Why are these @defthing blocks typeset incorrectly?

[Sage Gerard]

I attached an image showing the rendered output of https://github.com/zyrolasting/xiden/blob/master/docs/reference/settings.scrbl#L48

I create an application to `(defthing)` as a datum due to circumstances in the surrounding code. The hacky part being `get-contract-datum`, which tries to produce a datum usable as a contract expression. I'm assuming that this leaves no whitespace to preserve, so how do I modify a syntax object to include space in desired spots?

~slg

[Sorawee Porncharoenwase]

Caution: I haven’t tried your code yet.

I think Scribble uses source location equipped with syntax objects to figure out spacing. Since you generate stuff on the fly, there’s no source location, so the rendered text is screwed up.

An idea I have (which might not work) is to use write / pretty-write on the generated code to a string port, and then read-syntax it back. That way, you get the source locations correctly.

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[Philip McGrath]

I have encountered this problem. I don't have a real solution, but maybe my hacky solution will be good enough.

On Wed, Sep 23, 2020 at 7:37 PM Sorawee Porncharoenwase <sorawe...@gmail.com> wrote:

I think Scribble uses source location equipped with syntax objects to figure out spacing. Since you generate stuff on the fly, there’s no source location, so the rendered text is screwed up.

This is indeed the explanation. My hacky solution (you can see it here) is to build up term for Scribble to typeset—the equivalent of what you do here, I think—using `syntax` rather than `quasiquote`. IIRC (I haven't touched this code in a while), it didn't work to use `quasisyntax`/`unsyntax`, so I used `define/syntax-parse` to bind pattern variables to the generated sub-terms. This way, Scribble picks up the source locations from the template and uses spaces as it should.

This is a hack, though: in my case, I'm building a `let*` expression with potentially several binding pairs, and they will run off the margin of the page. There are probably various other problems: I remember this code being a bit annoying to write.

-Philip

 

[Sage Gerard]

I opted for the read-syntax based solution. For those reading, it's convenient to use `replace-context` from `syntax/strip-context` to donate lexical info.

The form of the transformer I used is:

@(define-syntax (reformat stx)

  (replace-context stx

    (read-syntax #f (open-input-string (with-output-to-string

      (lambda () (pretty-write `(begin . [...]))))))))

~slg

‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐

On Wednesday, September 23, 2020 8:07 PM, Philip McGrath <phi...@philipmcgrath.com> wrote:

I have encountered this problem. I don't have a real solution, but maybe my hacky solution will be good enough.

On Wed, Sep 23, 2020 at 7:37 PM Sorawee Porncharoenwase <sorawe...@gmail.com> wrote:

I think Scribble uses source location equipped with syntax objects to figure out spacing. Since you generate stuff on the fly, there’s no source location, so the rendered text is screwed up.

This is indeed the explanation. My hacky solution (you can see it here) is to build up term for Scribble to typeset—the equivalent of what you do here, I think—using `syntax` rather than `quasiquote`. IIRC (I haven't touched this code in a while), it didn't work to use `quasisyntax`/`unsyntax`, so I used `define/syntax-parse` to bind pattern variables to the generated sub-terms. This way, Scribble picks up the source locations from the template and uses spaces as it should.