> I don't think it breaks the concept of pipes. I think it breaks the concept of _pipelines_. Fair enough. > I don't see why a pipeline should be unidirectio

> I don't think it breaks the concept of pipes. I think it breaks the concept of _pipelines_. Fair enough. > I don't see why a pipeline should be unidirectional though. Piplines usually only carry material from one side to the other :) (yes, pneumatic ones are different :)) It's part "just because that made sense at the time" and partially because it does make sense: Give data to A, take the output and process it, give that to C, &c. However, a bidirectional, or even multiple, pipe would have some advantages, such as signaling.