[Tex/LaTex] How to put a line number with levels in algorithm

algorithmsline-numbering

\documentclass[a4paper, 10pt, 3p, final, twocolumn, times]{elsarticle}
\usepackage{algorithm}
\usepackage{algorithmic}
\begin{document}
\begin{algorithm}[htbp]
    \caption{somealg}
    \label{alg}
    \begin{algorithmic}[1]
    \REQUIRE input
    \ENSURE output
    \STATE statement 1
    \FOR {i = 1 to $l$}
    \STATE statement in loop 1
    \STATE statement in loop
    \ENDFOR
    \end{algorithmic}
    \end{algorithm}
\end{document}

I want to add line number in my algorithm and the line number of the statement inside the "for" loop should be 2.1 instead of 3. How should I do? Thank you.

Best Answer

The following does not allow for nesting of loop structures within each other, but provides the sub-numbering of a pseudo-code grouping (like \FOR, \WHILE, \LOOP and \REPEAT):

enter image description here

\documentclass{article}

\usepackage{algorithm,algorithmic,xpatch}

\makeatletter
\xpatchcmd{\algorithmic}% <cmd>
  {\arabic{ALC@line}}% <search>
  {\theALC@line}% <replace>
  {}{}% <success><failure>
\xpatchcmd{\algorithmic}{1.2em}{1.5em}{}{}% Increase label width

\newcommand{\updatelinenoprint}{%
  \setcounter{parentcounter}{\value{ALC@line}}% Store current line number
  \setcounter{ALC@line}{0}% Restart line counter
  \renewcommand{\theALC@line}{\theparentcounter.\arabic{ALC@line}}% Update printing mechanism
}
\newcommand{\revertlinenoprint}{%
  \setcounter{ALC@line}{\value{parentcounter}}% Restore original line number
}%

\renewcommand{\theALC@line}{\arabic{ALC@line}}
\newcounter{parentcounter}
\xapptocmd{\algorithmic}{%
  \xapptocmd{\ALC@for}{\updatelinenoprint}{}{}\xpretocmd{\endALC@for}{\revertlinenoprint}{}{}%
  \xapptocmd{\ALC@whl}{\updatelinenoprint}{}{}\xpretocmd{\endALC@whl}{\revertlinenoprint}{}{}%
  \xapptocmd{\ALC@loop}{\updatelinenoprint}{}{}\xpretocmd{\endALC@loop}{\revertlinenoprint}{}{}%
  \xapptocmd{\ALC@rpt}{\updatelinenoprint}{}{}\xpretocmd{\endALC@rpt}{\revertlinenoprint}{}{}%
}
\makeatother

\begin{document}

\begin{algorithm}[htbp]
  \caption{somealg}
  \begin{algorithmic}[1]
    \REQUIRE input
    \ENSURE output
    \STATE statement 1
    \FOR {$i = 1$ to $l$}
      \STATE statement in loop 1
      \STATE statement in loop
    \ENDFOR
    \STATE statement 2
    \WHILE {$i < 10$}
      \STATE statement in loop 1
      \STATE statement in loop
    \ENDWHILE
  \end{algorithmic}
\end{algorithm}

\end{document}
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