[Tex/LaTex] How to use \lll properly

Question

I need the symbol <<< (left rotation). Now from TexStudio help, I found it as \lll. But when I use it, I get an error Undefined control sequence ... \lll. How to fix it?

Answer 1

Just for fun, a poor man's solution for \lll and \ggg:

\documentclass{article}
\usepackage{amssymb}

\makeatletter
\newcommand*{\pmlll}{%
  \mathrel{%
    \mathpalette\@lllggg<%
  }%
}
\newcommand*{\pmggg}{%
  \mathrel{%
    \mathpalette\@lllggg>%
  }%
}
\newcommand*{\@lllggg}[2]{%
  % #1: math style
  % #2: symbol
  \sbox0{$\m@th#1#2$}%
  \copy0 %
  \kern-.6\wd0 %
  \copy0 %
  \kern-.6\wd0 %
  \copy0 %
}
\makeatother

\begin{document}
\[ a \lll b \ggg c ^{d \lll e \ggg f} \]
\[ a \pmlll b \pmggg c ^{d \pmlll e \pmggg f} \]
\end{document}