In fact, you can have functions of type [Byte] -> [Byte], however, the problem is when you need to get the first set of bytes from a file or stdin. You could so

In fact, you can have functions of type [Byte] -> [Byte], however, the problem is when you need to get the first set of bytes from a file or stdin. You could sort of read this as a function of type FileHandle -> [Byte], which will only very rarely even return the same value twice, let alone guaranteed-always.