[erlang-questions] Where is an ets guide?

Bob Ippolito <>
Fri Sep 22 01:21:26 CEST 2006


On 9/21/06, Jeff Crane <> wrote:
> I would like to find an ets usage guide?
>
>
> I had to type in "ets:new erlang" to Google just to
> come up with a half tutorial that just raises more
> questions.
>
> http://schemecookbook.org/Erlang/HashChapter
> ---
> dict provides a simple dictionary implementation, in
> which values (of any Erlang type) can be stored and
> accessed by keys (Erlang terms). ets has a similar
> interface, but is designed for dealing with vast
> quantities of
> data.
> ---
> What does that mean? They are the same, but not, and
> one is designed for dealing with lots of data, and
> dict is for something else entirely, like making
> toast?

I'm new to Erlang, but I didn't have any problems figuring it out from
the documentation. I don't know why you're looking at older docs from
somewhere other than erlang.org though? From erlang.org, click
"documentation" on the left, then the first link "Erlang/OTP R11B
documentation".. which takes you to the current docs here:
http://erlang.org/doc/doc-5.5.1/doc/

To find docs for a module it'll be under one of the Applications on
the menu bar in the left. It's anyone's guess which application a
given module will be in, but I would look in stdlib first, then
kernel. ets is in stdlib.

> look around and HOPE new/2 is the correct choice to
> start...
>
> ets:new(Name,Options) -> tid()
>
> so I type
>
> ets:new(mytable,[]).
> 16 % that's a tid!

Identifiers are supposed to be opaque.. just like the internal
representation of dict, etc.

> ets:insert(mytable,{1,"first"}).
> % Nope...wtf?

mytable isn't the Tid, and you didn't ask for a named table.

> MyTable2 = ets:new(mytable2,[]).
> 19 % that's a tid!
>
> ets:insert(MyTable2,{2,"second"}).
> % true? Um, I'm lost.

How lost could you be? It says very specifically that it always
returns true. What else would you want it to return?

> What's the point of the name atom?

It helps to read *all* of the docs for a function. There's a
named_table option, which lets you specify the Tid as an atom:

* named_table  If this option is present, the name Name is associated
with the table identifier. The name can then be used instead of the
table identifier in subsequent operations.

> Better yet, where's a halfway decent guide to ETS?

The docs are pretty sufficient, if you read them.

-bob



More information about the erlang-questions mailing list