◊(Local Yarn Code "Diff")

  ◊dialogue{
    ◊say["Tavi"]{You also write fiction, or you used to. Do you still?}
    ◊say["Lorde"]{The thing is, when I write now, it comes out as songs.}
  }
}|

@defproc[(index [heading string?] [elements xexpr?] ...) txexpr?]
@defproc[(index [#:key key string? ""] [elements xexpr?] ...) txexpr?]

Creates an entry in the keyword index under @racket[_heading] that points back to this spot in the
document. If @racket[_elements] is not empty, the web edition of the document will use it as the
contents of an understated hyperlink to back to @racket[_heading] in the keyword index.
Creates a bidirectional link between this spot in the document and an entry in the keyword index
under @racket[_key]. If @racket[_key] is not supplied, the string contents of @racket[_elements] are
used as the key.

The example below will create two index entries, one under the heading “compassion” and one under
the heading “cats”:

@codeblock|{
  #lang pollen

  “I have a theory which I suspect is rather immoral,” Smiley 
  went on, more lightly. “Each of us has only a quantum of 
  ◊index["compassion"]{compassion}. That if we lavish our concern
  on every stray ◊index["cats"] cat we never get to the centre of 
  ◊index{compassion}. That if we lavish our concern on every
  stray ◊index[#:key "cats"]{cat} we never get to the centre of 
  things. What do you think of it?” 
}|

@defproc[(note [#:date date-str non-empty-string?]
               [#:author author string? ""]
               [#:author-url author-url string? ""]
               [#:disposition disp-str string? ""]) txexpr?]