when I integrated http://code.google.com/p/pharo/issues/detail?id=936 save then load the trait package testPrinting | composition1 composition2 | composition1 := ((self t1 - { #a } + self t2) @ { (#z -> #c) } - { #b. #c } + self t3 - { #d. #e } + self t4) @ { (#x -> #a). (#y -> #b) }. composition2 := self t4 @ { (#x -> #a). (#y -> #b) } + self t1 - { #a } + self t3 - { #d. #e } + self t2 - { #b. #c }. self assertPrints: composition1 printString like: 'T1 - {#a} + T2 @ {#z->#c} - {#b. #c} + T3 - {#d. #e} + T4 @ {#x->#a. #y->#b}'. self assertPrints: composition2 printString like: 'T4 @ {#x->#a. #y->#b} + T1 - {#a} + T3 - {#d. #e} + T2 - {#b. #c}' get cut as testPrinting | composition1 composition2 | composition1 := ((self t1 - { #a } right parenthesis expected -> Not fun.