> 2. When you want to implement a method which applies to multiple libraries, you end up writing `fooString`, `fooInteger`, `fooDatetime` etc (or foo(String), f

> 2. When you want to implement a method which applies to multiple libraries, you end up writing `fooString`, `fooInteger`, `fooDatetime` etc (or foo(String), foo(Integer)) etc. DRYing is too hard. So you end up writing 10x more methods This is only a problem in typed languages without generics (like go) or without sum types (like go). With generics, the compiler takes care of writing fooInteger, fooDatetime, etc. With sum types, the compiler verifies that you’ve handled all of the cases in your foo function.