Double \prec as a single symbol?

Question

We have < and \ll. What about double \prec, i.e. something like \prec\prec but with spacing as in \ll?

Remark. I could not find an answer in http://detexify.kirelabs.org/classify.html or http://www.ctan.org/tex-archive/info/symbols/comprehensive/. I am not interested, how to construct this symbol from two \prec's (I know how to reduce the distance), but I am searching for a symbol from some package, even so strange as MnSymbol.

Answer 1

The mathb font (from mathabx) has an \llcurly and a \ggcurly symbols. Here is how to use them without loading the whole package:

\documentclass[12pt]{article}
\usepackage[utf8]{inputenc}

\DeclareFontFamily{U}{mathb}{\hyphenchar\font45}
\DeclareFontShape{U}{mathb}{m}{n}{
<-6> mathb5 <6-7> mathb6 <7-8> mathb7
<8-9> mathb8 <9-10> mathb9
<10-12> mathb10 <12-> mathb12
}{}
\DeclareSymbolFont{mathb}{U}{mathb}{m}{n}
\DeclareMathSymbol{\llcurly}{\mathrel}{mathb}{"CE}
\DeclareMathSymbol{\ggcurly}{\mathrel}{mathb}{"CF}
\begin{document}

\[ a \llcurly b \quad a \ggcurly b \]

 \end{document} 

Answer 2

The unicodes are U+2ABB and U+2ABC. Here are some examples with the fonts I am having available (in order of increasing uglyness):

% arara: lualatex

\documentclass{article}
\usepackage{unicode-math}
\newcommand*{\test}{\ensuremath{\prec\Prec\Succ\succ}}

\begin{document}
    \setmathfont{code2000.ttf}\test

    \setmathfont{xits-math}\test

    \setmathfont{asana-math}\test

    \setmathfont{quivira.otf}\test

    \setmathfont{symbola.ttf}\test

    \setmathfont{MathCadUniMath.otf}\test

    %\setmathfont{cambria-math}\test % not on my system
\end{document}

Answer 3

Here's a homemade construction.

\documentclass{article}
\usepackage{graphicx}
\def\pprec{\mathrel{\scalebox{.9}[1]{$\prec$}\mkern-5mu%
  \scalebox{.4}[1]{$\prec$}\mkern-5.5mu\scalebox{.4}[1]{$\prec$}}}
\begin{document}
$a \pprec b$
\end{document}