Haskell中的单引号和双引号

Question

Consider:

ghci> :t 'a'
'a' :: Char
ghci> :t "a"
"a" :: [Char]

Why is it treating single and double quotes differently, and is that important?

Answer 1

This is just like C/C++/C#/Java and other programming languages. Single quotes means single character, double quotes means character array (string).

In Haskell, 'c' is a single character ( Char ), and "c" is a list of characters ( [Char] ).

You can compare this to integers and lists of integers:

ghci> let a = 1
ghci> let b = [1,2,3]
ghci> :t a
a :: Integer
ghci> :t b
b :: [Integer]

It is important because there has to be a distinction between single elements and a list of elements. You can perform different operations on simple elements, and different operations on lists.

Answer 2

They're interpreted differently because they just are (that's just how the language is defined). This is important because a Char and a [Char] aren't the same thing. Other than that I'm not sure what you're trying to ask here.