sasajuric:
I agree with app vs library point, but I’m not sold on the conclusion. I don’t have enough of a sample to know what “the wast majority of applications” does, but in my limited experience of trying both approaches for a couple of years, I definitely prefer app code with specs, because they help me understand what are the allowed inputs and what are the possible outputs, which in turn reduces the uncertainty when reasoning about the code.
To clarify, my conclusion was that in my “real-world” experience people don’t tend to write specs for applications, not that they shouldn’t write specs. Personally I’m in favor of it for precisely the reasons you mentioned.
sasajuric:
This is why I prefer to say that types are first and foremost about documenting, not about catching bugs. When a type checker complains, it means that there is a discrepancy between the spec and the implementation. From the standpoint of the desired program behaviour we don’t know what is wrong (in fact the program might even be correct), but we do know that the documentation (spec) doesn’t match the code, so we need to fix something to sync them.
My feelings exactly.
