Scala Parser Issues

Question

I am having issues testing out the Scala Parser Combinator functionality for a simple Book DSL.

Firstly there is a book class:

case class Book (name:Stri         


        

Answer 1

When you use ~> or <~, you are discarding the element from which the arrow comes. For example:

"book" ~> stringLit // discards "book"
"book" ~> stringLit ~> "has" // discards "book" and then stringLit
"book" ~> stringLit ~> "has" ~> "isbn" // discards everything except "isbn"
"book" ~> stringLit ~> "has" ~> "isbn" ~> stringLit // discards everything but the last stringLit

You could write it like this:

def bookSpec: Parser[Book] = ("book" ~> stringLit <~ "has" <~ "isbn") ~ stringLit ^^ {
  case name ~ isbn => new Book(name,isbn) 
}