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<div class="moz-cite-prefix">Oke, then this is a working solution. <br>
<br>
-module(side_effects).<br>
<br>
-export([display_numbers/1]).<br>
<br>
%% display_numbers(N) displays the numbers from 1,2,...+N when N
is a non-negative integer and is even.<br>
%% It is not defined for other arguments.<br>
%% When N is a non-negative number, a helper function is called
so it prints out<br>
%% the numbers in the right order. This is a exercise from the
Erlang Programming book<br>
%% where I have to practice side-effects. <br>
display_numbers(Number) when is_integer(Number), Number > 0
-><br>
display_numbers_loop(0, Number ).<br>
<br>
%% When the control argument)(second argument) is equal to the
number <br>
%% the user has given, the end is reached and the last number is
printed<br>
display_numbers_loop(Number, Number) -><br>
ok;<br>
<br>
%% When the contro argument(second argument) is not equal to the
number<br>
%% and the Current number is even, <br>
%% The control argument is increased by one and the <br>
%% display_numbers_loop function is called again with the new
arguments. <br>
display_numbers_loop(Current, Number) when Current rem 2 == 0 ,
Current /= 0 -><br>
io:format("Number:~p~n",[Current]), <br>
display_numbers_loop(Current +1, Number );<br>
<br>
%% When the contro argument(second argument) is not equal to the
number<br>
%% and the Current number is not even, <br>
%% The control argument is increased by one and the <br>
%% display_numbers_loop function is called again with the new
arguments. <br>
display_numbers_loop(Current, Number) when Current rem 2 /= 0;
Current == 0 -><br>
display_numbers_loop(Current +1, Number ).<br>
<br>
Roelof<br>
<br>
<br>
<br>
Erik Søe Sørensen schreef op 12-2-2015 om 17:47:<br>
</div>
<blockquote
cite="mid:CAO1s=UUAiVyJM3rEiFf_tFsLj3URXKx9jsc3LqPYEFMWZWGRjA@mail.gmail.com"
type="cite">
<p dir="ltr">Not so odd - look at the next line, at what you're
telling it to print (it's not Current).</p>
<div class="gmail_quote">Den 12/02/2015 15.51 skrev "Roelof
Wobben" <<a moz-do-not-send="true"
href="mailto:r.wobben@home.nl">r.wobben@home.nl</a>>:<br
type="attribution">
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">Thanks ,<br>
<br>
Stupid mistake I had to use rem.<br>
<br>
Now i have this :<br>
<br>
-module(side_effects).<br>
<br>
-export([display_numbers/1]).<br>
<br>
%% display_numbers(N) displays the numbers from 1,2,...+N
when N is a non-negative integer.<br>
%% It is not defined for other arguments.<br>
%% When N is a non-negative number, a helper function is
called so it prints out<br>
%% the numbers in the right order. This is a exercise from
the Erlang Programming book<br>
%% where I have to practice side-effects.<br>
display_numbers(Number) when is_integer(Number), Number > 0
-><br>
display_numbers_loop(0, Number ).<br>
<br>
%% When the control argument)(second argument) is equal to
the number<br>
%% the user has given, the end is reached and the last number
is printed<br>
display_numbers_loop(Number, Number) -><br>
ok;<br>
<br>
%% When the contro argument(second argument) is not equal to
the number<br>
%% and the Current number is even,<br>
%% The control argument is increased by one and the<br>
%% display_numbers_loop function is called again with the new
arguments.<br>
display_numbers_loop(Current, Number) when Current rem 2 == 0
-><br>
io:format("Number:~p~n",[Current + 1]),<br>
display_numbers_loop(Current +1, Number );<br>
<br>
%% When the contro argument(second argument) is not equal to
the number<br>
%% and the Current number is not even,<br>
%% The control argument is increased by one and the<br>
%% display_numbers_loop function is called again with the new
arguments.<br>
display_numbers_loop(Current, Number) when Current rem 2 /= 0
-><br>
display_numbers_loop(Current +1, Number ).<br>
<br>
but now I see only the odd numbers which I find wierd because
I say when Current rem 2 ==0 and that true for even numbers.<br>
So then the io can be found.<br>
<br>
Roelof<br>
<br>
<br>
<br>
Bengt Kleberg schreef op 12-2-2015 om 15:38:<br>
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">
Have you tested<br>
Current / 2 == 0<br>
with some values for Current?<br>
It is only true when Current is 0.<br>
<br>
The erlang shell is your friend for simple tests like this.<br>
<br>
<br>
bengt<br>
<br>
On 02/12/2015 03:33 PM, Roelof Wobben wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">
Hello,<br>
<br>
I have this code :<br>
<br>
-module(side_effects).<br>
<br>
-export([display_numbers/1]).<br>
<br>
%% display_numbers(N) displays the numbers from
1,2,...+N when N is a non-negative integer.<br>
%% It is not defined for other arguments.<br>
%% When N is a non-negative number, a helper function is
called so it prints out<br>
%% the numbers in the right order. This is a exercise
from the Erlang Programming book<br>
%% where I have to practice side-effects.<br>
display_numbers(Number) when is_integer(Number), Number
> 0 -><br>
display_numbers_loop(0, Number ).<br>
<br>
%% When the control argument)(second argument) is equal
to the number<br>
%% the user has given, the end is reached and the last
number is printed<br>
display_numbers_loop(Number, Number) -><br>
ok;<br>
<br>
%% When the contro argument(second argument) is not equal
to the number<br>
%% and the Current number is even,<br>
%% The control argument is increased by one and the<br>
%% display_numbers_loop function is called again with the
new arguments.<br>
display_numbers_loop(Current, Number) when Current / 2 ==
0 -><br>
io:format("Number:~p~n",[Current + 1]),<br>
display_numbers_loop(Current +1, Number );<br>
<br>
%% When the contro argument(second argument) is not equal
to the number<br>
%% and the Current number is not even,<br>
%% The control argument is increased by one and the<br>
%% display_numbers_loop function is called again with the
new arguments.<br>
display_numbers_loop(Current, Number) when Current / 2 /=
0 -><br>
io:format("Number:~p~n",[Current + 1]),<br>
display_numbers_loop(Current +1, Number ).<br>
<br>
but when I do side_effects(10) I see all the numbers so I
wonder why the when is not working ?<br>
<br>
Roelof<br>
<br>
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