Nested function

In many languages, functions can be nested, so there are outer functions and inner functions. The inner function can then access the variables of the outer function. In most languages, the inner function can also modify variables from the outer function.

The following examples for MakeList or makeList generate the following text:

1. first
2. second
3. third

C#

<lang csharp> string MakeList(string separator) {

   var counter = 1;

   var makeItem = new Func<string, string>((item) => {
       return counter++ + separator + item + "\n";
   });

   return makeItem("first") + makeItem("second") + makeItem("third");

}

Console.WriteLine(MakeList(". ")); </lang>

JavaScript

<lang javascript> function makeList(separator) {

 var counter = 1;

 function makeItem(item) {
   return counter++ + separator + item + "\n";
 }

 return makeItem("first") + makeItem("second") + makeItem("third");

}

console.log(makeList(". ")); </lang>

Lua

<lang lua> function makeList(separator)

 local counter = 1

 local function makeItem(item)
   return counter .. separator .. item .. "\n"
 end

 return makeItem("first") .. makeItem("second") .. makeItem("third")

end

print(makeList(". ")) </lang>

References

• Wikipedia article on nested functions