http://hackage.haskell.org/trac/ghc/ticket/1695 This function is like unzip for a list of Eithers instead of tuples. According to google code search, I am at least the 5th person to implement this function: http://www.google.com/codesearch?hl=en&lr=&q=%22%5BEither+a+b%5D+-%3E+%28%5Ba%5D%2C%5Bb%5D%29%22&btnG=Search I opted for the name unzipEithers because the function is similar to two existing functions: unzip and catMaybes. It seems less similar to partition, because partition does not desconstruct the values, it just divides them into to two groups. I have no particular attachment to the name however. I modeled the implementation after unzip and partition. Hopefully I made effective use of the irrefutable patterns and laziness, but someone else should verify. j.