[erlang-questions] lists:concat with non-string sublists

James Aimonetti <>
Tue May 22 19:27:32 CEST 2012


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According to the docs[1], lists:concat/1 converts the elements in the
list to their string representation. The spec for Thing being atom() |
integer() | float() | string().

However, in the actual implementation in lists.erl, the is_list/1
guard is used in thing_to_list/1, not a more specific check that the
list is a string().

So, according to the docs, I would expect:

> lists:concat([[{foo, 123}], [{bar, 234}]]).

to fail. It doesn't, and returns [{foo, 123}, {bar,234}]. Reading the
implementation of concat/1 its easy to see why this works.

My question is, should the docs be updated to allow Thing to be a list
of any term so Dialyzer won't issue an error when using sub-lists with
tuples (in my case, the result of an ets:match/2), or should
thing_to_list/1 do more inspection of a list element?

Thanks,

James

[1] http://www.erlang.org/doc/man/lists.html#concat-1
- -- 
James Aimonetti
Distributed Systems Engineer / DJ MC_

2600hz | http://2600hz.com
sip:
tel: 415.886.7905
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