[erlang-questions] Local namespaces in case/try

Ivan Uemlianin <>
Tue Jul 10 12:20:44 CEST 2012


On 10/07/2012 11:10, Dmitry Groshev wrote:
> Ivan,
>
> There is a concept called "lexical scoping" — it means that some lexical
> constructs have a local namespace. In that example I would expect that
> all variables that were introduced inside case statement (Error/Result)
> won't be bound after the statement.

In erlang it seems that they are bound:
http://www.erlang.org/course/advanced.html#scope
http://www.erlang.org/doc/reference_manual/expressions.html#id75881


> ... I'm sorry
> but I can't see why do you think that that values should be identical.

I am only a beginner.

Ivan

>
> On Tuesday, July 10, 2012 1:54:11 PM UTC+4, Ivan Uemlianin wrote:
>
>      > On 07/10/2012 10:43 AM, Dmitry Groshev wrote:
>      > case do_something() of
>      >      {ok, Result} -> Result;
>      >      {error, Error} -> Error
>      > end,
>      > case do_another() of
>      >      {ok, Result} -> Result;
>      >      {error, Error} -> Error
>      > end,
>      >
>      > Result and Error are bound in first case and we will probably have a
>      > match failure in second one. Compiler warns about this, but it's
>     still
>      > very unwieldy to fix it with names like Error1, Error2, etc.
>
>     Are you expecting that the "Result" variable returned from do_another()
>     should have the same value as the "Result" returned from
>     do_something()?
>        (and likewise for Error.)
>
>     If so, I don't see why you would get a match failure: e.g., you surely
>     wouldn't get a match failure if do_something() and do_another() both
>     returned {ok, 5}?
>
>     If not, yes you will get match failures.
>
>     To this naive observer, the code looks like the "Result"s (and the
>     "Errors"s) are expected to be identical.
>
>     Best wishes
>
>     Ivan
>
>
>     --
>     ============================================================
>     Ivan A. Uemlianin PhD
>     Llaisdy
>     Speech Technology Research and Development
>
>      <mailto:>
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-- 
============================================================
Ivan A. Uemlianin PhD
Llaisdy
Speech Technology Research and Development

                     
                      www.llaisdy.com
                          llaisdy.wordpress.com
               github.com/llaisdy
                      www.linkedin.com/in/ivanuemlianin

               "hilaritas excessum habere nequit"
                  (Spinoza, Ethica, IV, XLII)
============================================================





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