ezyang’s blog

the arc of software bends towards understanding

Flipping arrows in coBurger King

Category theory crash course for the working Haskell programmer. A frequent question that comes up when discussing the dual data structures—most frequently comonad—is “What does the co- mean?” The snippy category theory answer is: “Because you flip the arrows around.” This is confusing, because if you look at one variant of the monad and comonad […]

  • July 14, 2010