[erlang-questions] Passing functions as arguments requires export?

[Kenny Stone]

'incr' will be called from the lists module, not the test module, so it
cannot access it without being exported.

This is one way to do what you want:

res() -> lists:map(fun incr/1, [0,1,2]).

Kenny

On Wed, Nov 3, 2010 at 12:24 PM, Michal D. <michal.dobrogost@REDACTED>wrote:

> Hi All,
>
> I'm having some problems working with functions in Erlang.  Specifically,
> passing functions as arguments. Given the following module:
>
> -module(test).
> -export([res/0]).
>
> res() -> lists:map({test,incr}, [0,1,2]).
>
> incr(X) -> X + 1.
>
> I stumbled upon the syntax {test,incr} to pass a (not anonymous) function.
> When I go to run this code in the emulator, I get an error that doesn't get
> resolved unless I add "incr/1" to the export list.  However, there's no
> reason to export the function because I don't ever want to call it
> directly.  What am I missing?
>
> > c(test).
> > test:res().
> ** exception error: undefined function test:incr/1
>     in function  lists:map/2
> >
>
> Cheers,
>
> Michal
>