# Re: Stretchy equal sign for commutative diagrams

From: David Carlisle <davidc@nag.co.uk>
Date: Sat, 23 Mar 2013 16:56:50 +0000
Message-ID: <514DDED2.2050907@nag.co.uk>

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

Received on Saturday, 23 March 2013 16:57:17 UTC

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