> In Java, for example, I can CTRL+Click on a data type and the IDE will show me the definition Java doesn't track the types as well as HM does. Specifically,

> In Java, for example, I can CTRL+Click on a data type and the IDE will show me the definition Java doesn't track the types as well as HM does. Specifically, if I treat a Stream as a Mappable, I lose the static type info, and can only get it back via casting. In an HM language, e.g. Haskell, my object is statically a Stream type everywhere it's used, even if I'm doing Mappable stuff to it.