Write down definitions that have the following types; it...

Write down definitions that have the following types; it does not matter what the definitions actually do as long as they are type correct.
bools :: [Bool]

nums :: [[Int]]

add :: Int -> Int -> Int -> Int

copy :: a -> (a,a)

apply :: (a -> b) -> a -> b

Key Concepts

Higher-Order Functions

Higher-order functions are functions that either take other functions as arguments or return functions as results. This concept is demonstrated by signatures that include function types as parameters, allowing for powerful abstraction and composition in functional programming.

Polymorphism

Polymorphism, particularly parametric polymorphism, allows functions to operate on any data type without depending on the specific type. The use of type variables like 'a' and 'b' in type signatures enables the creation of generic and reusable code components.

Function Currying

Function currying is a technique where a function with multiple parameters is decomposed into a sequence of functions, each taking a single argument. This is intrinsic to Haskell's approach to functions, allowing functions like 'add :: Int -> Int -> Int -> Int' to be partially applied.

Type Signatures

Type signatures are explicit declarations of the type of a variable or function. In a strongly typed language like Haskell, they ensure that expressions are used consistently and correctly, and serve as a form of documentation that clearly expresses what kinds of values a function takes and returns.

Lists

Lists are fundamental data structures that hold collections of elements, all of the same type. They can be nested, such as a list of lists, and are defined using square brackets. This concept is essential for constructing complex data while maintaining type safety.

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