Simple Linear-Time Algorithms to Test Chordality of Graphs, Test Acyclicity of Hypergraphs, and Selectively Reduce Acyclic Hypergraphs

An article of golfing equipment has a golf tee attached to a spring-biassed reel by a length of string. The reel is mounted in a casing which receives the tee when the spring rotates the reel to wind the spring onto it. The reel is normally locked by a one-way ratchet but is released to wind in the string by a push-button which has a spike and is detachable from the casing so as to be usable as a ball marker. When practising, the cord can be aligned with the green or hole and used as an aid in swinging the club face in the correct direction. The casing has a spring-clip so that the article can be clipped into the golfer's pocker when he is not using it.