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.