Added support for \not by k4b7 · Pull Request #140 · KaTeX/KaTeX

k4b7 · 2014-10-01T03:36:21Z

Addresses issue #29. Requires a Huxley test which I will try to add tomorrow. Here's a screenshot:

TODO:

rebase
switch the order so the solidus comes first in the span and is shifted over with CSS
figure out how to make firefox render \not{abc} correctly

k4b7 · 2014-10-01T03:43:26Z

This makes an assumption that group.value.body is a "rel". It really could be anything else. LaTeX and MathJax allow this. What they end up doing is placing the combining long solidus overlay glyph infront. Because this glyph already includes metrics that cause it to be rendered over the previous glyph, producing similar behaviour in these edge cases will require extra work.

k4b7 · 2015-06-26T15:34:30Z

We'll handle this using macros.

gagern · 2015-07-08T23:56:49Z

I don't see how this would be handled with macros, particularly the interaction with the atom type. Can you illustrate that idea? What would the \not macro look like?

k4b7 · 2015-07-09T00:10:30Z

I called the symbol the wrong thing, but I added a symbol for the long solidus. The not method in buildTree.js places one the long solidus after the inner symbol. It seems like a we could have a macro like \def\not#1{\longSolidus #1}. I just made up \longSolidus so maybe this isn't possible.

gagern · 2015-07-09T00:39:44Z

\def\not#1{\longSolidus #1} could almost be abbreviated to \let\not=\longSolidus except for the fact that \not{ab} is essentially \longSolidus{a}b which shouldn't make a difference. In LaTeX the definition of \not is \not=\mathchar"3236 and it is of type \mathrel. Looking at it this way, just your modifications to symbols.js should be sufficient to emulate LaTeX. Anything more fancy might be well intended, but actually contrary to how LaTeX does things, leading to incompatibilities.

k4b7 · 2015-07-09T00:43:06Z

In that case I'm going to re-open this.

sophiebits · 2015-07-15T14:20:26Z

Maybe-stupid question: why is this its own command type instead of just being one of the supported symbols?

k4b7 · 2015-07-15T14:31:21Z

@spicyj the \not glyph gets rendered after the rel that follows it in the source code so there needs to be some processing in buildTree.js (now buildHTML.js) to handle this. The macro I was suggesting in a previous comment should've been \def\not#1{#1 \longSolidus}. Sorry about the confusion.

sophiebits · 2015-07-15T14:41:19Z

Oh! I see.

gagern · 2015-07-15T21:49:01Z

But if \longSolidus overlaps the preceding character, then it behaves differently from the \not in LaTeX. In particular it will be aligned to the right edge of the group it affects, not the left edge. Perhaps we should add kernings so that the glyph is shifted to affect the following character? Or edit the font to achieve that?

k4b7 · 2015-07-15T22:17:48Z

@gagern because the \longSolidus occurs after the inner in the span it should already be right aligned. That glyph has funky metrics which shift it to the left by its width.

gagern · 2015-07-15T22:25:54Z

… it should already be right aligned.

Yes, and that's not consistent with TeX. In LaTeX, \not{abc} will essentially be {\not a}bc, while your {abc}\longSolidus would look like ab{\not c}. Sure, with multi-character groups we could split up the group and make this a\longSolidus bc, but the same problem holds for symbols of different widths, and for more complicated things in that group following the \not.

k4b7 · 2015-07-15T22:35:14Z

@gagern sorry, reading too quickly. I can flip the order and shift it forward.

k4b7 · 2015-09-26T00:04:17Z

In the case where there isn't a "not" version of whatever's in the body, I'll add the solidus in manually. This is what MathJax does:

<math xmlns="http://www.w3.org/1998/Math/MathML"> <mrow class="MJX-TeXAtom-REL"> <mpadded width="0"> <mtext>⧸</mtext> </mpadded> </mrow> <mrow class="MJX-TeXAtom-ORD"> <mi>a</mi> <mi>b</mi> <mi>c</mi> </mrow> </math>

k4b7 · 2015-09-26T00:39:37Z

The order is correct now. It's too bad firefox doesn't want to render it correctly.

