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Related: Finishing math with a period

I believe of the two options

\[|f(x)-(y)|<\epsilon\text{.}\]

or

\[|f(x)-(y)|<\epsilon.\]

the first one is correct. However, a problem that was brought up (link above) is the kerning between the symbol before the period (e.g. a letter Y) and the period itself.

I came up with a funky solution, and my question is to ask the TeX community for a better(?) solution. I say better(?) because it's all subjective; however in my opinion a better solution would use less computation time or use non-LaTeX primitive TeX commands even if the time saved is in the order of milliseconds.

My proposed solution is the following:

\newcommand{\TP}{.\sbox0{$.$}\kern-1.819\ht0\rlap{\color{white}\rule{1.006\ht0}{1.006\ht0}}\kern1.819\ht0\llap{.}}

A downside of this solution is that a color package must be utilized to generate the "white" box which is designed to cover the correctly-kerned math-period so that the text-period can be placed on top. I'm also pretty sure \rlap and \llap are not TeX primitives so there's that too.

EDIT(1) It's been two months, and I think I stumbled on a more aesthetic solution. I also now think \rlap and \llap are indeed TeX primitives because they are mentioned in the TeXbook by Donald Knuth.

\newcommand{\TP}{\kern1.11112pt\llap{.}\kern0pt}

Alberto Takase
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  • Traditionally, there’s no period at the end of a display equation (although there could be in inline text). If you really want one, use \textnormal{.}. If you don’t like the kerning, add \kern-0.1pt\textnormal{.}.or whatever value looks best to you. – Davislor Dec 29 '20 at 06:05
  • Or maybe wrap it in \mathpunct. – Davislor Dec 29 '20 at 06:46
  • @Davislor I never considered \mathpunct I will do some testing with that; much thanks! – Alberto Takase Dec 29 '20 at 07:10
  • I found that \mathpunct{\text{.}} still does not kern properly. It would have been such a nice solution. – Alberto Takase Dec 29 '20 at 07:26
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    don't use color white to hide things, it fails miserably if the document is not printed on white or if sections cut and pasted. It is best to avoid sentence punctuation in displays but if it really can not be avoided separate it from the math with a large space such as \quad Inter-letter kerning should not be an issue at all here. – David Carlisle Dec 29 '20 at 11:03
  • @DavidCarlisle (1) I learned standard printers don't print white. (2) Here Can we get maths in PDFs that can be copy-pasted and screen-read? solves the copy paste issue and adds a visial disability support that I am happy to have learned about. (3) My "correct-kerning" solution is also for inline math. Even if the usage in display math will likely be rare, it is nice to have the option. Thank you for your comment; I learned much because of it. – Alberto Takase Dec 29 '20 at 16:25

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