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| Guest |
 Posted: Fri Sep 18, 2009 7:01 pm |
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Guest
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Hello,
I would like to match entries in an ets table based on some fields of
records, as in the example module below.
When using the _='_' form for defining the "don't care" record fields,
Dialyzer emits the following (reasonable) warnings:
rec.erl:6: Function p/0 has no local return
rec.erl:9: Record construction #rec{x::1,y::'_',z::'_'} violates the
declared type for #rec{}
With multiple functions and modules, the no local return causes an an
avalanche of further no local return's and never called's.
Of course I could redefine the field types as {x::integer()|'_',
y::integer()|'_', z::integer()|'_'} but I would prefer another match
syntax or Dialyzer directive if available. So what choices do I have?
Best Regards,
Zoltan.
----------------------
-module(rec).
-export([p/0]).
-record(rec, {x::integer(), y::integer(), z::integer()}).
p() ->
ets:new(table, [named_table, {keypos, #rec.x}]),
ets:insert(table, [#rec{x=1,y=2,z=3}, #rec{x=4,y=5,z=6}]),
ets:match_object(table, #rec{x=1, _='_'}).
________________________________________________________________
erlang-questions mailing list. See http://www.erlang.org/faq.html
erlang-questions (at) erlang.org
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| warezio |
| Posted: Fri Sep 18, 2009 7:10 pm |
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User
Joined: 05 May 2007
Posts: 107
Location: Yahoo
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On Fri, 18 Sep 2009, Zoltan Lajos Kis wrote:
> Hello,
>
> I would like to match entries in an ets table based on some fields of
> records, as in the example module below.
> When using the _='_' form for defining the "don't care" record fields,
> Dialyzer emits the following (reasonable) warnings:
>
> rec.erl:6: Function p/0 has no local return
> rec.erl:9: Record construction #rec{x::1,y::'_',z::'_'} violates the
> declared type for #rec{}
>
> With multiple functions and modules, the no local return causes an an
> avalanche of further no local return's and never called's.
>
> Of course I could redefine the field types as {x::integer()|'_',
> y::integer()|'_', z::integer()|'_'} but I would prefer another match
> syntax or Dialyzer directive if available. So what choices do I have?
I've had this problem constantly. I've moved away from relaxing the type
specification in the record, and towards using setelement/3 to hide from
the dialyzer. It helps that when using mnesia you get
mnesia:table_info (Table, wild_pattern) to initialize the record.
Cheers,
-- p
________________________________________________________________
erlang-questions mailing list. See http://www.erlang.org/faq.html
erlang-questions (at) erlang.org
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| Guest |
| Posted: Fri Sep 18, 2009 7:17 pm |
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Guest
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Zoltan Lajos Kis wrote:
> Hello,
>
> I would like to match entries in an ets table based on some fields of
> records, as in the example module below.
> When using the _='_' form for defining the "don't care" record fields,
> Dialyzer emits the following (reasonable) warnings:
>
> rec.erl:6: Function p/0 has no local return
> rec.erl:9: Record construction #rec{x::1,y::'_',z::'_'} violates the
> declared type for #rec{}
>
> With multiple functions and modules, the no local return causes an an
> avalanche of further no local return's and never called's.
>
> Of course I could redefine the field types as {x::integer()|'_',
> y::integer()|'_', z::integer()|'_'} but I would prefer another match
> syntax or Dialyzer directive if available. So what choices do I have?
From the options you mention, the best is to use a more relaxed type
declaration in the record fields of interest.
IMO, it was a design mistake to use a perfectly valid Erlang term
(namely the atom '_') as a symbol with a different meaning in match
specifications.
Kostis
> ----------------------
>
> -module(rec).
> -export([p/0]).
>
> -record(rec, {x::integer(), y::integer(), z::integer()}).
>
> p() ->
> ets:new(table, [named_table, {keypos, #rec.x}]),
> ets:insert(table, [#rec{x=1,y=2,z=3}, #rec{x=4,y=5,z=6}]),
> ets:match_object(table, #rec{x=1, _='_'}).
>
> ________________________________________________________________
> erlang-questions mailing list. See http://www.erlang.org/faq.html
> erlang-questions (at) erlang.org
________________________________________________________________
erlang-questions mailing list. See http://www.erlang.org/faq.html
erlang-questions (at) erlang.org
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| Guest |
| Posted: Fri Sep 18, 2009 7:26 pm |
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Guest
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Kostis Sagonas wrote:
> Zoltan Lajos Kis wrote:
>> Hello,
>>
>> I would like to match entries in an ets table based on some fields of
>> records, as in the example module below.
>> When using the _='_' form for defining the "don't care" record
>> fields, Dialyzer emits the following (reasonable) warnings:
>>
>> rec.erl:6: Function p/0 has no local return
>> rec.erl:9: Record construction #rec{x::1,y::'_',z::'_'} violates the
>> declared type for #rec{}
>>
>> With multiple functions and modules, the no local return causes an an
>> avalanche of further no local return's and never called's.
>>
>> Of course I could redefine the field types as {x::integer()|'_',
>> y::integer()|'_', z::integer()|'_'} but I would prefer another match
>> syntax or Dialyzer directive if available. So what choices do I have?
>
> From the options you mention, the best is to use a more relaxed type
> declaration in the record fields of interest.
>
> IMO, it was a design mistake to use a perfectly valid Erlang term
> (namely the atom '_') as a symbol with a different meaning in match
> specifications.
>
> Kostis
I have to agree. For some reason I believed '_' and '$1' are merely
syntactic sugar, and they are magically transformed into some sort of
match specifications. I had some fun trying to figure out how to make
the compiler accept expressions like #rec{x=1, _='_'} = '$1' until I
realized these really are just atoms 
>
>> ----------------------
>>
>> -module(rec).
>> -export([p/0]).
>>
>> -record(rec, {x::integer(), y::integer(), z::integer()}).
>>
>> p() ->
>> ets:new(table, [named_table, {keypos, #rec.x}]),
>> ets:insert(table, [#rec{x=1,y=2,z=3}, #rec{x=4,y=5,z=6}]),
>> ets:match_object(table, #rec{x=1, _='_'}).
>>
>> ________________________________________________________________
>> erlang-questions mailing list. See http://www.erlang.org/faq.html
>> erlang-questions (at) erlang.org
>
________________________________________________________________
erlang-questions mailing list. See http://www.erlang.org/faq.html
erlang-questions (at) erlang.org
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| wuji |
| Posted: Tue Aug 28, 2012 7:39 am |
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