Modules and function "encapsulation"

Silas Silva silasdb@REDACTED
Wed Sep 1 05:16:49 CEST 2010

Hello all.

I'm a newbie in Erlang and functional programming.  Just got amazed to
see how fast I could make a MVC application in Erlang, using its great
pattern matching capabilities (not present in mainstream imperative
languages) and other features.

A doubt regarding modules, though, is in my mind:

In my MVC application, the Model (for now, an interface to a Mnesia
database) has the start/0 (exported) function.  The Controller (which
imports Model's start/0) also defines its own start/0 function.  When
trying to compile the Controller, I got the following error:

    defining imported function start/0

I decided to make some research on my favourite search engine and found
this thread on an Erlang forum:

There, people talks about overloading.  I can have start/0 in one module
and start/1, start/2 etc. in another module, which "extends" the start
function, but I can't have two start/0 functions.  That is okay, but I
thought that start/0 for a module would be totally different from
start/0 from another module and both would not conflict.  So, why there
is the module prefixing syntax (controller:start()), -import and

How do you deal with that?  You just make functions name unique among
all modules?  This approach looks like in a big C program (e. g.: OS
monolithic kernel), where symbols cannot conflict because, even though
they are compiled in different .o files, the linker complains when
putting everything together.

Any recommendation?


Silas Silva

More information about the erlang-questions mailing list