Editing Cref for custom environments

Question

I recently used Roelof's answer from list the cases in text and I would like to be able to use label Cref to call the different Cases.

The environment is

\newcounter{casenum}
\newenvironment{caseof}{\setcounter{casenum}{1}}{\vskip.5\baselineskip}
\newcommand{\case}[2]{\vskip.5\baselineskip\par\noindent {\bfseries Case \arabic{casenum}:} #1\\#2\addtocounter{casenum}{1}}

and the example edited is

\documentclass{article}
\begin{document}
  \newcounter{casenum}
  \newenvironment{caseof}{\setcounter{casenum}{1}}{\vskip.5\baselineskip}
  \newcommand{\case}[2]{\vskip.5\baselineskip\par\noindent {\bfseries Case \arabic{casenum}:} #1\\#2\addtocounter{casenum}{1}}
  \begin{caseof}
    \case{$x>0$}{
      In this case, $x$ is larger than $0$ \label{c:1}
    }
    \case{$x<0$}{
      In this case, $x$ is smaller than $0$ \label{c:2}
    }
    \case{$x=0$}{In this case, $x$ equals $0$\label{c:3}}
  \end{caseof}
\end{document}

How can I go about changing Cref so that I can use say

\Cref{c:1} is a good example for positive $x$

and have Latex output it as

Case (1) is a good example for positive x.

If I use \roman instead it should say

Case (i) is a good example for positive x.

etc

where, just as for normal equations, you can click on the (1)/(i) and it will direct you to that part of the document.

Many Thanks

Answer 1

If you really want bold references:

\documentclass{article}
\usepackage{hyperref}
\usepackage[nameinlink]{cleveref}

\newcounter{casenum}
\newenvironment{caseof}
  {\setcounter{casenum}{0}}
  {\par\addvspace{.5\baselineskip}}

\renewcommand*{\thecasenum}{\arabic{casenum}}

\newcommand{\case}[2]{%
  \par\addvspace{.5\baselineskip}%
  \noindent \refstepcounter{casenum}\textbf{Case \thecasenum:}~#1\\*
  #2\ifhmode\unskip\fi
}

\crefname{casenum}{\protect\textbf{case}}{\protect\textbf{cases}}
\Crefname{casenum}{\protect\textbf{Case}}{\protect\textbf{Cases}}
\creflabelformat{casenum}{#2\textbf{(#1)}#3}

\begin{document}

  \begin{caseof}
    \case{$x>0$\label{c:1}}{%
      In this case, $x$ is larger than $0$.%
    }
    \case{$x<0$\label{c:2}}{%
      In this case, $x$ is smaller than $0$.%
    }
    \case{$x=0$\label{c:3}}{%
      In this case, $x$ equals $0$.%
    }
  \end{caseof}

  \Cref{c:1} is a good example for positive $x$.

\end{document}

Note that I used \\* to prevent a page break, and you might want to reimplement your caseof environment with enumitem (which would be another question).

If you don't want bold references, replace:

\crefname{casenum}{\protect\textbf{case}}{\protect\textbf{cases}}
\Crefname{casenum}{\protect\textbf{Case}}{\protect\textbf{Cases}}
\creflabelformat{casenum}{#2\textbf{(#1)}#3}

with:

\crefname{casenum}{case}{cases}
\creflabelformat{casenum}{#2(#1)#3}

For roman numbering, replace:

\renewcommand*{\thecasenum}{\arabic{casenum}}

with:

\renewcommand*{\thecasenum}{\roman{casenum}}

Answer 2

You could also use the enumitem package, as follows.

\documentclass{memoir}
\usepackage{hyperref}
\usepackage[nameinlink]{cleveref}

\usepackage{enumitem}

\newlist{romcases}{enumerate}{3}
\setlist[romcases,1]{%
    label=\sffamily{Case (\roman*):},
    ref=\normalfont{(\roman*)},
    wide, labelindent=0pt,itemsep=0pt,topsep=0pt
}
\crefname{romcasesi}{Case}{Cases}
\Crefname{romcasesi}{Case}{Cases}

\begin{document}

\begin{romcases}

  \item $x>0$\label{c:1}\\
    In this case, $x$ is larger than $0$.

  \item $x<0$\label{c:2}\\
    In this case, $x$ is smaller than $0$.

  \item $x=0$\label{c:3}\\
    In this case, $x$ equals $0$.

\end{romcases}

\Cref{c:1} is a good example for positive $x$.

\end{document}