Erlide: how to set start module in run configuration? - eclipse

Question

I have problem with setting start module and function in "Run configuration"
I'm doing it that way:
"Run -> Run Configuration" and in "start" section I'm setting
Module: mod,
Function: hello
my code:
-module(mod).
-export([hello/0]).
hello()-> io:format("42").
Now, when I hit "Run" I would like mod:hello() to be execute automatically, but it doesn't work.
What am I doing wrong?

Answer 1

The code does get executed...
When you hit "Run", mod:hello() does get executed. The thing is, the execution of mod:hello() is meant for system initialization, like loading library code and initializing looping states. The side effect of mod:hello(), which is the string "42" as stdout will not be reflected in your Eclipse console. To prove my point, we can create some more explicit and more persistent side effects, like creating a file in the file system called output_file.txt. Change mod.erl to something like this:
-module(mod).
-export([hello/0]).
hello() ->
os:cmd("touch output_file.txt").
Hit "Run", and you will find a output_file.txt file being created under your workspace directory. This is an evidence for the execution of mod:hello().
To achieve what you want...
In an Unix shell:
$ erlc mod.erl
$ erl -noshell -s mod hello -s init stop
42

Answer 2

Depending on what you want to execute, there is an alternative to the answer above: the "live expressions". There is a view with this name in the same place as the console, where you can enter an expression and enable it for evaluation every time a module is recompiled.
This works nicely for expression that aren't heavy to evaluate and that are without side effects, can be used as a form of alternative to having a test suite.