> I have built plenty of large software systems. And the source of cost in those systems is always -- by at least a factor of a 100 -- was coupling and imprecis

> I have built plenty of large software systems. And the source of cost in those systems is always -- by at least a factor of a 100 -- was coupling and imprecise semantics. This is a wonderfully, astonishingly, gobsmackingly interesting comment for me to read! In my experience of large systems (Haskell-style) types are exactly the thing you need to tame coupling and imprecise semantics. To take one arbitrary but notable example, in a previous job we found several bugs in large industry XML schema^ by converting the schema to Haskell types and noticing, via type errors, that some things didn't match up. ^I forget if the bugs were in the schema itself or in the Java implementation that another team was using. I think a little bit of the former and a lot of the latter.