Is it a list ?

[Johan Garpendahl]

Hello Zoltan!

This is a slightly simplified explaination.

I think each element in a list has two parts.
The first part contains a pointer to the actual element and the other
part points to the next element in the list.
In a simple list, the first part points a number. In a less simple
list, the first element could point to another list.

At the end of a list, you usually want to put an emty list element.
That could be represented by a null pointer.

To modify your example, that would be:

1> X = [1,2|[]].
[1,2]

That is, [1,2|[]] and [1,2] is exactly the same thing.
[1,2] is somewhat shorter to write.

Hope I have explained more than I have confused.

Regards,

	Johan



>>>>> "Zoltan" == Zoltan Peter Toth <Zoltan.Toth@REDACTED> writes:

Zoltan> Hi !  I've made a little test in the Erlang machine:

Zoltan> 1> X = [1|2].
Zoltan> [1|2]

Zoltan> Now, my big question is, WHAT an object is X ?

Zoltan> 2> is_list(X).
Zoltan> true

Zoltan> So, it is a list, but not a well formed one:

Zoltan> 3> list_to_tuple(X).

Zoltan> =ERROR REPORT==== 10-Jul-2003::11:09:15 === Error in process
Zoltan> <0.26.0> with exit value:
Zoltan> {badarg,[{erlang,list_to_tuple,[[1|2]]},{erl_eval,expr,3},{erl_eval,exprs,4},{shell,eval_loop,2}]}
Zoltan> ** exited: {badarg,[{erlang,list_to_tuple,[[1|2]]},
Zoltan> {erl_eval,expr,3}, {erl_eval,exprs,4}, {shell,eval_loop,2}]}
Zoltan> **

Zoltan> 9> length(X).

Zoltan> =ERROR REPORT==== 10-Jul-2003::11:12:42 === Error in process
Zoltan> <0.39.0> with exit value:
Zoltan> {badarg,[{erlang,length,[[1|2]]},{erl_eval,expr,3},{erl_eval,exprs,4},{shell,eval_loop,2}]}
Zoltan> ** exited: {badarg,[{erlang,length,[[1|2]]},
Zoltan> {erl_eval,expr,3}, {erl_eval,exprs,4}, {shell,eval_loop,2}]}
Zoltan> **

Zoltan> ... so what is the structure and what are the elements and the
Zoltan> length of this weird list ?  Thanks for any answer, Zoltan