Hello folks I've recently asked some questions here about some little type hackery implementing an embedded dsl. But now I wonder if it's worth the effort at all... The thing is enforcing static constraints turns out to be quite time consuming, even for 'reasonble' things. The dsl I'm writing will not primarily be used from Haskell sources, rather more likely be input to the interpreter, and hence dynamic analysis after parsing will occur any way. On the other hand, enforcing them excludes some errors... To give you a flavour, classical example, I could represent expressions simply by 'data Exp' or by 'data Exp a' where a is the type of expression and 4 + "str" is illegal, or by 'data Exp s a' where a is the same and s is an additional property, like some kind of things the expression mentions, and there are restrictions on how Exp s1 and Exp s2 can combine. And s is not otrhogonal with a. There may be more properties. I'd like to hear your thoughts on how practical it is, and to which extent, to use typeful programing for statically enforcing constraints, in real-life applications, where readability and maintainability matter.