A problem about typesetting Mathematica code

Question

I want to typesetting the words as below:

My code:

\documentclass[b5paper,UTF8]{article}
\usepackage{graphicx}                
\usepackage{geometry}               
\usepackage{fancyhdr}
\usepackage{times}
\geometry{left=2cm,right=2cm,top=2.8cm,bottom=2.5cm}
\begin{document}
\noindent \textsf{\textbf{4. Avoid inefficient patterns, construct efficient patterns}}
4.1. Rule-based programming can be both very fast and very slow, depending on how you
build your structures and rules, but in practice it is easier to inadvertently make 
it slow. It will be slow for rules which force the pattern-matcher to make many a 
priory doomed matching attempts, for example by under-utilizing each run of the
pattern- matcher through a long list (expression). Sorting elements is a good example: 
list / / . { left___ , x _ , y _ , right ___ }/ ; x $>$ y :  $>$ { left, y, x, right } - has a cubic complexity in the size of the list.
\end{document}

However, the main problem is

list \/ \/ . \{ left\_\_\_ , x \_ , y \_ , right \_\_\_ \}\/ \; x $>$ y \: $>$ \{ left, y, x, right \} - has a cubic complexity in the size of the list.