From: Frédéric WANG <fred.wang@free.fr>

Date: Mon, 25 Mar 2013 10:25:54 +0100

Message-ID: <51501822.2000307@free.fr>

To: www-math@w3.org

Date: Mon, 25 Mar 2013 10:25:54 +0100

Message-ID: <51501822.2000307@free.fr>

To: www-math@w3.org

Thank you David and Daniel. My question was not really about how to implement the stretching but about the markup. The choice <mo stretch="true">=</mo> seems the most natural (and preserves the semantics of the diagram). It is used by LaTeXML and the MathJax extension. Since I don't see constructions for stretchy equal sign in Gecko or the STIX Open Type Math table, I wanted to be sure that everybody agree about that choice, and font designers and MathML implementers do the necessary to make the equal sign extendible. On 25/03/2013 10:10, Daniel Marques wrote: > I agree with David that using the equal sign has some implications. For > example, the distance of the two horizontal lines might not be the desired > one. Using the stretchy part of the double arrow or the box drawing have > the extra advantage that the parallel vertical bars (and maybe diagonal) > are also available and consistently drawn. > > Dani from WIRIS > > > -----Original Message----- > From: David Carlisle [mailto:davidc@nag.co.uk] > Sent: sábado, 23 de marzo de 2013 17:57 > To: www-math@w3.org > Subject: Re: Stretchy equal sign for commutative diagrams > > On 23/03/2013 15:02, Frédéric WANG wrote: >> Hi all, >> >> We are implementing the AMScd extension in MathJax: >> >> https://github.com/mathjax/MathJax/issues/420 >> >> and one horizontal stretchy operator that is needed is the character >> for two parallel horizontal bars. We use the equal sign "=" and it >> seems that LaTeXML does the same. >> >> I'm wondering if others have considered this operator and whether they >> used a different Unicode code point for that. The equal sign is not >> stretchy by default (that makes sense) and I don't see constructions >> in the Open Type Math table of e.g. the STIX fonts. >> This is not available in Gecko either. That's probably not hard to >> implement (one could repeat the equal sign or use the middle glyphs >> available for the "Double Right Arrow"), but I just want to coordinate >> with other projects and keep things consistent. >> > > I suppose U+2550 (from the box drawing block) is another possibility but > using an equals or an arrow part is more likely to blend in with other > arrows used I'd guess. AMScd itself I think doesn't use a font glyph at > all for this but uses a rule (I'm not sure that's relevant here though, I > think you'd want a character and stretchy attribute for MathML. > > David > > -- Frédéric Wang maths-informatique-jeux.com/blog/fredericReceived on Monday, 25 March 2013 09:30:01 GMT

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