[erlang-questions] What's this mean:[1|1]?It's it a bug?

[Lukas Larsson]

On Wed, Jul 3, 2013 at 12:09 PM, Ivan Uemlianin <ivan@REDACTED> wrote:

> [1|1] is an "improper list", in other words, a list that doesn't end with
> an empty list [].  They're valid, but not terribly safe:
>
>   1> is_list([1|1]).
>   true
>   2> length([1|1]).
>   ** exception error: bad argument
>        in function  length/1
>           called as length([1|1])
>
> I don't know if there's any use for them.
>

It can be used to save two words of memory as [1|1] is two words but [1,1]
is four words. So if you are developing a highly optimized data structure
(like dict for instance) it is useful. Most people will however not need
this.

Lukas
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