040000 tree 2920a550f1d4e4db600cf3e51fed805239579aa0	01-basic
040000 tree bc722d1dbfb3432247fc65c0f866c21fb86da5c0	02-sharing
040000 tree 22138095c67ee3b0d166d852c7e698a137a2e617	03-subtyping
040000 tree ee22ce38cd820b97f26e474a740fe6ff3ef7e986	04-double-take
040000 tree 5133cdb62fa225997a2589de63dd50d4075e188a	05-splay