Perhaps you've not used Haskell? There are no "built in" operators in Haskell, other than " ", which is function application, and which cannot be overridden. A

Perhaps you've not used Haskell? There are no "built in" operators in Haskell, other than " ", which is function application, and which cannot be overridden. Additionally, any "infix operator" can be used in prefix form, by surrounding it in parens - and any function name can be used in infix form, by surrounding it in `backticks`. All other operators, like +, -, $, <, <$>, >>=, are defined in libraries (specifically in Prelude, the "standard library") - these operators cannot be overloaded in ad-hoc manner as operator overloading is done in other languages (bar qualified module imports) - to make use of one of these operators you must implement an instance of the class which contains it, such as Num for +, -. There's also the requirement to implement fromInteger, signum, negate, etc in Num. (If you can't think of a valid "fromInteger" implementation for your custom type, it's obviously not a Num). Also, some classes have associated laws which should prevent you from using them incorrectly Admittedly the class/instance scenario could be improved with further checking of these "laws", but that would basically require a full theorem prover baked into the language - something that Haskell will probably get sooner or later. There's still what I would consider "operator abuse" in Haskell - it's not that of overloading existing operators, but that of introducing new operator aliases for virtually every function in your library, as http://hackage.haskell.org/package/lens-4.1.2/docs/Control-Lens-Operators.html http://hackage.haskell.org/package/lens-4.1.2/docs/Control-L... does (yuck). A nice convenient feature of Haskell is that you can scrap the official Prelude library (-XNoImplicitPrelude) and roll your own, as some others have done (e.g, http://hackage.haskell.org/package/classy-prelude http://hackage.haskell.org/package/classy-prelude). This allows you to effectively "clean up" some of the warts from the early design of the language, so it can continually improve - rather than needing to invent a whole new language when we decide it's not what we want. Num is an example of a class which gets lots of stick, because we'd often like to implement either of addition or mulitplication, but not both.