【569】LaTex, arrows over letters

　　There are two ways to implement this effect.

1. \overleftarrow, \overrightarrow

　　This method is easy to use, but it always makes a big spacing between two lines and different letters.

2. \vec

　　This method can create a small right arrow, but it cannot generate the left arrow over letters

3. improved method

\usepackage{graphicx}
\newcommand{\cev}[1]{\reflectbox{\ensuremath{\vec{\reflectbox{\ensuremath{#1}}}}}}

　　Then use \cev to create a small left arrow

 

　　An example is illustrated here.

\documentclass{article}
\usepackage{graphicx}
\newcommand{\cev}[1]{\reflectbox{\ensuremath{\vec{\reflectbox{\ensuremath{#1}}}}}}
\begin{document}
\[
h_t = [\overrightarrow{h}_t, \overleftarrow{h}_t], [\vec{h}_t, \cev{h}_t]
\]
\end{document}