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Re: Erlang: An Introduction to Records

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Re: Erlang: An Introduction to Records

Josef — Fri, 12 Mar 2010 07:08:44 -0000

Thanks!
The rather light green on the grey background made it very difficult to see the difference between () and {}. It would help it the contrast was increased.

Re: Erlang: An Introduction to Records

Brainiac 5 — Fri, 08 Jan 2010 20:26:09 -0000

Thanks, very precise info just what I was looking for. A brief contrasting vs. ets, dicts and maybe even Mnesia might make for a great extension to this article.

Re: Erlang: An Introduction to Records

vladev — Tue, 01 Dec 2009 15:38:53 -0000

Hi, great post.

You have a slight mistake thought:

"Since Erlang is side-effect free state cannot be kept globally."
What I think you meant was that Erlang is a functional language. Functional languages don't have state. Imperative do.

Erlang is not side-effect free language. Printing to the console is not a side-effect free operation and you can do it from virtually everywhere in Erlang. A side effect free language would be useless - you won't be able to communicate with anything (terminal, socket, etc.). Haskell can be thought of being a side-effect free, where side effects are controller by monads.

Regards

Re: Erlang: An Introduction to Records

Alain O'Dea — Thu, 19 Jun 2008 11:42:36 -0000

Good article. Thank you for the concise and clear description of Erlang's records mechanism. It answered a few questions I had about guards,

Re: Erlang: An Introduction to Records

Robert Virding — Sun, 15 Jun 2008 16:19:55 -0000

Records were never intended to be anything else other than providing named fields for tuples. In this respect they *are* like C structs and should not be confused with associative arrays, use dict, orddict or gb_trees for that. Or ETS.

Re: Erlang: An Introduction to Records

Jesse — Sun, 15 Jun 2008 15:31:17 -0000

Gleb,

Good catch. And thanks for pointing to proplists, I didn't know about them.

Re: Erlang: An Introduction to Records

Jesse — Sun, 15 Jun 2008 15:23:03 -0000

website,

I'm not sure if you're a real person or a spam bot, but by "a la PHP, Ruby, or Python" I meant as a first-order construct. I'll reword it so it's less ambiguous.

Re: Erlang: An Introduction to Records

website design — Sun, 15 Jun 2008 13:44:32 -0000

> so creating associative arrays a la PHP, Ruby, or Python is an impossibility. ... some more bloggery ... > If you want to to add and remove fields on the fly, or if you don't know what fields you'll have until runtime, you should use [dicts](http://www.erlang.org/doc/m... rather than records. Huh?

Re: Erlang: An Introduction to Records

Gleb Peregud — Sun, 15 Jun 2008 09:46:12 -0000

Sorry for double posting.

> Perhaps a subset of the first, records are also used to keep track of configurable options.

Yes, records may be used for this. But sometimes proplists are better choice, take a look at http://www.erlang.org/doc/m...

> Property lists are useful for representing inherited properties, such as
> options passed to a function where a user may specify options overriding
> the default settings, object properties, annotations, etc.

Re: Erlang: An Introduction to Records

Gleb Peregud — Sun, 15 Jun 2008 09:41:14 -0000

In the "Updating Records" there is one issue.

Opts = #server_opts{port=80, ip="192.168.0.1"},
NewOpts = Opts#{port=7000}.

should look like this:

Opts = #server_opts{port=80, ip="192.168.0.1"},
NewOpts = Opts#server_opts{port=7000}.