What is a lambda expression?

A lambda expression is an anonymous function that can be defined and used directly at the call site without needing to give it a name. Lambda expressions are typically used for concise function definitions, passing functions as arguments, or creating closures.

For example, in the Go language, a lambda expression looks like this:

func(x int) int {
    return x * x
}

It can be invoked immediately or assigned to a variable for later use.