<div dir="ltr"><div class="gmail_default" style="font-family:verdana,sans-serif">First "stringer" was a sample for (turned out it was a bad one) simulating protocols. So one could write (it can be more complicated, but whatever):</div>
<div class="gmail_default" style="font-family:verdana,sans-serif"><br></div><div class="gmail_default"><div class="gmail_default"><font face="verdana, sans-serif">test(V) -></font></div><div class="gmail_default"><font face="verdana, sans-serif"> X = ?protocolX(V),</font></div>
<div class="gmail_default"><font face="verdana, sans-serif"> X:act1(),</font></div><div class="gmail_default"><font face="verdana, sans-serif"> X:act2(),</font></div><div class="gmail_default"><font face="verdana, sans-serif"> % ...</font></div>
<div class="gmail_default"><font face="verdana, sans-serif"> X:actN(SomeArguments),</font></div><div class="gmail_default"><font face="verdana, sans-serif"> OtherThings().</font></div><div class="gmail_default"><font face="verdana, sans-serif"><br>
</font></div><div class="gmail_default"><font face="verdana, sans-serif">And act1 .. actN are members of 'protocolX'. This way it's clear that 'V' is behaving as a 'X' (much like interfaces in C#; am I too corrupted?).</font></div>
<div class="gmail_default"><font face="verdana, sans-serif"><br></font></div><div class="gmail_default"><font face="verdana, sans-serif">BTW since I am no Erlang guru, I will follow the rules (for a foreseeable future) as you say here.</font></div>
</div></div><div class="gmail_extra"><br clear="all"><div><div dir="ltr"><div><span style="font-family:tahoma,sans-serif;font-size:large">Kaveh Shahbazian</span><br></div><div><font size="1" face="arial narrow, sans-serif"><div>
“Walking on water and developing software from a specification are easy if both are frozen.” </div><div>― Edward Berard</div><div><a href="http://goo.gl/ZZ2TMu" target="_blank"><img src="http://www.linkedin.com/img/webpromo/btn_myprofile_160x33.png"></a><br>
</div><div><a href="http://stackoverflow.com/users/54467/kaveh-shahbazian" target="_blank"><img src="http://stackoverflow.com/users/flair/54467.png"></a><br></div></font></div></div></div>
<br><br><div class="gmail_quote">On Fri, Dec 13, 2013 at 5:32 PM, Fred Hebert <span dir="ltr"><<a href="mailto:mononcqc@ferd.ca" target="_blank">mononcqc@ferd.ca</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
Hi.<br>
<br>
Despite what Joe says in his book, the history of the feature is that<br>
tuple calls, the form you're using, were kept to allow the deprecation<br>
of parametrized modules.<br>
<br>
In my humble opinion, the 'stateful module' things you're trying to<br>
accomplish for you stringification is non-intuitive and not erlangish (I<br>
would be confused by reading that in a code base). May I suggest the<br>
simpler form, without changing your module:<br>
<br>
stringer:to_string(MyValue)<br>
<br>
instead? You will notice it even saves two characters when being called<br>
over:<br>
<br>
?stringer(MyValue):to_string().<br>
<br>
Without including the macro definition work required, and is more<br>
idiomatic overall. To use it as a function, simply use<br>
<br>
F = fun stringer:to_string/1,<br>
F(MyValue).<br>
<br>
Regards,<br>
Fred.<br>
<div class="im"><br>
On 12/13, Kaveh Shahbazian wrote:<br>
> I do not thing so. Parametrized modules are different than stateful<br>
> modules. Parametrized modules are deprecated and they were always<br>
> provisional.<br>
><br>
> Joe Armstrong in Programming Erlang (2nd Edition, Page 418) talked about<br>
> them and in this same book he was promoting "coming soon" features of R17<br>
> and It's highly unlikely for them to be deprecated.<br>
><br>
> Kaveh Shahbazian<br>
> “Walking on water and developing software from a specification are easy if<br>
> both are frozen.”<br>
> ― Edward Berard<br>
</div>> <<a href="http://goo.gl/ZZ2TMu" target="_blank">http://goo.gl/ZZ2TMu</a>><br>
> <<a href="http://stackoverflow.com/users/54467/kaveh-shahbazian" target="_blank">http://stackoverflow.com/users/54467/kaveh-shahbazian</a>><br>
