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node Sofar( X : bool ) returns ( Sofar : bool );
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let
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Sofar = X -> X and pre Sofar;
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tel
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node excludes2( X1, X2 : bool ) returns ( excludes : bool );
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let
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excludes = not ( X1 and X2 );
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tel
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node voiture(m,s: bool) returns
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( toofast, stop, bump: bool;
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dist, speed, time: int;
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move: bool; second, meter: bool );
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let
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meter = false -> (m and not s);
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second = false -> s;
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move = true -> pre(move and not stop and not toofast and not bump);
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dist = 0 -> if move and meter then pre(dist)+1
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else pre(dist);
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speed = 0 -> if not move and second then 0
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else if move and meter then pre(speed) - 1
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else pre(speed);
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time = 0 -> if second then pre(time) + 1
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else pre(time);
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toofast = speed >= 3;
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stop = time >= 4;
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bump = dist = 10;
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tel
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node top(m, s : bool) returns (OK : bool);
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--@ contract guarantees OK;
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var toofast, stop, bump: bool;
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dist, speed, time: int;
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move: bool; second, meter: bool;
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env : bool;
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let
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(toofast, stop, bump, dist, speed, time, move, second, meter) = voiture(m,s);
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env = Sofar( excludes2( m, s ) and dist < 32767);
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OK = env => dist >= 0 and dist < 11 and speed < 4 and speed >= 0;
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--%MAIN;
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--%PROPERTY OK=true;
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tel
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