On Sat, 29 May 2010, Yury G. Kudryashov wrote:

> Taco Hoekwater wrote:
>
>> Yury G. Kudryashov wrote:
>>> Hi!
>>> 
>>> I try the following:
>>> 
>>> \starttext
>>> $∫_a^b \int_a^b$
>>> \stoptext
>>> 
>>> In the first case, the integral sign is below the text. Should I use
>>> another font, or is it possible to fix with the default one?
>> 
>> It is possible to fix this. The reason for the odd placement is that the
>> 'math code' of ∫ is not set up properly (and it probably isn't either
>> for some other bare Unicode characters). To fix the hard way, add this
>> at the top of your input file:
>> 
>> \Umathcode `∫ = 1 0 `∫ % 1 == \mathop, 0=fam0, ∫=glyph
> Is there any documentation on char-def.lua file format? If I'll understand 
> it, I'll send a patch for the symbols I use.

Not a complete documentation, but some explanation is here

https://www.tug.org/members/TUGboat/tb30-2/tb95mahajan-cmath.pdf

> Currently I have no idea why the following strings in char-def don't work.
>
> [0x222B]={
>  adobename="integral",
>  category="sm",
>  cjkwd="a",
>  description="INTEGRAL",
>  direction="on",
>  linebreak="ai",
>  mathspec={
>    { class="nothing", name="intop" },
>    { class="limop"  , name="int"   },
>  },
>  unicodeslot=0x222B,
> },
>
> Replacing mathspec=... with mathclass="limop", mathname="int" seems to work 
> (copied from n-ary summation).
>
> BTW, in both solution ∫_a acts like \int\limits_a, not \int_a.

In plain TeX, this is taken care by

\mathchardef\intop="1352 \def\int{\intop\nolimits}

Can I do the same in luatex without active characters?

\Umathchardef\INTOP=1 0 `∫
\def\INT{\INTOP\intlimits}

\catcode`∫=\active
\let ∫=\INT

\starttext
$∫_a^b$

$\displaystyle ∫_a^b$
\stoptext

Aditya