Pattern matching variables in a case statement in Haskell

Question

If I compare a string literal to a string literal using the case statement, I get the expected behavior: if they are the same - it matches, if they are not - it does not.

Answer 1

Pattern matching in Haskell binds new variables. So when you write:

case x of
    y -> ...

you have now bound a new variable 'y' to the value of 'x'. This is the trivial "pattern". You can see more clearly how the binding works when a constructor is involved:

case x of 
    (a, b) -> ...

Now a and b bind to components of the tuple. And so on for deconstructing and binding other data types. Thus, to match a string literal, you would write:

case x of
    "def" -> ....