Scribble abstraction to attach styles

[Shriram Krishnamurthi]

I'm having trouble with the type structure of Scribble and hoping someone can help me get this right.

Let's say I want to write content like this:

=====

@exercise{
@question{The expression @code{1 + 2} evaluates to}
@answer{
@itemlist[
@item{@code{2}}
@item{@code{3}}
@item{@code{4}}
]
}
}

=====

That is, an `exercise` contains within it a `question` and an `answer` (and maybe other parts). Each of those can contain compound content (text, code, itemlists...). In my (HTML) output I would like each of these to have their own class tags, so the structure looks like

<div class="exercise">
...
<div class="question">
...
</div>
...
<div class="answer">
...
</div>
...
</div>

I have set up styles as follows:

(define exercise-style (make-style "exercise" null))
(define question-style (make-style "question" null))
(define answer-style (make-style "answer" null))

What I'm trying to do is create the correct form of "pass-through" abstraction for the `exercise`, `question`, and `answer` functions that just attach the style and leave everything else alone: e.g.,

(define (exercise . t) (nested-flow exercise-style t))
(define (question . t) (nested #:style question-style t))

I have tried a whole bunch of things (`nested`, `nested-flow`, etc.) and cannot get anything to work correctly, consistently: each thing I try eventually results in a contract violation such as

make-nested-flow: contract violation
expected: block?
given: "\n"

TIA,
Shriram

[Alexander D. Knauth]

Would something like
(define (question . t) (apply elem #:style question-style . t))
work?

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[Alexander D. Knauth]

I just tried (nested #:style question-style t) and that worked. What got that to fail?
Also I should have tried elem with answer, not just question.

[Shriram Krishnamurthi]

Thanks for these replies. Sorry I'm only now getting to them: Google failed to notify me of them.

The problem with using (nested ...) is that it indents its content even when I don't use the 'inset style. Therefore, if I have (as I do)

@exercise{@question{...}}

everything in the exercise ends up nested one level, and the question ends up nested two levels. That's why I rejected the use of `nested` and was looking for alternate solutions.

How can I get `nested` to not indent? I have exactly what you suggested:

(define (exercise . t) (nested #:style question-style t))

(define (question . t) (nested #:style question-style t))

where

(define exercise-style (make-style "exercise" null))
(define question-style (make-style "question" null))

and this still leads to the indentation.

[Ben Lerner]

Probably a CSS fix: assuming you have something like this in your CSS preamble

div.question { padding-left: 2em; }

to cause the indentation, then something like this will disable the nested one:

div.exercise > div.question { padding-left: 0em; }

~ben

[Shriram Krishnamurthi]

Understood. But my understanding of the docs is that it shouldn't do
that in the first place.

[Matthias Felleisen]

Isn't it the whole point of styles to allow this kind of fixes? I am playing with similar fixes for TeX output. Scribble is an UNCOL and all UNCOLs fail a little bit at least -- Matthias

[Alexander D. Knauth]

I don’t know if there’s a better more general solution, but does this do what you want?
@(define exercise-style (make-style "exercise" (list (attributes '([style . "margin-left: 0em"])))))
@(define question-style (make-style "question" (list (attributes '([style . "margin-left: 0em"])))))
@(define answer-style (make-style "answer" (list (attributes '([style . "margin-left: 0em"])))))

[Shriram Krishnamurthi]

Of course it is. I can certainly hack my way around it using CSS. But
I'm wondering why the behavior doesn't match my reading of the docs:
did I misread, is the code broken, or are the docs broken? That's
really all I'm trying to figure out. (And if the code or docs are
wrong, then presumably someone who maintains them would like a bug
report.)

Shriram

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[Matthew Flatt]

I'll revise the docs to clarify that the default style is up to the
target environment. For HTML output, `nested` corresponds to
<blockquote>, and that (usually?) insets its content by default. For
Latex output, `nested` corresponds to a plain list environment, which
doesn't inset.

[Matthew Flatt]

And maybe helpful for the original question: Including `(alt-tag
"div")` in the property list of your styles produces <div> in the HTML
output instead of <blockquote>, which is more directly what you want
and avoids any default inset of <blockquote>.

At Thu, 21 May 2015 16:52:12 -0400, Shriram Krishnamurthi wrote: