Resize integral symbol in the same way of a delimiter

Question

This answer addresses the possible way to typeset a bigger integral sign, but one has to choose the right size of the symbol that better fits the situation.

My question is: why can't we resize the \int symbol as we usually do for common delimiters (), [] and \{\}?

By writing

\left\{ \left[ \left( stuff \right) \right] \right\}

delimiters are automatically sized with respect to stuff and the preceding/subsequent delimiter.

Why can't we write

\left \int \left\{ \left[ \left( stuff \right) \right] \right\} \right.

so that the \int symbol is automatically sized, too?

Answer 1

Opentype Math fonts can make use of the Integral extension character U+23AE

I'm not sure I like the result but this is Cambria Math with LuaLaTeX.

\documentclass{article}
\usepackage{unicode-math}
\setmathfont{Cambria math}

\begin{document}


\[
\Uleft\Udelimiter 0 0 "222B
\begin{pmatrix}
  1
\end{pmatrix}
\Uright.
\rightarrow
\Uleft\Udelimiter 0 0 "222B
\begin{pmatrix}
  1\\2
\end{pmatrix}
\Uright.
\rightarrow
\Uleft\Udelimiter 0 0 "222B
\begin{pmatrix}
  1\\2\\3\\4
\end{pmatrix}
\Uright.
\rightarrow
\Uleft\Udelimiter 0 0 "222B
\begin{pmatrix}
  1\\2\\3\\4\\5\\6
\end{pmatrix}
\Uright.
\]
\end{document}