> You can ignore invalid data for as long as you want, but you can also draw lines and say "it can't have been ignored if flow gets to here". (from comment I l

> You can ignore invalid data for as long as you want, but you can also draw lines and say "it can't have been ignored if flow gets to here". (from comment I linked above) I was talking about this property of Maybe. I was thinking that assigning a NaN value to a boolean should probably be "fine" (no exception), but using that when branching would mean that this carried-forward-error (which the NaN represents, effectively) is just about to go beyond "infecting" just data, to affecting code flow. So, throw.