[Rd] new bquote feature splice does not address a common LISP @ use case?

[Jan Gorecki]

Dear R-devel,

There is a new feature in R-devel, which explicitly refers to LISP @
operator for splicing.

> The backquote function bquote() has a new argument splice to enable splicing a computed list of values into an expression, like ,@ in LISP's backquote.

Although the most upvoted SO question asking for exactly LISP's @
functionality in R doesn't seems to be addressed by this new feature.

Is it possible to use new splice feature to create `6 - 5 + 4`
expression rather than `6 - (5 + 4)`?

b = quote(5+4)
b
#5 + 4
c = bquote(6-.(b))
c
#6 - (5 + 4)
d = bquote(6-..(b), splice=TRUE)
d
#6 - (5 + 4)

There is corresponding LISP code provided

CL-USER>
(setf b `(5 + 4))
(5 + 4)
CL-USER>
(setf c `(6 - , using b))
(6 - 5 + 4)
CL-USER>
(setf c-non-spliced `(6 - ,b))
(6 - (5 + 4))
CL-USER>

Thanks,
Jan Gorecki