6

The title says it all, I am using the package kpfonts and I would like to declare a math operator that has a widearc on top. However, when I compile I don't get any arc.

\documentclass{article}

\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage{
  kpfonts
}

\DeclareMathOperator{\dSing}{\widearcarrow{Sing}}
\DeclareMathOperator{\sSing}{\widehat{Sing}}
\begin{document}    
\[\dSing(X) \quad \widearcarrow{Sing}\quad\sSing(A)\]
\end{document}

enter image description here

Notice that the command widehat is working.

Thanks for your help!

2
  • 1
    Welcome to TeX.SE.
    – Mico
    Commented Aug 11, 2019 at 18:49
  • Thanks @Mico and thanks everybody for your answers! Commented Aug 12, 2019 at 9:23

3 Answers 3

7

Apparently, math accents from family 3 don't work in \operatorname.

You can use a lower level interface:

\documentclass{article}

\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage{kpfonts}

\DeclareRobustCommand{\dSing}{%
  \mathop{\widearcarrow{\mathrm{Sing}}}\nolimits
}
\DeclareMathOperator{\sSing}{\widehat{Sing}}

\begin{document}

\[
\dSing(X) \quad \widearcarrow{Sing} \quad \sSing(A)
\]

\end{document}

enter image description here

7

Replace \newcommand instead of \DeclareMathOperator and your code works perfectly.

For the differences between \newcommandand \DeclareMathOperator I suggest to see this link: newcommand vs. DeclareMathOperator

enter image description here

\documentclass{article}
\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage{kpfonts}
\newcommand{\dSing}{\widearcarrow{\mathrm{Sing}}}
\newcommand{\sSing}{\widehat{\mathrm{Sing}}}
\begin{document}    
\[\dSing(X) \quad \widearcarrow{Sing}\quad\sSing(A)\]
\end{document}
2
  • 3
    Good answer! One tweak: if you redefine the operator font or \mathrm, so that they’re no longer the same, you can replace \mathrm{Sing} with \operatorname{Sing}.
    – Davislor
    Commented Aug 12, 2019 at 3:57
  • @Davislor I thank you and all of you from the bottom of my heart. I've only had luck :-)
    – Sebastiano
    Commented Aug 12, 2019 at 6:53
4
\renewcommand{\d}[1]{\widearcarrow{\text{#1}}}
\def\dSing{\d{Sing}}

Don't know why it works this way, but it does. May be a feature of the definition of widearcarrow in the package.

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