How to import a few symbols from `fdsymbol`?

Question

I saw this question: Importing a Single Symbol From a Different Font and I try to figure out how I do it for fdsymbol to the symbols: \neswarrow, \leftrightarrow, \nwsearrow, \updownarrow

I can't load the fdsymbol package because it's destroy some of the amsmath symbols :-(...

Can you help me please?

Thank you!

Answer 1

In fdsymbol.sty there are no slot numbers and one has to count manually.

One finds

\fdsy@setslot{0}
\fdsy@DeclareSymbol{\rightarrow}{arrows}{\mathrel}

which means \rightarrow is at slot 0 of the arrows symbol font. Looking for your desired symbol and counting yields that

• \leftrightarrow is at slot 16
• \updownarrow is at slot 17
• \neswarrow is at slot 18
• \nwsearrow is at slot 19

We also find

\DeclareSymbolFont{arrows}{U}{FdSymbolC}{m}{n}

Thus we need also to copy the font definitions for this font and undefine \updownarrow.

You may want to change the scaling value.

\documentclass{article}
\usepackage{amsmath}
\usepackage{amssymb}

\makeatletter
\def\fdsy@scale{1}
\newcommand\fdsy@mweight@normal{Book}
\newcommand\fdsy@mweight@small{Book}
\newcommand\fdsy@bweight@normal{Medium}
\newcommand\fdsy@bweight@small{Medium}
\DeclareFontFamily{U}{FdSymbolC}{}
\DeclareFontShape{U}{FdSymbolC}{m}{n}{
    <-7.1> s * [\fdsy@scale] FdSymbolC-\fdsy@mweight@small
    <7.1-> s * [\fdsy@scale] FdSymbolC-\fdsy@mweight@normal
}{}
\DeclareFontShape{U}{FdSymbolC}{b}{n}{
    <-7.1> s * [\fdsy@scale] FdSymbolC-\fdsy@bweight@small
    <7.1-> s * [\fdsy@scale] FdSymbolC-\fdsy@bweight@normal
}{}
\makeatother

\DeclareSymbolFont{fdarrows}{U}{FdSymbolC}{m}{n}
\SetSymbolFont{fdarrows}{bold}{U}{FdSymbolC}{m}{n}

\DeclareMathSymbol{\leftrightarrow}{\mathrel}{fdarrows}{16}
\let\updownarrow\relax
\DeclareMathSymbol{\updownarrow}{\mathrel}{fdarrows}{17}
\DeclareMathSymbol{\neswarrow}{\mathrel}{fdarrows}{18}
\DeclareMathSymbol{\nwsearrow}{\mathrel}{fdarrows}{19}

\begin{document}

$\leftrightarrow\updownarrow\neswarrow\nwsearrow$

\end{document}