erlang

Tips and Tricks for Erlang

Common Test

Run CT tests in Verbose mode

If you want to see CT output in the console:

make ct CT_OPTS="-verbosity=10"

List of Available CT_OPTS

https://docs.oracle.com/cd/E36784_01/html/E36870/ct-run-1.html

Erlang.mk

Running Erlang.mk in verbose debug output mode

Sometimes it is necessary to debug how Erlang MK does what it does.

make ct V=2

Lists

lists:flatten

lists:flatten does not flatten a single level of a list, it flattens a "deep" list, meaning that it flattens as long as it finds a list.

For example:

lists:flatten([a, [b, [c]]]).
[a,b,c]

Instead, something like this can be used:

flat_one(List) -> lists:flatmap( fun(L) -> L end, List).

flat_one([a, [b, [c]]]).
[a, b, [c]]

This is important because many times in Erlang you use proplists which are lists, and if you flatten a list of proplists, then you will run into issues. This is also the reason why on an iolist you can call lists:flatten to flatten it.