Strings in Haskell are one of the language's sore points. It's something that's mostly a non-issue for those using Haskell day to day, but may be surprising to newcomers.
Haskell's built-in string type is a list of characters. This is mostly for historical reasons, but it's also handy in education (installing extra packages is a barrier for learners; list processing is common in introductory courses, but lists are polymorphic/generic in their element type; lists of characters are a nice concrete type, which follows on easily from "hello world"); also there are arguments about the theoretical elegance of linked lists, KISS for the builtins, whether there's concensus on what the best alternative is, etc.
Anyone who cares about Haskell performance will have hit this early on, and be using a different string implementation, as mentioned in the article. In particular there's ByteString for C-like arrays of bytes, and there's Text which is just a ByteString with extra metadata like character encoding. In fact, ByteString doesn't have to be a single contiguous array: it can be a list of "chunks", where each chunk contains a pointer to an array, an offset and a length; this speeds up many operations, e.g. we can append ByteStrings by adding chunks to the list (pointing to existing arrays), we can take substrings by manipulating the offsets and lengths, etc. This is all perfectly safe and predictable since the data is immutable, where other languages which allow mutation might prefer to make copies of the data to reduce aliasing.
The other aspect is the buffering mode of the handle, which is discussed a little in the article and its comments (e.g. line-based buffering, etc.).
Haskell's built-in string type is a list of characters. This is mostly for historical reasons, but it's also handy in education (installing extra packages is a barrier for learners; list processing is common in introductory courses, but lists are polymorphic/generic in their element type; lists of characters are a nice concrete type, which follows on easily from "hello world"); also there are arguments about the theoretical elegance of linked lists, KISS for the builtins, whether there's concensus on what the best alternative is, etc.
Anyone who cares about Haskell performance will have hit this early on, and be using a different string implementation, as mentioned in the article. In particular there's ByteString for C-like arrays of bytes, and there's Text which is just a ByteString with extra metadata like character encoding. In fact, ByteString doesn't have to be a single contiguous array: it can be a list of "chunks", where each chunk contains a pointer to an array, an offset and a length; this speeds up many operations, e.g. we can append ByteStrings by adding chunks to the list (pointing to existing arrays), we can take substrings by manipulating the offsets and lengths, etc. This is all perfectly safe and predictable since the data is immutable, where other languages which allow mutation might prefer to make copies of the data to reduce aliasing.
The other aspect is the buffering mode of the handle, which is discussed a little in the article and its comments (e.g. line-based buffering, etc.).