Indexing a vector

Indexing a vector

[Nordlöw]

How do index an element in a vector? nth() works only for lists.

:(... 0 '[1 2])

Why on earth isn't such a basic operator compatible with both lists
and vectors (sequences)?

/Nordlöw

RE: Indexing a vector

[Drew Adams]

> How do index an element in a vector? nth() works only for lists.
> 
> :(... 0 '[1 2])
> 
> Why on earth isn't such a basic operator compatible with both lists
> and vectors (sequences)?

`elt'

C-h i, choose Elisp manual, g Sequence Functions

Re: Indexing a vector

[Juanma Barranquero]

On Wed, Sep 10, 2008 at 16:53, Nordlöw <per.nordlow@gmail.com> wrote:

> How do index an element in a vector?

(aref [a b c d] 2)  =>  c

> nth() works only for lists.

Yes, `nth' is a list operation.

> Why on earth isn't such a basic operator compatible with both lists
> and vectors (sequences)?

Because it is a list operation. For the generic sequence operator, try `elt':

  (elt '(a b c d) 2) => c
  (elt [a b c d] 2)  => c
  (elt "abcd" 2) => 99

 Juanma

Re: Indexing a vector

[Ted Zlatanov]

On Wed, 10 Sep 2008 07:53:04 -0700 (PDT) Nordlöw <per.nordlow@gmail.com> wrote: 

N> How do index an element in a vector? nth() works only for lists.
N> :(... 0 '[1 2])

N> Why on earth isn't such a basic operator compatible with both lists
N> and vectors (sequences)?

The Emacs Lisp manual (chapter 6) covers this.  A vector is an array
which is a sequence, but not a list (so you can use the `elt' function
in addition to `aref' to look up elements).  `nth' works only on lists.

Ted