update3
> (let ([a 0] [b 1] [c 2])
(quasiquote ((unquote a b c))))
(0 1 2)
> (let ([a 0] [b 1] [c 2])
(quasiquote (unquote a b c)))
error in quasiquote: unquote appear in bad context
> `(unquote a b c)
..."/dev/stdin" line 2
@ (unquote a b c)
..."/dev/stdin" line 2
> (let ([a 0] [b 1] [c 2])
(quasiquote (quasiquote (unquote a b c))))
`(unquote a b c)
> (let ([a 0] [b 1] [c 2])
(quasiquote (unquote a) (unquote b) (unquote c)))
0
I'd say, the behviour is not exactly consistent between
implementations.
Ciao,
Thomas
--
When C++ is your hammer, every problem looks like your thumb.
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