infix function

An infix function is a function that can be invoked via infix notation. It is a special type of function and has specific rules to satisfy. One of the most common infix function is the to function to create a Pair object. It can be invoked in this way
```
1 to "apple"
```
instead of
```
1.to("apple")
```
and still produce the same Pair\<Int, String> object.