datum

%%
%%   Copyright 2016 Dmitry Kolesnikov, All Rights Reserved
%%
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%%   you may not use this file except in compliance with the License.
%%   You may obtain a copy of the License at
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%%       http://www.apache.org/licenses/LICENSE-2.0
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%%   distributed under the License is distributed on an "AS IS" BASIS,
%%   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
%%   See the License for the specific language governing permissions and
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%%
%% @doc
%%   identity monad
-module(m_identity).

-export([unit/1, fail/1, '>>='/2, putT/1, getT/1]).

-type m(A)    :: A.
-type f(A, B) :: fun((A) -> m(B)).

%%
%%
-spec unit(A) -> m(A).

unit(X) ->
   X. 

%%
%%
-spec fail(_) -> _.

fail(X) ->
   throw(X).

%%
%%
-spec '>>='(m(A), f(A, B)) -> m(B).

'>>='(X, Fun) ->
   Fun(X).

%%
%%
-spec putT(_) -> m(_).

putT(X) -> 
   X.

%%
%%
-spec getT(_) -> m(_).

getT(X) -> 
   X.