added in module for semvar comparisons

This code implements comparisons using (list based) strings as
semantic versions. It follows the stadard dictated by semvar.org.

Signed-off-by: Eric Merritt <ericbmerritt@gmail.com>

ebin/erlware_commons.app

@@ -1,7 +1,11 @@
 %% -*- mode: Erlang; fill-column: 75; comment-column: 50; -*-
 {application, erlware_commons,
  [{description, "Additional standard library for Erlang"},
-  {vsn, "0.0.1"},
+  {vsn, "0.1.0"},
-  {modules, [ec_lists]},
+  {modules, [
+	     ec_lists,
+	     ec_string,
+	     ec_semver
+	    ]},
   {registered, []},
   {applications, [kernel, stdlib]}]}.

src/ec_lists.erl

@@ -48,7 +48,7 @@ fetch(List, Fun)
     end.
 
 %%%===================================================================
-%%% API
+%%% Test Functions
 %%%===================================================================
 
 -ifndef(NOTEST).

src/ec_semver.erl

@@ -0,0 +1,94 @@
+%%%-------------------------------------------------------------------
+%%% @copyright (C) 2011, Erlware LLC
+%%% @doc
+%%%  Helper functions for working with semver versioning strings.
+%%%  See http://semver.org/ for the spec.
+%%% @end
+%%%-------------------------------------------------------------------
+-module(ec_semver).
+
+-exports([
+	  compare/2
+	 ]).
+
+%%%===================================================================
+%%% API
+%%%===================================================================
+
+%% @doc Is semver version string A bigger than version string B?
+%% <pre>
+%% Example: compare("3.2.5alpha", "3.10.6") returns: false
+%% </pre>
+-spec compare(VsnA::string(), VsnB::string()) -> boolean().
+compare(VsnA, VsnB) ->
+    compare_toks(tokens(VsnA),tokens(VsnB)).
+
+%%%===================================================================
+%%% Internal Functions
+%%%===================================================================
+tokens(Vsn) ->
+    [MajorVsn, MinorVsn, RawPatch] = string:tokens(Vsn, "."),
+    {PatchVsn, PatchString} = split_patch(RawPatch),
+    {MajorVsn, MinorVsn, PatchVsn, PatchString}.
+
+split_patch(RawPatch) ->
+    {PatchVsn, PatchStr} = split_patch(RawPatch, {"", ""}),
+    {lists:reverse(PatchVsn), PatchStr}.
+
+split_patch([], Acc) ->
+    Acc;
+split_patch([Dig|T], {PatchVsn, PatchStr}) when Dig >= $0 andalso Dig =< $9 ->
+    split_patch(T, {[Dig|PatchVsn], PatchStr});
+split_patch(PatchStr, {PatchVsn, ""}) ->
+    {PatchVsn, PatchStr}.
+
+compare_toks({MajA, MinA, PVA, PSA}, {MajB, MinB, PVB, PSB}) ->
+    compare_toks2({to_int(MajA), to_int(MinA), to_int(PVA), PSA},
+		 {to_int(MajB), to_int(MinB), to_int(PVB), PSB}).
+
+compare_toks2({MajA, _MinA, _PVA, _PSA}, {MajB, _MinB, _PVB, _PSB}) when MajA > MajB ->
+    true;
+compare_toks2({_Maj, MinA, _PVA, _PSA}, {_Maj, MinB, _PVB, _PSB}) when MinA > MinB ->
+    true;
+compare_toks2({_Maj, _Min, PVA, _PSA}, {_Maj, _Min, PVB, _PSB}) when PVA > PVB ->
+    true;
+compare_toks2({_Maj, _Min, _PV, ""}, {_Maj, _Min, _PV, PSB}) when PSB /= ""->
+    true;
+compare_toks2({_Maj, _Min, _PV, PSA}, {_Maj, _Min, _PV, ""}) when PSA /= ""->
+    false;
+compare_toks2({_Maj, _Min, _PV, PSA}, {_Maj, _Min, _PV, PSB}) when PSA > PSB ->
+    true;
+compare_toks2(_ToksA, _ToksB) ->
+    false.
+    
+to_int(String) ->
+    case catch list_to_integer(String) of
+        Integer when is_integer(Integer) ->
+	    Integer;
+        _ ->
+	    throw(invalid_semver_string)
+    end.
+
+
+%%%===================================================================
+%%% Test Functions
+%%%===================================================================
+
+-ifndef(NOTEST).
+-include_lib("eunit/include/eunit.hrl").
+
+split_patch_test() ->
+    ?assertMatch({"123", "alpha1"}, split_patch("123alpha1")).
+
+compare_test() ->
+    ?assertMatch(true, compare("1.2.3", "1.2.3alpha")),
+    ?assertMatch(true, compare("1.2.3beta", "1.2.3alpha")),
+    ?assertMatch(true, compare("1.2.4", "1.2.3")),
+    ?assertMatch(true, compare("1.3.3", "1.2.3")),
+    ?assertMatch(true, compare("2.2.3", "1.2.3")),
+    ?assertMatch(true, compare("4.2.3", "3.10.3")),
+    ?assertMatch(false, compare("1.2.3", "2.2.3")),
+    ?assertThrow(invalid_semver_string, compare("1.b.2", "1.3.4")),
+    ?assertThrow(invalid_semver_string, compare("1.2.2", "1.3.t")).
+
+-endif.