rebar_erl_vsn

defines for erlang versions

Build

$ rebar3 compile

Use

Add the plugin to your rebar config:

{plugins, [rebar_erl_vsn]}.
{provider_hooks, [{pre, [{compile, erl_vsn}]}]}.

Then just call your plugin directly in an existing application:

$ rebar3 compile
===> Fetching rebar_erl_vsn
===> Compiling rebar_erl_vsn
<Plugin Output>

Defines

Each major/minor pair get a define like 17.5 or 18.0 in addition the following 'events' are defined too (in combination with the corresponding version):

new_hash (16.0) - new crypto:hash functions are the default and old ones deprecated.
maps, namespaced_types (17.0) - maps are introduced, types like dict() now require a namespace.
large_maps (18) - large maps are now feasable, while in R17 they caused performance problems

Examples

Code that runs on R18 and above:

-ifdef(&#39;18.0&#39;).
version() ->
  "18 and above".
-else.
version() ->
  "before 17".
-endif.

Targeting R17 (all variants) specially

-ifdef(&#39;17.0&#39;).
-ifndef(&#39;18.0&#39;).
%% Code only executed in R17.*
-else.
%% Code executed for R18+
-endif.
-else.
%% Code executed < R17
-endif.

md5 function that does not throw deprecation warnings:

-ifdef(new_hash).
md5(Data) ->
  crypto:hash(md5, Data).
-elseif.
md5(Data) ->
  crypto:md5(Data).
-endif.