Quoting Paul (2018-12-18 14:28:53)
But wait, I can get the same exception as in C/C++: fromJust Nothing without "if isJust..."! So, Damien is right here - no difference with C and Haskell is not more safe than C here - and you CAN omit checking and to get run time exception.
First, C doesn't give you an exception, it just tramples over memory. The OS jumps through hoops to make it likely that it will start with memory that will cause it to be killed before it does any real damage, but it's still a different beast. But if you really want that behavior could also just do: case x of Just x -> x Nothing -> unsafeCoerce 0 ..and pattern matching doesn't save you. So yes, if you heap on enough pedantry, you can claim that Haskell is not safer than C. But this argument is divorced from the reality of what writing code is actually like in these two languages. Segfaults and memory corruption are the norm in C, and not in Haskell.
C# 8
[...]
modern C++
I did say C, not C# or C++ which are entirely different languages. Type-level nil tracking actually does give you the benefits I describe, though it's not as nice as proper sum types more generally. I did not say that Haskell's Maybe is the only way to achieve this. -Ian