Hello, i just thought, that it would be cool to have a special bytecode, which guarantees atomicity for swapping values between two variables. To swap two values, you usually do: | var1 var2 temp | temp := var1. var1 := var2. var2 := temp. But since its non-atomic, a process can be interrupted and such operation is not thread-safe. In order to make it thread safe, you must add even more boilerplate: | var1 var2 temp | semaphore critical: [ temp := var1. var1 := var2. var2 := temp. ] So, i thought , if we could have a special bytecode, then we could write something like: | var1 var2 | var1 :=: var2. So, VM will guarantee that values of var1 and var2 will be swapped atomically, and completely thread-safe. var1 and var2 could be either temps or instance variables, but of course not arguments, since they are not assignable. One thing i don't like, that it will need to introduce a new syntax for atomic-value-swap operator - :=: Or, maybe just reserve a special keyword selector (which is recognized by compiler), so var1 __atomicSwapWith: var2 so it will look like a regular smalltalk syntax, except that its not a message send, but a low-level operation instead. -- Best regards, Igor Stasenko AKA sig.