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    • CommentRowNumber1.
    • CommentAuthorAndrew Stacey
    • CommentTimeJun 5th 2009

    I've just (or am just about to) put a load of arrowheads in the SVG Sandbox.

    How do these look? Are they okay? Should there be more (if so, which?)? Are some of these too strange to be in the "official" list?

    The list is based on what the xy package offers as "standard" arrowheads.

    • CommentRowNumber2.
    • CommentAuthorTobyBartels
    • CommentTimeJun 7th 2009
    Maybe this is a separate topic from arrowheads, but it would be nice to have (the thing like) ‘-|->’ for relations and profunctors.
    • CommentRowNumber3.
    • CommentAuthorAndrew Stacey
    • CommentTimeJun 9th 2009

    I'm not sure what context you want this in. Do you want it as a type of arrow in a big diagram, as essentially a virtual entity in an equation (used much as \to or \mapsto) - or both? The former is clearly an SVG thing, if the latter do you want it as an SVG that is embedded or as a hacked together entity?

    If you want an SVG in equations then I can figure one out for you, but I need something a little more specific than -|->! Do you have a nice example in a picture/document somewhere that you can send me?

    • CommentRowNumber4.
    • CommentAuthorAndrew Stacey
    • CommentTimeJun 9th 2009

    By the way, what do you think of the arrowheads?

    • CommentRowNumber5.
    • CommentAuthorTobyBartels
    • CommentTimeJun 9th 2009
    • (edited Jun 9th 2009)
    Yes, I like the arrowheads. And I was thinking of ‘-|->’ in big SVG diagrams; getting it into small iTeX diagrams is a struggle on another front. (^_^)
    • CommentRowNumber6.
    • CommentAuthorAndrew Stacey
    • CommentTimeJun 9th 2009

    So you mean it as like a long arrow in a commutative diagram. Okay, in that case what is it exactly? Is it a normal arrow with an orthogonal line through the middle? Or is the line somewhere else (in your latest post you write '-|>' rather than '-|->')? Either way, shouldn't be hard to mock up.

    • CommentRowNumber7.
    • CommentAuthorTobyBartels
    • CommentTimeJun 9th 2009
    This comment is invalid XHTML+MathML+SVG; displaying source. <div> Oops, typo! Fixed.<p>Try this (as plain TeX) to see what it should look like:<pre>\input xy<br/>\xyoption {all}<br/><br/>\bye</pre></p> </div>
    • CommentRowNumber8.
    • CommentAuthorTobyBartels
    • CommentTimeJun 9th 2009
    (H'm, that looked just fine on preview, but now it looks like your math code is trying to take over. Anyway, mouse over to see the formula; cut and paste seems to work too.)
    • CommentRowNumber9.
    • CommentAuthorAndrew Stacey
    • CommentTimeJun 9th 2009

    Looks easy enough.

    It'd be better style to define a new arrow stem so that you'd get that by typing

    \xymatrix{ C \ar@{{}{-|-}>}[r] & D}
    

    but that's just me being pedantic.

    • CommentRowNumber10.
    • CommentAuthorTobyBartels
    • CommentTimeJun 9th 2009
    Definitely, but I just went for the quick and dirty method to get you a picture.
    • CommentRowNumber11.
    • CommentAuthorMike Shulman
    • CommentTimeJun 10th 2009

    I usually make it with \xymatrix{ A \ar[r]|-@{|} & B }.

    • CommentRowNumber12.
    • CommentAuthorAndrew Stacey
    • CommentTimeJun 10th 2009

    Okay, mock-up is now on the SVG Sandbox. Trick is to "break" a path at it's mid-point and specify a marker-mid attribute for the path.

    • CommentRowNumber13.
    • CommentAuthorTobyBartels
    • CommentTimeJun 10th 2009
    I didn't realise that one could do that, Mike. Thanks, that makes a lot of sense.

    Andrew, all of those arrow parts look good! The diagram ‘just for [me] and Mike’ does not look good, since the arrow is too high compared to the letters (at least as it looks to me). But that's probably because the letters should be part of the SVG diagram, so I don't blame you (^_^).

    • CommentRowNumber14.
    • CommentAuthorTobyBartels
    • CommentTimeJun 10th 2009
    • (edited Jun 10th 2009)
    I just realised, looking at the name doubleArrow, that we also want double (and triple?) arrows where the shaft is doubled, as well as where the entire arrow is doubled. (Like ‘?’ and ‘?’, respectively.)
    • CommentRowNumber15.
    • CommentAuthorAndrew Stacey
    • CommentTimeJun 10th 2009

    Yes, I didn't take any time to get the letters and arrow in perfect alignment so ignore that!

    As for the doubled and tripled arrows, just hang on a little longer. I've been working on a conversion program and I'm almost ready for alpha testers.

    (Another one to add to my list of annoyances about this forum: I see "Like '?' and '?', respectively.". Presumably you're typing in one charset and it isn't being translated correctly to whatever charset I'm viewing the page in.)

    • CommentRowNumber16.
    • CommentAuthorTobyBartels
    • CommentTimeJun 10th 2009
    Sign me up for testing then!

    (Right, I forgot about that! It's worse than you think: the HTML served by the page simply has question marks, nothing more. But the preview shows things correctly! Anyway, they should be $\Rightarrow$ and $\rightrightarrow$.)

    • CommentRowNumber17.
    • CommentAuthorAndrew Stacey
    • CommentTimeJun 11th 2009
    This comment is invalid XML; displaying source. <p>What are you typing to try to generate those letters? Are you using the maths facility? Let's try: &#40;\Rightarrow&#41; and &#40;\rightrightarrow&#41;. Or are you trying unicode characters ... <looks for character selector> ... bleugh, can't figure out where they are, or entities? Let's try: &rArr;.</p> <p>(I suppose I could go directly to the database and find your comment ...)</p>
    • CommentRowNumber18.
    • CommentAuthorTobyBartels
    • CommentTimeJun 13th 2009
    I'm typing the character directly. Firefox thinks that the character encoding is utf-8, so presumably that's how it's being sent. For purposes of preview, that's how it comes back, but the post itself has a question mark instead.

    But now that I think about it, does the preview even go to the server, or is it handled entirely on my side with Javascript? That could certainly explain how the preview and the post might fail to match.

    • CommentRowNumber19.
    • CommentAuthorAndrew Stacey
    • CommentTimeJun 13th 2009

    Without knowing a lot of what goes on here, I think that you're right. The preview facility is provided for by a plugin and that plugin has an ajax and a javascript component. I haven't looked at the scripts in detail, but the basis of their existence lends considerable support to your hypothesis.

    That's odd. I thought that I got the maths syntax correct in my post. Now it's displaying only the input. It took a couple of attempts before I remembered how I'd set up the LaTeX input so maybe the database didn't store my edits. Let's try again: \Rightarrow and \rightrightarrow.

    Is the character set issue easy to fix, do you know? Is it extremely annoying, or can you live with it as it is?

    • CommentRowNumber20.
    • CommentAuthorAndrew Stacey
    • CommentTimeJun 13th 2009

    Oh, \rightrightarrow does not parse. Looks like I ought to adapt my buggy script into a plugin for the forum. Then whenever I get a formula that doesn't parse, I can simply define my own macros so that it does!

    • CommentRowNumber21.
    • CommentAuthorTobyBartels
    • CommentTimeJun 13th 2009
    I can work around it, I just have to remember to. The only really annoying thing is that I must remember not to trust the preview.