On 7/22/14, 3:03 AM, Don wrote:
I don't really believe that there are two 'railway tracks' in the sense that that presentation implies. Once an error has occurred, typically not much more pipeline processing happens. As for Unix, stdout from one step is tied to stdin, but stderr is output only. There may be further processing of the stderr stream (eg, errors may be reported to a database), but the steps are completely independent from the main stdin-stdout track. I think you get a messy design if you try to combine both into a single pipeline.
The nice thing is that once the red track is taken, things go through the other functions (which weren't written to take care of errorneous inputs) automatically at a small syntactic cost (the "<>>" operator). -- Andrei