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module(location).
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%% TYPES %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
type type() :: {non_neg_integer(), non_neg_integer()}.
export_type([type/0]).
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%% EXPORTS %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
export
(
[
decode/1,
encode/1
]
).
export
(
[
apply_direction/2,
dist/2
]
).
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%% LOCAL FUNCTIONS %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
spec validate ({integer(), integer()}) > type().
validate ({X, Y}) >
true = (X >= 0),
true = (Y >= 0),
{X, Y}.
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%% EXPORTED FUNCTIONS %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
spec apply_direction (direction:enum(), type()) > type().
apply_direction (left, {X, Y}) >
validate({(X  1), Y});
apply_direction (right, {X, Y}) >
validate({(X + 1), Y});
apply_direction (up, {X, Y}) >
validate({X, (Y  1)});
apply_direction (down, {X, Y}) >
validate({X, (Y + 1)}).
spec dist(type(), type()) > non_neg_integer().
dist ({OX, OY}, {DX, DY}) >
(abs(DY  OY) + abs(DX  OX)).
spec encode (type()) > list(non_neg_integer()).
encode ({X, Y}) > [X, Y].
spec decode (list(non_neg_integer())) > type().
decode ([X, Y]) when (is_integer(X) and is_integer(Y)) > validate({X, Y}).
