Deniz Dogan
One explanation is that isBlah asks "is this thing a blah", but we're not asking that because there is an indirection via the filepath. We're asking "does this filepath refer to a directory" not "is this filename a directory".
I think see what you mean, but I find the argument more of an excuse to the poor naming than a solid argument for it. Following the convention and intuition that most users have should be more important than making the (sometimes unnecessary) distinction between a directory and the path to it.
It is more important to be consistent and logical than to follow conventions and intuitions. And at any rate, convention is that 'isFoo' is a pure function with the type 'FooType -> Bool', clearly different from 'doesDirectoryExist', which returns an IO action. So IMO 'isDirectory "/foo/bar/"' should always return false, since it is a string, not a directory. -k -- If I haven't seen further, it is by standing in the footprints of giants