Initial data commit

Task/Binary-strings/Erlang/binary-strings-1.erl

@@ -0,0 +1,49 @@
+-module(binary_string).
+-compile([export_all]).
+
+%% Erlang has very easy handling of binary strings. Using
+%% binary/bitstring syntax the various task features will be
+%% demonstrated.
+
+
+%% Erlang has GC so destruction is not shown.
+test() ->
+    Binary = <<0,1,1,2,3,5,8,13>>, % binaries can be created directly
+    io:format("Creation: ~p~n",[Binary]),
+    Copy = binary:copy(Binary), % They can also be copied
+    io:format("Copy: ~p~n",[Copy]),
+    Compared = Binary =:= Copy, % They can be compared directly
+    io:format("Equal: ~p = ~p ? ~p~n",[Binary,Copy,Compared]),
+    Empty1 = size(Binary) =:= 0, % The empty binary would have size 0
+    io:format("Empty: ~p ? ~p~n",[Binary,Empty1]),
+    Empty2 = size(<<>>) =:= 0, % The empty binary would have size 0
+    io:format("Empty: ~p ? ~p~n",[<<>>,Empty2]),
+    Substring = binary:part(Binary,3,3),
+    io:format("Substring: ~p [~b..~b] => ~p~n",[Binary,3,5,Substring]),
+    Replace = binary:replace(Binary,[<<1>>],<<42>>,[global]),
+    io:format("Replacement: ~p~n",[Replace]),
+    Append = <<Binary/binary,21>>,
+    io:format("Append: ~p~n",[Append]),
+    Join = <<Binary/binary,<<21,34,55>>/binary>>,
+    io:format("Join: ~p~n",[Join]).
+
+%% Since the task also asks that we show how these can be reproduced
+%% rather than just using BIFs, the following are some example
+%% recursive functions reimplementing some of the above.
+
+%% Empty string
+is_empty(<<>>) ->
+    true;
+is_empty(_) ->
+    false.
+
+%% Replacement:
+replace(Binary,Value,Replacement) ->
+    replace(Binary,Value,Replacement,<<>>).
+
+replace(<<>>,_,_,Acc) ->
+    Acc;
+replace(<<Value,Rest/binary>>,Value,Replacement,Acc) ->
+    replace(Rest,Value,Replacement,<< Acc/binary, Replacement >>);
+replace(<<Keep,Rest/binary>>,Value,Replacement,Acc) ->
+    replace(Rest,Value,Replacement,<< Acc/binary, Keep >>).