Aaron Tomb
Huh? Type safety buys [...] nothing about dereferencing null pointers, which are the moral equivalent of Nothing.
What type safety buys you, in my mind, is that Nothing is only a valid value for explicit Maybe types. In cases where you don't use Maybe, the "null" situation just can't occur. In languages with null pointers, any pointer could possibly be null.
To write Haskell that is obviously safe, you need to check all cases of algebraic data types - both Just and Nothing. To do something similar in C, you need to check every pointer for NULL. The great thing about Maybe is that once I've checked it isn't Nothing, I can extract the value and dispense with further checks. foo mbx = maybe default (bar x) mbx Usually, you don't want to go on processing a NULL pointer anyway, but in C, 'bar' might be called with NULL, so it'll have to check it again. And 'bar' is less likely than 'foo' to be able to do anything sensible with NULL, and thus 'foo' needs to be able to handle errors returned from 'bar', too. I think an important reason we get NULL pointer SEGVs is that all this checking when you "know" it can't happen gets tedious, and thus ignored and forgotten. -k -- If I haven't seen further, it is by standing in the footprints of giants