[erlang-questions] Parameterized module initialization

Joe Armstrong <>
Tue Jun 26 14:53:18 CEST 2012


There is an undocumented way of doing this (which one day will become standard)

Suppose we define X as follows:

> X = {mod1, a,b,c}.
{mod1, a,b,c}.

X is now an instance of a parameterised module. if we now call the
function X:func1(x,y) then what actually gets called is the function
mod1:func1(x,y,{mod1,a,b,c})

So for example if we define a module sneaky.erl like this:

   -module(sneaky).
   -export([test/2, hide/1]).

   test(X, Y) ->  {sneaky, X, Y}.

   hide(Something) ->
      {sneaky, Something}.

Then in the shell we can do this:

1> c(sneaky).
{ok,sneaky}
2> X = sneaky:hide({rectange,10,file,"foo"}).
{sneaky,{rectange,10,file,"foo"}}
3> X:test(abc).
{sneaky,abc,{sneaky,{rectange,10,file,"foo"}}}

Cheers

/Joe



On Tue, Jun 26, 2012 at 1:09 PM, Zhemzhitsky Sergey
<> wrote:
> Hi there,
>
>
>
> I’d like to use parameterized module to save some readonly staff and use it
> later at every function call.
>
>
>
> As I understand the compiler implicitly makes every function have parameters
> of the module, so even the function with zero arguments will be exported as
> a function with arity that corresponds to the number of module parameters.
>
>
>
> Is it possible to have a function in a parameterized module that can be
> exported without any parameters of the module?
>
>
>
> Best Regards,
>
> Sergey
>
>
>
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