20bits - Latest Comments in Erlang: An Introduction to Records | 20bits

Re: Erlang: An Introduction to Records | 20bits

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 | 20bits

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 | 20bits

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 | 20bits

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 | 20bits

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/man/dict.html) rather than records. Huh?

Re: Erlang: An Introduction to Records | 20bits

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/man/proplists.html:

> 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 | 20bits

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}.