TeX - LaTeX Asked on July 10, 2021
I am using auto-generated Latex code from CAS system. It uses mathrm{ln}
and {mathrm e}
.
The problem is the spacing between this and the letter before it, compared to when no mathrm
is used. The space is lost in the case with mathrm{ln}
Here is an example
documentclass[12pt]{book}
usepackage{amsmath}
usepackage{mleftright}
mleftright
begin{document}
[
4 {mathrm e}^{3 x}+3 mathrm{ln}left(x right)
]
[
4 e^{3 x}+3 lnleft(x right)
]
end{document}
Compiled with lualatex, gives
I prefer the second one. The space before mathrm e
has not changed. But the space before mathrm{ln}
was lost.
Why is that? Is it then not approrpiate to use mathrm
for ln
?
TL 2020
Your autogenerated code is bad, sorry. In
3mathrm{ln}left(xright)
there are three atoms, namely
3
of type Ordmathrm{ln}
of type Ordleft(xright)
of type InnerBetween two atoms of type Ord, TeX inserts no space.
To the contrary,
3lnleft(xright)
contains again three atoms, but with a big difference, namely
3
of type Ordln
of type Opleft(xright)
of type InnerTeX inserts a thin space (of the amount of thinmuskip
) between an Ord atom and an Op atom.
Sorry, but “garbage in, garbage out”. If the software is able to recognize the string ln
to be set in upright type, it could well take the initiative of outputting ln
instead of the wrong mathrm{ln}
.
By the way, also left
and right
are out of place. And it's quite interesting that “e” is translated into {mathrm e}
instead of the more correct mathrm{e}
(if you really insist into printing the Euler constant upright).
A fix.
documentclass[12pt]{book}
%usepackage{xparse} % not needed for LaTeX 2020-10-01 or later
usepackage{amsmath}
usepackage{mleftright}
mleftright
ExplSyntaxOn
NewCommandCopy{latexmathrm}{mathrm}
RenewDocumentCommand{mathrm}{m}
{
str_case:nnF { #1 }
{
{e}{e}
{i}{i}
{ln}{ln}
{log}{log}
{sin}{sin}
% ... add to the list
}
{ latexmathrm{#1} }
}
ExplSyntaxOff
begin{document}
[
4 {mathrm e}^{3 x}+3 mathrm{ln}left(x right)
]
[
4 e^{3 x}+3 lnleft(x right)
]
end{document}
For LuaLaTeX and unicode-math
, the workaround has to be different.
documentclass[12pt]{book}
%usepackage{xparse} % not needed for LaTeX 2020-10-01 or later
usepackage{amsmath}
usepackage{mleftright}
usepackage[mathit=sym,bold-style=ISO]{unicode-math}
setmathfont{Asana Math}[Scale=MatchLowercase]
setmainfont{Baskervaldx}[
UprightFont=*-Reg,
ItalicFont=*-Ita,
BoldFont=*-Bol,
BoldItalicFont=*-BolIta,
]
mleftright
ExplSyntaxOn
AtBeginDocument
{
NewCommandCopy{latexmathrm}{mathtextrm}
RenewDocumentCommand{mathtextrm}{m}
{
str_case:nnF { #1 }
{
{e}{e}
{ln}{ln}
{log}{log}
{sin}{sin}
% ... add to the list
}
{ latexmathrm{#1} }
}
}% end of AtBeginDocument
ExplSyntaxOff
begin{document}
[
4 {mathrm e}^{3 x}+3 mathrm{ln}left(x right)
]
[
4 e^{3 x}+3 lnleft(x right)
]
end{document}
Note that Baskervaldx.sty
is not the right choice when fontspec
is used.
Correct answer by egreg on July 10, 2021
In this case, ln
is what’s called a log-like operator.
You can use either ln
, operatorname{ln}
or mathop{mathrm{ln}}
to get spacing like log
. You can also add nolimits
if you don’t like how subscripts and superscripts get placed above and below in display mode.
If amsmath
did not already define it, you could write providecommandln{operatorname{ln}}
and then have a ln
command you could use in your source, and be able to tweak in one easy-to-find place.
Answered by Davislor on July 10, 2021
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