# Anonymous function

In computer science and mathematics, an anonymous function is a function with no name. Usually, a function is written like: ${\displaystyle f(x)=x^{2}-x+42}$. It can be written anonymously as ${\displaystyle x\rightarrow x^{2}-x+42}$. Anonymous functions exist in most functional programming languages and most other programming languages where functions are values.

## Examples in some programming languages

Each of these examples show a nameless function that multiplies two numbers.

### Python

Uncurried (not curried):

(lambda x, y: x * y)


Curried:

(lambda x: (lambda y: x * y))
</source>

When given two [[Number|numbers]]:

<syntaxhighlight lang="python">
>>>(lambda x: (lambda y: x * y)) (3) (4)
12
</source>
\x -> \y -> x * y
\x y -> x * y


When given two numbers:

>>> (\x -> \y -> x * y) 3 4
12
</source>

The function can also be written in [[point-free|point-free (tacit)]] style:
(*)
</source>

===Standard ML===
Uncurried:
<syntaxhighlight lang="sml">
fn (x, y) => x * y
</source>

Curried:
<syntaxhighlight lang="sml">
fn x => fn y => x * y
</source>Point-free:<syntaxhighlight lang="sml">
(op *)


### JavaScript

Uncurried:

(x, y) => x * y

function (x, y) {
return x * y;
}


Curried:

x => y => x * y

function (x) {
return function (y) {
return x * y;
};
}
</source>

===Scheme===
Uncurried:<syntaxhighlight lang="scheme">
(lambda (x y) (* x y))


Curried:

(lambda (x) (lambda (y) (* x y)))
</source>Point-free:<syntaxhighlight>
*


### C++ 11

Uncurried: <syntaxhighlight lang="cpp"> [](int x, int y)->int { return x * y; }; </source> Curried: <syntaxhighlight lang="cpp"> [](int x) { return [=](int y)->int { return x * y; }; }; </source>

### C++ Boost

Uncurried:<syntaxhighlight lang="cpp"> _1 * _2 </source> Note: What you need to write boost lambda is to include <boost/lambda/lambda.hpp> header file, and using namespace boost::lambda, i.e. <syntaxhighlight lang="cpp">

1. include <boost/lambda/lambda.hpp>

using namespace boost::lambda; </source>