【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}

ewcommand{cev}[1]{
eflectbox{ensuremath{vec{
eflectbox{ensuremath{#1}}}}}}

　　Then use cev to create a small left arrow

　　An example is illustrated here.

documentclass{article}
usepackage{graphicx}

ewcommand{cev}[1]{
eflectbox{ensuremath{vec{
eflectbox{ensuremath{#1}}}}}}
egin{document}
[
h_t = [overrightarrow{h}_t, overleftarrow{h}_t], [vec{h}_t, cev{h}_t]
]
end{document}