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

[Rick Pettit]

Technically Erlang does have arrays—see “erl -man array” for details.

-Rick

> On Jan 25, 2015, at 4:42 PM, Christopher Vance <cjsvance@REDACTED> wrote:
> 
> 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 <mailto: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 <mailto: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 <mailto: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 <mailto: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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> Christopher Vance
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