,@ v.s. ,.

I’m surprised that I didn’t know about the ,. construct in Common Lisp’s backquote syntax. ┬áIt is equivalent to ,@ except that it licenses the implementation to destructively modified the tail of the list being inlined.

cl-user> (defparameter *x* '(1 2 3))
*x*
cl-user> *x*
(1 2 3)
cl-user> `(a b ,@*x* c d)
(a b 1 2 3 c d)
cl-user> *x*
(1 2 3)
cl-user> `(a b ,.*x* c d)
(a b 1 2 3 c d)
cl-user> *x*
(1 2 3 c d)
cl-user>

2 thoughts on “,@ v.s. ,.

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