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Unicode has three slots for integrals parts (U+23A0, U+23A1, U+23AE) which should enable to build extensible integrals. Some maths fonts (TeXGyrePagella, STIXTwoMath,…) provide these glyphs and a recipe in \int (U+222B) to stack them (like growing delimiters).

An easy way to use them would be

\[ \left\int ... \right. \]

but this can't work as the \int character is not a delimiter but an operator. So I tried to define

\def\extint{\Udelimiter"4 "0 "222B \relax}

to make an opening delimiter out of U+222B. This works but doesn't allow for limits to be added, a closing delimiter would be better… easy to do but clumsy to use, here is an example:

\documentclass{article}
\usepackage{amsmath}
\usepackage{unicode-math}
\setmathfont{texgyrepagella-math.otf}
\def\extint{\Udelimiter"5 "0 "222B \relax} % Closing delimiter
\begin{document}
\def\myformula{\frac{1-\sqrt{\sqrt{\sqrt{\sqrt{\sqrt{\sqrt{x}}}}}}}%
                    {1+\sqrt{\sqrt{\sqrt{\sqrt{\sqrt{\sqrt{x}}}}}}}}

[\left.\vphantom{\myformula}\right\extint_{a}^{b}\myformula,\symup{d}x]
\end{document}

and the output:

enter image description here

Note: the formula is stupid, any mathematician would just code \sqrt[64]{x} for the radical and use a normal integral, but this example shows that growing radicals work out of the box with unicode-math while growing integrals do not.

My question: I know that the ConTeXt people are working on this issue (luametatex), any hope for improvements for lualatex/unicode-math?

user202729
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Daniel Flipo
  • 2,059
  • Actually I don't think luametatex has anything to do with growing integral like this, but I could be wrong about this. – user202729 Oct 31 '22 at 16:24
  • I guess if you really want to typeset it you can do what you did (with a few macros to make it comfortable to use), but I don't think TeX the engine is designed that way, like "just use a normal integral sign" so I don't think Unicode-math will get this feature either. See also math mode - Big integral sign - TeX - LaTeX Stack Exchange – user202729 Oct 31 '22 at 16:29
  • I do not really want to typeset this formula, I just wonder why it is so complicated to use existing Unicode characters. Or is it that nobody ever used them with lualatex or xelatex? – Daniel Flipo Oct 31 '22 at 16:34
  • @user202729 Support for these extensible integrals, including to place limits on them, is supported in ConTeXt luametatex. I don't know any other application that supports them. Simple example. – mickep Oct 31 '22 at 16:39
  • @user202729 it got added to lmtx recently – David Carlisle Oct 31 '22 at 16:50
  • The Unicode integral pieces were "grandfathered" relics of pre-laser-printer composition. In the opinion of TeX's creator, such large integrals were neither good style nor needed. (This is merely a historical note, not a recommendation.) – barbara beeton Oct 31 '22 at 16:52
  • @barbarabeeton OpenType math fonts allow extensible integrals just like delimiters which do not require unicode slots for the bits – David Carlisle Oct 31 '22 at 17:26
  • @DavidCarlisle -- The OpenType mechanism is almost certainly more reliable than the Unicode pieces, but I did say that my comment was meant as a historical note. Those pieces were designed for line printers. Who uses a line printer these days? – barbara beeton Oct 31 '22 at 17:44
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    @barbarabeeton I'm sure egreg isn't ready to upgrade to a dot matrix printer yet – David Carlisle Oct 31 '22 at 18:52
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    @DavidCarlisle -- Some of us still use quills and carbon ink. – barbara beeton Oct 31 '22 at 18:57
  • Forgive my ignorance, but aren't U+23A0 and U+23A1 \rparenlend and \lbrackuend respectively, and not integral extension symbols? – Apoorv Potnis Jul 14 '23 at 18:51

0 Answers0