Why is Haskell's default string implementation a linked list of chars?

Question

The fact that Haskell\'s default String implementation is not efficient both in terms of speed and memory is well known. As far as I know the [] lists

Answer 1

Why is Haskell's default String implementation a singly-linked list

Because singly-linked lists support:

• induction via pattern matching
• have useful properties, such as Monad, Functor
• are properly parametrically polymorphic
• are naturally lazy

and so String as [Char] (unicode points) means a string type that fits the language goals (as of 1990), and essentially come "for free" with the list library.

In summary, historically the language designers were interested more in well-designed core data types, than the modern problems of text processing, so we have an elegant, easy to understand, easy to teach String type, that isn't quite a unicode text chunk, and isn't a dense, packed, strict data type.