I have a function f
that I want to restrict to a certain sub-domain of the domain it has been originally defined for. Usually, in mathematics this is illustrated by a vertical bar followed by the restricted set in the lower right of the function symbol. E.g. usually I write
f_{\mid A}
which means f
restricted to the set A
.
Unfortunately, I have a sequence of functions f_i
that has already a subscript. If I write
f_{i_{{\mid A}}}
I do net get an LaTeX error, but the result is semantically wrong. \bar A
is not a subscript of i
which happens to be a subscript of f
, but \mid A
is a subscript of f_i
. Especially, the font size of {\mid A}
should not be smaller than the size of i
, but have the same size.
However, if a write
{f_i}_{\mid A}
(which btw would be semantically correct) I get a "double subscript error".
Alternatively, I could write
f_{i \; \mid A}
and get the correct font size for \mid A
but it is placed too high. \mid A
should be below i
.
MWE
\documentclass{article}
\usepackage[TS1,T1]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage{lmodern}
\begin{document}
\begin{equation}
{\hat{f}_i}_{\mid A}
\end{equation}
\end{document}
As I have already found out, the problem occurs only with the accent above f
. But I need the accent there.
f_{\bar{A}}
,f_{i_{\bar{A}}}
... ?\mid A
should be belowi
.” But should it really? The convention I’ve seen before is that double subscripts are collapsed and put on the same subscript level, at the same size, and sometimes separated by a comma/semicolon.\bar
in place of\mid
.