%% The contents of this file are subject to the Mozilla Public License
%% Version 1.1 (the "License"); you may not use this file except in
%% compliance with the License. You may obtain a copy of the License
%% at http://www.mozilla.org/MPL/
%%
%% Software distributed under the License is distributed on an "AS IS"
%% basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
%% the License for the specific language governing rights and
%% limitations under the License.
%%
%% The Original Code is Erlando.
%%
%% The Initial Developer of the Original Code is VMware, Inc.
%% Copyright (c) 2011-2013 VMware, Inc.  All rights reserved.
%%

-module(error_m).

-behaviour(monad).
-export(['>>='/2, return/1, fail/1]).

%% This is really instance (Error e) => Monad (Either e) with 'error'
%% for Left and 'ok' for Right.

-type(monad(A) :: 'ok' | {'ok', A} | {'error', any()}).
-include("monad_specs.hrl").

'>>='({error, _Err} = Error, _Fun) -> Error;
'>>='({ok, Result},           Fun) -> Fun(Result);
'>>='(ok,                     Fun) -> Fun(ok).

return(ok) -> ok;
return(X)  -> {ok,    X}.
fail(X)    -> {error, X}.