[foldr]

> Because side effects are controlled, you are forced by the type checker to handle runtime errors (or crash).

This is generally true in idiomatic Haskell code, but in fact even pure functions in Haskell can throw runtime exceptions, and you are not forced to handle these.

[sterlind]

correct me if I'm wrong, but can't you add a compiler flag to prohibit using functions that can panic like "error" and "head"?

aside from that, you'd just need to worry about OOMs and faults in native code.

[massysett]

I guess that would be nice, but no, I’ve never heard of anything like that.

“error” is simply bottom. Bottom is an inhabitant of every Haskell type. There’s no straightforward way to just turn it off.

[renox]

Looks like the null-pointer mistake no?

[foldr]

Bottom has to be a member of every type because functions aren't guaranteed to terminate, so there's no really any way around that within the confines of a general purpose programming language.

That admittedly doesn't entail that Haskell ought to have special functions like 'error' that invite the programmer to explicitly introduce bottom values as a mechanism of signaling errors. However, in the real world, executing any function may raise an exceptional condition at any time (e.g. an out of memory error), regardless of programming language.

[renox]

> Bottom has to be a member of every type because functions aren't guaranteed to terminate,

I don't understand: if the function you called doesn't terminate then you're blocked so I don't see why this should impact the types..

[foldr]

More info here: https://wiki.haskell.org/Bottom As bottom is the value of a non-terminating computation and a computation of any type may fail to terminate, bottom must inhabit all types. The same goes for 'error'. Although in real world Haskell code (using GHC) you can trap error values if you really want to, so 'error' isn't in fact indistinguishable from non-termination.