Hi, when I'm teaching OO one of the most interesting subjects is the implementation of control flow structures with closures. Having to implement #ifTrue: only with objects and messages produces in some students the "click" we are looking for, the "ah!" that makes them see the real difference with procedural languages and most no pure object languages (java, c#, etc). When teaching the execution model, I use the #whileTrue: implementation to show them that it is also possible to implement such a thing with just objects and messages. The last semester to my surprise I saw that the #whileTrue: implementation in Pharo is cumbersome, at least for teaching porpoises, because it is based on the "hidden" detail that #whileTrue: is inlined, therefore never sent and its method never executed. The VisualWorks implementation is clearer because it is a recursive implementation that seems to work without knowing that #whileTrue: is inlined (and has a nice comment that explains that implementation detail). Anyway, just for teaching porpoises I thought that providing another implementation would be nice, an implementation based on the execution context, an implementation completely based on objects and messages. For example: whileTrue: aBlock self value ifTrue: [ aBlock value. thisContext restart ] I think it is an interesting example that allows the students to see how we can manipulate the execution environment from inside Smalltalk itself... Anyway, just a comment... not sure if it makes sense to change the implementation just because of this, but maybe putting a comment explaining this option would be nice. Bye, Hernan.