Result

The result of a parse--a Parser[A] returns a Result[A].

There are three cases:

• Success(a,n): a is the value, n is # of consumed characters
• Slice(n): a successful slice; n is the # of consumed characters
• Failure(n,isCommitted): a failing parse

As usual, we define some helper functions on Result. Defining functions on Result gives us better type information--there are cases (see map and map2 below) where Scala will not appropriately refine type information when pattern matching on Result.