What are some examples of type constraints in Haskell?

What are some examples of type constraints in Haskell?

Type constraints in Haskell specify that a type must satisfy certain properties. For example, the Num type class requires that a type supports numeric operations.

Can you give me a specific code example?

Sure! Here's a simple example:

add :: Num a => a -> a -> a
add x y = x + y

In this function, Num a => is the type constraint that ensures a can be used with numeric operations.

What happens if I try to use a non-numeric type?

If you try to use a non-numeric type with the add function, Haskell will give you a compile-time error, indicating that the type does not satisfy the Num constraint.

Are there other type classes with constraints?

Yes, there are many type classes in Haskell, such as Eq for equality checks and Ord for ordering, each with their own constraints.