Double arrow with text over it that extends to fit text (that is, a "\xRightarrow")

Question

I know it's possible to have \xrightarrow (text), but if I try to do \xRightarrow (text) I get an error each time. Does anybody know if it's a syntax error or if there is a other way to produce the \Rightarrow with text above?

Answer 1

Just taking the definition of \xrightarrow and replacing r by R :

\documentclass{article}
\usepackage{amsmath}


\makeatletter
\newcommand{\xRightarrow}[2][]{\ext@arrow 0359\Rightarrowfill@{#1}{#2}}
\makeatother

\begin{document}

% To create a single arrow with text above, use lowercase "r".
$\xrightarrow{\mathit{hello}}$

% To create a double arrow with text above, use uppercase "R".
$\xRightarrow{\mathit{hello}}$


\end{document}

Answer 2

\documentclass{article}
\usepackage{mathtools}
\begin{document}

$\xrightarrow{\text{hello}}$
$\xRightarrow{\text{hello}}$

\end{document}

Answer 3

You can also use underset and overset:

$\underset{\text{hello}} \longrightarrow$

$\overset{\text{hello}} \longrightarrow$

$\underset{\tiny\text{hello}} \longrightarrow$

$\overset{\tiny\text{hello}} \longrightarrow$