CODEWITHSUNDEEP
listlispcommon-lispappend
Roger Nash
Roger Nash

Reputation: 61

Implementing basic library functions in LISP (manually)

Is there any way by which I can define functions my_list, my_cons, my_append which perform similar function as list, cons and append respectively?

Otherwise where can I find the implementation of these functions?

Thanks

Upvotes: 2

Views: 284

Answers (2)

Alexandre Deschamps
Alexandre Deschamps

Reputation: 1238

For my_list and my_append, the solutions are:

(defun my_list (&rest arguments)
    `(,@arguments)
)

(defun my_append (a_list an_item)
    `(,@a_list ,an_item)
)

(my_append (my_list 'a 'b 'c) 'd)

I'm probably wrong but I dont know any alternative method to make pairs, so an alternative to cons do not seems possible. Still, I'm quite new to the LISP world.

Upvotes: 2

The Archetypal Paul
The Archetypal Paul

Reputation: 41769

If you want your lists to be the same as the onces native to your application, You have to start with some primitive to construct a cons, probably cons or dotted-pair, and something to pull a cons cell apart (car, cadr). The others can be build from that.

If you want to re-implement things that are functionally (pun intended) equivalent, see http://en.wikipedia.org/wiki/Cons#Not_technically_fundamental

Upvotes: 0

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