[erlang-questions] Newbie Question about io:format

Dmytro Lytovchenko <>
Tue Feb 21 10:42:14 CET 2017


Because Erlang has no functions with variable amount of arguments (like for
example in printf C/C++), args to io:format are passed as a list. So
correct way to call it is:

io:format("Bla ~p~n", [Av1]).

Where ~p is to print any value, also there are more ways to format a value,
consult the documentation page at http://erlang.org/doc/man/io.html#fwrite-1

2017-02-21 10:15 GMT+01:00 Hakim Fajardo <>:

> First, thank you because this is a great resource.
>
> Second, I started writing basic programs every day to improve my Erlang
> coding. I wrote a simple program that calculates the average of a list of
> numbers. But I keep getting this error about io:format.
>
>
> prices([]) ->
>     [],
>     io:format("List is empty ~n");
>
> %% determine number of items in the list to calculate average%%
>
> prices(L) when is_list(L) ->
>   Size = length(L),
>   Sum1 = lists:sum(L),
>   Av1 = Sum1 / Size,
>   io:format("The average equals ~n", Av1).
>
>
> Then..
>
> Eshell V8.2  (abort with ^G)
> 1> L = [1,2,2,2,3,3,4].
> [1,2,2,2,3,3,4]
>
> 2> c(standev).
> {ok,standev}
>
> 3> standev:prices(L).
> ** exception error: bad argument
>      in function  io:format/3
>         called as io:format(<0.50.0>,"The average equals
> ~n",2.4285714285714284)
>
>
> Why am I getting '**exception error:'?
>
> Thank you, I hope this isn't too newbie a question.
>
>
>
>
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> 
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>
>
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