[erlang-questions] why do I see a message about area of a square

[Christopher Vance]

The argument is a tuple. Erlang does not have arrays; you have to decide
whether to use a list or a tuple.

On Mon, Jan 26, 2015 at 12:36 AM, Roelof Wobben <r.wobben@REDACTED> wrote:

>  Nope, Thanks for the patience with me.
>
> So area is the function with 1 argument a array with the shape and the
> parameters to calculate it.
>
> Roelof
>
>
>
> Hynek Vychodil schreef op 25-1-2015 om 14:23:
>
> Sorry, typo I mean area/1 and arity 1 because you have only one parameter.
>
> On Sun, Jan 25, 2015 at 1:24 PM, Roelof Wobben <r.wobben@REDACTED> wrote:
>
>>  Sorry, now im totally confused .
>>
>> where does the name array come from and why a arity 1 ?
>>
>> Roelof
>>
>>
>> Hynek Vychodil schreef op 25-1-2015 om 13:07:
>>
>> Hi,
>>
>>  You don't have any functions named square, circle or triangle. You have
>> only one function array/1 with four function clauses, the first for square,
>> the second for circle, the third for triangle and the fourth catch-all one.
>>
>>  Hynek
>>
>> On Sun, Jan 25, 2015 at 12:29 PM, Roelof Wobben <r.wobben@REDACTED> wrote:
>>
>>> Thanks,
>>>
>>> That error messages disappear.
>>>
>>> As I understand it right. The eror message is on all functions so on the
>>> square, circle and triangle functions.
>>> And if not so, why also not a error functions on the other two.
>>>
>>> Roelof
>>>
>>>
>>>
>>>
>>> Taavi Talvik schreef op 25-1-2015 om 12:22:
>>>
>>>  Until you export your functions, they remain local to
>>>> module. And compiler sees here, that they are not used
>>>> locally here.
>>>>
>>>> Try adding
>>>> -export([area/1]).
>>>>
>>>> best regards,
>>>> taavi
>>>> On 25 Jan 2015, at 13:12, Roelof Wobben <r.wobben@REDACTED> wrote:
>>>>
>>>>  Hello,
>>>>>
>>>>> I have this programm  :
>>>>>
>>>>> -module(shapes).
>>>>>
>>>>> -import(math, [sqrt/1]).
>>>>>
>>>>> area({square, Side}) ->
>>>>>    Side * Side ;
>>>>>
>>>>> area({circle, Radius}) ->
>>>>>    math:pi() * Radius * Radius;
>>>>>
>>>>> area({triangle, A, B, C}) ->
>>>>>    S = (A + B + C)/2,
>>>>>    math:sqrt(S*(S-A)*(S-B)*(S-C));
>>>>>
>>>>> area(Other) ->
>>>>>    {error, invalid_object}.
>>>>>
>>>>>
>>>>> As soon I as try to compile it , I see these messages :
>>>>>
>>>>>
>>>>> 6> c(shapes).
>>>>> shapes.erl:5: Warning: function area/1 is unused
>>>>> shapes.erl:15: Warning: variable 'Other' is unused
>>>>>
>>>>> Why does Erlang do this?
>>>>> On compile time you cannot see which functions are used and which not
>>>>> in my oponion.
>>>>>
>>>>> Roelof
>>>>>
>>>>>
>>>>> _______________________________________________
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>>>>>
>>>>
>>>>
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>>
>>
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>
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-- 
Christopher Vance
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