是否可以从现代计算机中取出“总和”，从傅立叶中取出“括号”？

Question

代码在这里。另外我如何添加下支架来自傅立叶？

\documentclass[11pt,a4paper]{article}
\usepackage[english]{babel}
\usepackage[utf8x]{inputenc}
\usepackage{ucs}
\usepackage{amsmath}
\usepackage{amsfonts,theorem}
\usepackage{amssymb}
\usepackage{newtxtext}
\usepackage{newtxmath}

\DeclareSymbolFont{mdsymbols}     {OMS}{mdput}{m}{n}
\DeclareSymbolFont{mdlargesymbols}{OMX}{mdput}{m}{n}

\DeclareMathDelimiter{\lbrace}
   {\mathopen}{mdsymbols}{"66}{mdlargesymbols}{"08}
\DeclareMathDelimiter{\rbrace}
   {\mathclose}{mdsymbols}{"67}{mdlargesymbols}{"09}
\renewcommand{\textbraceleft}{%
  {\fontfamily{mdput}\fontencoding{OMS}\selectfont\char"66}}
\renewcommand{\textbraceright}{%
  {\fontfamily{mdput}\fontencoding{OMS}\selectfont\char"67}}
  \let\sum\relax
  \DeclareMathSymbol{\sum}{\mathop}{mdlargesymbols}{"50}

%\let\sum\relax
%\DeclareMathSymbol{\sum}{\mathop}{mdlargesymbols}{"50} % i want this from computer modern.

\begin{document}

\[\sum\] 
should come from computer modern.
\[ \left\{
\begin{array}
[c]{ccc}%
x & , & 0<x<1\\
\sin x & , & x\geqslant1\\
x^2 & , & x<0\\
\end{array}
\right. \]
braces from fourier.

\end{document}

Answer 1

请注意，这mdput指的是 MathDesign Utopia，而不是 Fourier。

\documentclass[11pt,a4paper]{article}
\usepackage[english]{babel}
\usepackage[utf8]{inputenc}
\usepackage{amsmath}
\usepackage{amsfonts,theorem}
\usepackage{amssymb}
\usepackage{newtxtext}
\usepackage{newtxmath}

\DeclareSymbolFont{cmlargesymbols}{OMX}{cmex}{m}{n}
\DeclareSymbolFont{mdsymbols}     {OMS}{mdput}{m}{n}
\DeclareSymbolFont{mdlargesymbols}{OMX}{mdput}{m}{n}

\DeclareMathDelimiter{\lbrace}{\mathopen}{mdsymbols}{"66}{mdlargesymbols}{"08}
\DeclareMathDelimiter{\rbrace}{\mathclose}{mdsymbols}{"67}{mdlargesymbols}{"09}
\DeclareMathSymbol{\braceld}{\mathord}{mdlargesymbols}{"7A}
\DeclareMathSymbol{\bracerd}{\mathord}{mdlargesymbols}{"7B}
\DeclareMathSymbol{\bracelu}{\mathord}{mdlargesymbols}{"7C}
\DeclareMathSymbol{\braceru}{\mathord}{mdlargesymbols}{"7D}

\let\sum\relax
\DeclareMathSymbol{\sum}{\mathop}{cmlargesymbols}{"50}

%%% newtxmath changes the definition of \downbracefill and \upbracefill
%%% restore the default
\makeatletter
\def\downbracefill{$\m@th \setbox\z@\hbox{$\braceld$}%
  \braceld\leaders\vrule \@height\ht\z@ \@depth\z@\hfill\braceru
  \bracelu\leaders\vrule \@height\ht\z@ \@depth\z@\hfill\bracerd$}
\def\upbracefill{$\m@th \setbox\z@\hbox{$\braceld$}%
  \bracelu\leaders\vrule \@height\ht\z@ \@depth\z@\hfill\bracerd
  \braceld\leaders\vrule \@height\ht\z@ \@depth\z@\hfill\braceru$}
\makeatother

\let\textbraceleft\relax \let\textbraceright\relax
\DeclareRobustCommand{\textbraceleft}{%
  {\fontfamily{mdput}\fontencoding{OMS}\selectfont\char"66}}
\DeclareRobustCommand{\textbraceright}{%
  {\fontfamily{mdput}\fontencoding{OMS}\selectfont\char"67}}



\begin{document}

\[
\sum
\begin{cases}
x & 0<x<1\\
\sin x & x\geqslant1\\
x^2 & x<0\\
\end{cases}
+
\underbrace{ab+ac+ca}_{d}
\]

\end{document}