Blank or empty X-expression? #38

I'm following the decoding example from the third Pollen tutorial to define handlers on the root tag. In particular, I'm trying to automatically insert paragraph tags, but not insert <br/> tags for single-line breaks. In order to do that, I'm using the following code, trying to reuse the functions in decode.rkt:

◊(define (mk-para elements)
   (detect-paragraphs elements
                      #:tag 'p
                      #:linebreak-proc (lambda (x) (detect-linebreaks x #:insert '()))))

◊(define (root . elements)
   (make-txexpr 'root null
                (decode-elements elements
                                 #:txexpr-elements-proc mk-para
                                 #:string-proc (compose smart-quotes smart-dashes))))

The main difference from the code in decode.rkt is that I'm trying to use '() as the tag to insert in place of a line-break instead of '(br). However, this causes a contract violation because '() is not a valid X-expression. Perhaps there should be some notion of a blank or empty X-expression that does not translated to anything?

I'm following the decoding example from the third Pollen tutorial to define handlers on the `root` tag. In particular, I'm trying to automatically insert paragraph tags, but _not_ insert `<br/>` tags for single-line breaks. In order to do that, I'm using the following code, trying to reuse the functions in `decode.rkt`: ``` ◊(define (mk-para elements) (detect-paragraphs elements #:tag 'p #:linebreak-proc (lambda (x) (detect-linebreaks x #:insert '())))) ◊(define (root . elements) (make-txexpr 'root null (decode-elements elements #:txexpr-elements-proc mk-para #:string-proc (compose smart-quotes smart-dashes)))) ``` The main difference from the code in `decode.rkt` is that I'm trying to use `'()` as the tag to insert in place of a line-break instead of `'(br)`. However, this causes a contract violation because `'()` is not a valid X-expression. Perhaps there should be some notion of a blank or empty X-expression that does not translated to anything?

Actually, looking at the X-expression docs I realize that the empty string "" is essentially a blank X-expression.

Actually, looking at the [X-expression docs](http://pkg-build.racket-lang.org/doc/xml/index.html#%28def._%28%28lib._xml%2Fprivate%2Fxexpr-core..rkt%29._xexpr~3f%29%29) I realize that the empty string `""` is essentially a blank X-expression.

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Blank or empty X-expression? #38