Sections, subsections numbering

Question

I want to have the following sections numbering style:

I. Section

A. Subsection

1. SubSubsection

The following lines of code present different style:

\renewcommand{\thesection}{\Roman{section}} 

\renewcommand{\thesubsection}{\thesection.\Alph{subsection}}

\renewcommand\thesubsubsection{\thesubsection.\arabic{subsubsection}}

I. Section

I.A. Subsection

I.A.1. SubSubsection

Your help is highly appreciated!

Best regards,

Answer 1

The following does almost what you want, except for the font sizes:

\documentclass[]{article}
    \makeatletter %needed
    % reduce space between number and section title a bit
    \renewcommand{\@seccntformat}[1]%
        {{\csname the#1\endcsname\hspace{.25em}}}
    % allow more space in ToC for section number (4.5em here)
    \renewcommand{\l@section}{\@dottedtocline{1}{1.5em}{4.5em}}
    % adjust indentation for the lower levels
    \renewcommand{\l@subsection}{\@dottedtocline{1}{3.0em}{1.5em}}
    \renewcommand{\l@subsubsection}{\@dottedtocline{1}{3.5em}{2.5em}}
\makeatother

\renewcommand{\thesection}{\Roman{section}.}    
\renewcommand{\thesubsection}{\Alph{subsection}.}    
\renewcommand\thesubsubsection{\protect\phantom{\thesubsection}%
    \arabic{subsubsection}.}    

\begin{document}
\tableofcontents

\section{A section}

\subsection{A subsection}

\subsubsection{A subsubsection}

\end{document}

Note the \protect in the redefinition of \thesubsubsection: the argument of the macro is a moving argument (used in several places, here in the headers and in the ToC), so certain macros (like \phantom) need a \protect to avoid compilation errors.

EDIT: Added some extra redefinitions to give space for the longer Roman numerals.

Answer 2

Incorporating the space inside of the \thesubsubsection is a bad idea since this space will enter the cross-referencing as well, so \ref{foo} would give ______1, where ______ indicates the additional space.

I suggest to change the \@seccntformat macro for subsubsection, using \ifnum0=\pdfstrcmp in order to check whether the counter is subsubsection etc.

\documentclass{article}

\usepackage{tocloft}


\renewcommand*{\thesection}{\Roman{section}.}
\renewcommand*{\thesubsection}{\Alph{subsection}.}
\renewcommand*{\thesubsubsection}{\arabic{subsubsection}.}
\newlength{\subsubsectionnumberindent}
\setlength{\subsubsectionnumberindent}{3ex}

\addtolength{\cftsubsubsecnumwidth}{-3.5ex}


\newcommand{\subsubsectionheadingformat}{%
  \hskip\subsubsectionnumberindent\arabic{subsubsection}.\quad%
}

\makeatletter
\let\latex@@seccntformat\@seccntformat
\renewcommand{\@seccntformat}[1]{%
  \ifnum0=\pdfstrcmp{#1}{subsubsection}%
  \subsubsectionheadingformat%
  \else
  \latex@@seccntformat{#1}%
  \fi
}
\makeatother
\begin{document}

\tableofcontents


Please see \fbox{\ref{foosubsubsec}}

\section{Section}
\subsection{Subsection}
\subsubsection{SubSubsection} \label{foosubsubsec}

\end{document}