> Modules seem much more important than either of those. Modules solve an immediate and obvious pain: unacceptably long compile times. Sum types are more prof

> Modules seem much more important than either of those. Modules solve an immediate and obvious pain: unacceptably long compile times. Sum types are more profound. Anyone having tasted an ML derivative (as I have) would dearly miss them. Seriously, once you've tasted sum types, you'll want to use them everywhere: option types, error returns, abstract syntax trees (JSON, XML, compilers…), you name it, sum types probably solve it. Sum types are no panacea, but if you squint your eyes just right they're pretty damn close.