Higher-order function on OOFP 2025-26

Anonymous function

Mon, 01 Jan 0001 00:00:00 +0000

Anonymous function #

We have seen in the dedicated section that a function can be written anonymously, as a lambda expression.

Anonymous functions are a traditional feature of functional languages (like Haskell). But they have also been integrated to a variety of imperative languages, for instance:

Python (since 1994),
Javascript (since its initial release in 1995),
C# (since 2007)
C++ (since 2011)
Java (since 2014)
Rust (since its initial release in 2015)

In Haskell #

Syntax. “$\lambda x.$” in Haskell is written \x ->

Currying

Mon, 01 Jan 0001 00:00:00 +0000

Currying #

Functional programs traditionally define functions in curried form (for a definition, we refer to the dedicated section).

In Haskell #

Syntax #

A Haskell function can (in theory) take a tuple as argument.

Example.

power :: (Int, Int) -> Int
power (x,y) = x^y

However, functions in curried form are usually preferred, because they are more versatile.

Example. The function above in curried form can be written:
power :: Int -> (Int -> Int)
power = \x -> (\y -> x^y)
or equivalently:

A few higher-order functions

Mon, 01 Jan 0001 00:00:00 +0000

A few higher-order functions #

We introduce a few convenient higher-order functions.

In Haskell #

`filter` #

The function filter retains elements of a list that satisfy a certain condition.

Higher-order function on OOFP 2025-26

Anonymous function

Anonymous function #

In Haskell #

Currying

Currying #

In Haskell #

Syntax #

A few higher-order functions

A few higher-order functions #

In Haskell #

filter #

`filter` #