Reference algorithmic line numbers using cleveref

Question

consider the following example:

\documentclass[a4paper,final]{report}

\usepackage{cleveref}
\usepackage{algorithmic}

\Crefname{ALC@unique}{Line}{Lines}

\begin{document}

Tests: 

\begin{algorithmic}[1]
\REQUIRE $x$ and $y$
\ENSURE $|x + y|$
\STATE $z = x + y$
\IF{$z<0$}
\RETURN $-z$\label{l1}
\ELSE
\RETURN $z$
\ENDIF
\end{algorithmic}

cref\{l1\}: \cref{l1}, ref\{l1\}: \ref{l1}

\begin{algorithmic}[1]
\REQUIRE $x$ and $y$
\ENSURE $|x - y|$
\STATE $z = x - y$
\IF{$z<0$}
\RETURN $-z$\label{l2}
\ELSE
\RETURN $z$
\ENDIF
\end{algorithmic}

cref\{l2\}: \cref{l2}, ref\{l2\}: \ref{l2}

\end{document}

This will output (apart from the pseudocode):

cref{l1}: line 3, ref{l1} 3

cref{l2}: line 9, ref{l2} 3

As you will notice, \cref{l2} returns an incorrect line number. Any suggestions on how to fix this?

Answer 1

cleveref only claims to support a limited number of packages and algorithmic is not on that list. However, adding \setcounter{ALC@unique}{0} after the beginning of your algorithmic enviroments fixes the problem, i.e., writing

\begin{algorithmic}[1]
\setcounter{ALC@unique}{0}
\REQUIRE $x$ and $y$

etc.

I suggest you wrap this up in a new environment, so that you do not have to write it each time.

If you also want hyperref to behave properly, then I suggest packaging as follows

\documentclass[a4paper,final]{report}

\usepackage{algorithmic}
\usepackage{hyperref}
\usepackage{cleveref}

\Crefname{ALC@unique}{Line}{Lines}
\newcounter{myalg}
\AtBeginEnvironment{algorithmic}{\refstepcounter{myalg}}
\makeatletter
\@addtoreset{ALC@unique}{myalg}
\makeatother

\begin{document}

Test 1

\begin{algorithmic}[1]
\REQUIRE $x$ and $y$
\ENSURE $|x + y|$
\STATE $z = x + y$
\IF{$z<0$}
\RETURN $-z$\label{l1}
\ELSE
\RETURN $z$
\ENDIF
\end{algorithmic}

cref\{l1\}: \cref{l1}, ref\{l1\}: \ref{l1}

\vfill

Test 2

\begin{algorithmic}[1]
\REQUIRE $x$ and $y$
\ENSURE $|x - y|$
\STATE $z = x - y$
\IF{$z<0$}
\RETURN $-z$\label{l2}
\ELSE
\RETURN $z$
\ENDIF
\end{algorithmic}

cref\{l2\}: \cref{l2}, ref\{l2\}: \ref{l2}

\end{document}