xymostech · 2015-09-26T01:31:56Z

@kevinbarabash do you know why that is? Is it just failing to render the font correctly or something?

k4b7 · 2015-09-26T01:59:56Z

@xymostech I'm not sure. It renders everything correctly except for \not{abc}. For some reason the solidus is missing in this case.

sthoch · 2016-02-23T10:28:30Z

The solidus is there in my Firefox 44.0.2 (OS X 10.9.5).

k4b7 · 2016-02-23T22:20:03Z

@sthoch this pull request is to add it as a combining mark.

sthoch · 2016-02-29T10:14:30Z

Sorry, let me clarify: If I take your PR and use it to render \not{abc} with my Firefox, the solidus is there and not missing. I thought that was the problem.

k4b7 · 2016-02-29T16:15:59Z

@sthoch I didn't realize that you had tried this pull request out. I'll give it another try. It might have been a problem with the specific version of Firefox that I was using. What version are you using?

sthoch · 2016-02-29T16:33:27Z

Firefox 44.0.2 (OS X 10.9.5).

k4b7 · 2017-07-03T01:12:01Z

        groups.push(buildGroup(group, options));
    }
+
+    // TODO(kevinb): combine \\not with mrels and mords


MathJax combines \\not with certain relation operators and outputs the combined HTML entity inside an <mo> and for mords, it puts the HTML entity for not after the identifier inside an <mi>.

k4b7 · 2017-07-03T01:19:31Z

I've changed the approach significantly. Instead having a specific not group type and \\not function, buildExpression processes \\not groups and makes necessary changes to the following group.

I left a number of TODOs for subsequent PRs.

k4b7 · 2017-07-03T01:27:15Z

k4b7 · 2017-07-03T01:29:53Z

The handling of \\not with ords can definitely be improved, but it seems like a bit of an edge case as \\cancel is a better option for ords.

k4b7 · 2017-07-03T01:39:00Z

+    // Process \\not commands within the group.
+    // TODO(kevinb): Handle multiple \\not commands in a row.
+    // TODO(kevinb): Handle \\not{abc} correctly.  The \\not should appear over
+    // the 'a' instead of the 'c'.


I'll take care of these in a separate PR.

k4b7 · 2017-07-09T00:17:50Z

@gagern could you have another look at this?

to encourage other people with push access to review

k4b7 · 2017-08-12T23:58:12Z

Looks like I'll have to update the screenshots for this.

edemaine

LGTM. One typo in the comments. And need to fix the screenshots (and maybe run the --diff option to make sure changes are OK).

edemaine · 2017-08-20T18:17:01Z

+            // \u0338 is a combining glyph so we could reorder the children so
+            // that it comes after the other glyph.  This works correctly on
+            // most browsers except for Safari.  Instead we absolutely position
+            // the glyph and set it's right side to match that of the other


it's -> its

Can this same approach be used for #802 and #735?

It could almost be used for those but those accents are centered horizontally over their contents which complicates matters.

edemaine

I guess the screenshots fixed themselves? Anyway, thanks for revitalizing this old PR, @kevinbarabash! A very useful feature.

edemaine · 2017-08-23T16:35:02Z

For some reason I'm unable to actually merge this. Feel free to do so if you can...

k4b7 · 2017-08-23T17:10:29Z

For some reason I'm unable to actually merge this. Feel free to do so if you can...

@edemaine the branch needed to be updated. Do you see an "Update branch" in your UI?

edemaine · 2017-08-23T18:12:32Z

I did, but it wasn't clickable, which I hadn't seen before. Presumably a temporary glitch. Anyway, glad you fixed it.

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gagern mentioned this pull request Jun 26, 2015

Restructure functions, environments, symbols #262

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Added support for \not

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fix grammar in comment

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