<div class="HOEnZb"><div class="h5">><br>
><br>
> On Fri, Dec 13, 2013 at 11:40 AM, Dmitry Kolesnikov<br>
> <<a href="mailto:dmkolesnikov@gmail.com">dmkolesnikov@gmail.com</a>>wrote:<br>
><br>
> > Hello,<br>
> ><br>
> > Essentially you are trying to use parametrized modules, which get<br>
> > deprecated in R14/15 and dropped from R16.<br>
> > See for details:<br>
> > * <a href="http://www.erlang.org/news/35" target="_blank">http://www.erlang.org/news/35</a><br>
> > * <a href="http://www.erlang.se/workshop/2003/paper/p29-carlsson.pdf" target="_blank">http://www.erlang.se/workshop/2003/paper/p29-carlsson.pdf</a><br>
> ><br>
> > This type of problems are solvable either via pattern match or currying:<br>
> ><br>
> > -module(stringer).<br>
> > -export([stringer/1,sample/0]).<br>
> ><br>
> > stringer(V) when is_list(V) -><br>
> > fun() -> to_string(V, nop) end;<br>
> > stringer(V) when is_atom(V) -><br>
> > fun() -> to_string(V, nop) end;<br>
> > stringer(_V) -><br>
> > fun() -> not_implemented end.<br>
> ><br>
> > to_string(V, _Nop) -><br>
> > Buffer = io_lib:format("~p",[V]),<br>
> > lists:flatten(Buffer).<br>
> ><br>
> > sample() -><br>
> > io:format("~p~n", [(stringer([1,2]))()]),<br>
> > io:format("~p~n", [(stringer(cute_atom))()]),<br>
> > io:format("~p~n", [(stringer(13))()]).<br>
> ><br>
> ><br>
> > Best Regards,<br>
> > Dmitry<br>
> ><br>
> > On Dec 13, 2013, at 8:31 AM, Kaveh Shahbazian <<a href="mailto:kaveh.shahbazian@gmail.com">kaveh.shahbazian@gmail.com</a>><br>
> > wrote:<br>
> ><br>
> > I wanted to write something like ((IStringer)object).ToString() (in C#)<br>
> > in Erlang. After some studying I've learnt that Elixir has something called<br>
> > Protocols that pretty much resembles the same thing of C# (in an inside-out<br>
> > manner). Then I came up with this idea/code in Erlang - which is nice<br>
> > enough to me like:<br>
> ><br>
> > ?stringer(my_val):to_string().<br>
> ><br>
> > And it either returns the expected value or not_implemented atom!<br>
> ><br>
> > But 2 questions:<br>
> ><br>
> > 1 - Why nobody use this or promote things based on stateful modules in<br>
> > Erlang? (OTP aside and from talking to some Erlangers they did not know<br>
> > that actually OTP is built around this! So really there is a need to change<br>
> > how Erlang is being taught and promoted. It's possible that I am confused.).<br>
> ><br>
> > 2 - Why I get this warning? That call actually never fails.<br>
> ><br>
> > The warning:<br>
> ><br>
> > stringer.erl:18: Warning: invalid module and/or function name; this call will always fail<br>
> > stringer.erl:19: Warning: invalid module and/or function name; this call will always fail<br>
> > stringer.erl:20: Warning: invalid module and/or function name; this call will always fail<br>
> ><br>
> > The code:<br>
> ><br>
> > -module(stringer).<br>
> > -export([to_string/1,sample/0]).<br>
> ><br>
> > -define(stringer(V), {stringer, V}).<br>
> ><br>
> > to_string({stringer, V}) when is_list(V) -><br>
> > to_string(V, nop);<br>
> > to_string({stringer, V}) when is_atom(V) -><br>
> > to_string(V, nop);<br>
> > to_string({stringer, _V}) -><br>
> > not_implemented.<br>
> ><br>
> > to_string(V, _Nop) -><br>
> > Buffer = io_lib:format("~p",[V]),<br>
> > lists:flatten(Buffer).<br>
> ><br>
> > sample() -><br>
> > io:format("~p~n", [?stringer([1,2]):to_string()]),<br>
> > io:format("~p~n", [?stringer(cute_atom):to_string()]),<br>
> > io:format("~p~n", [?stringer(13):to_string()]).<br>
> ><br>
> > And the output is:<br>
> ><br>
> > "[1,2]"<br>
> > "cute_atom"<br>
> > not_implemented<br>
> ><br>
> > _______________________________________________<br>
> > erlang-questions mailing list<br>
> > <a href="mailto:erlang-questions@erlang.org">erlang-questions@erlang.org</a><br>
> > <a href="http://erlang.org/mailman/listinfo/erlang-questions" target="_blank">http://erlang.org/mailman/listinfo/erlang-questions</a><br>
> ><br>
> ><br>
> ><br>
<br>
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</div></div></blockquote></div><br></div>