\left \right give inproper vertical spacing in fouriernc font

Here is a minimalist example

\documentclass{article}
\usepackage{fouriernc}
\begin{document}
$\mathbb{E} [x \mid y ]$
\end{document}


The result looks like this:

But if I use \left and \right, i.e., \mathbb{E} \left[x \mid y \right], then the result would look like this:

The horizontal spacing looks fine. However, the brackets are also vertically shifted down a bit. Previously the bracket top is a bit higher than E, but now the top is aligned with the top of E.

Is it possible to just use the horizontal spacing without changing the vertical spacing with \left and \right?

• I've taken the liberty of making your example truly minimal. Feel free to revert. – Mico Mar 24 at 15:31
• @Mico That looks very good ^ – Nathan Explosion Mar 24 at 15:57

1 Answer

The character used is the same, because it fits the requirements for \left and \right size. The difference is that the brackets [] are not symmetric with respect to the math axis and \left\right instead places the obtained fences exactly so the character extends above the math axis as much as below.

In the picture below, \mathaxis produces a line that sits exactly over the math axis.

\documentclass{article}
\usepackage{fouriernc}

\newcommand{\mathaxis}{%
\vrule width 1em
height \dimexpr\fontdimen22\textfont2+0.2pt \relax
depth \dimexpr-\fontdimen22\textfont2+0.2pt \relax
}
\begin{document}

$\mathbb{E} [x \mid y ] \mathaxis$

$\mathbb{E} \left[x \mid y \right] \mathaxis$

\end{document}


Another reason for not using \left\right unless really needed.

• It is strange that the problem will not happen if we use the default computer modern font. – Nathan Explosion Mar 24 at 18:21
• @NathanExplosion The parentheses in CM have the same height above the math axis as below. – egreg Mar 24 at 21:12