autoref on newtheorem

Question

I want to be able to print the names of my own theorems with autoref. E.g. on

\begin{lemma}
\label{lemma_foo}
  Some lemma
\end{lemma}

\autoref{lemma_foo}

I want something like "Lemma 3.2" being printed.

My current approach is:

\newtheorem{lemma}{Lemma}[chapter]
\newcommand{\lemmaautorefname}{Lemma}

\newtheorem{definition}[lemma]{Definition}
\newcommand{\definitionautorefname}{Definition}

Definition shares the counter with lemma, which is intended, however it has the side effect, that referencing definitions results in them being called lemmas.

How do I fix this?

Answer 1

As long as the lemma and definition environments are defined after the hyperref and cleveref packages are loaded, using \cref in lieu of \autoref should give you what you want.

\documentclass{report} % or 'book'?
\usepackage{ntheorem}  % or 'amsthm'?
\usepackage[colorlinks]{hyperref}
\usepackage[capitalize,nameinlink,noabbrev]{cleveref} % to emulate \autoref style

\newtheorem{lemma}{Lemma}[chapter]
\newcommand{\lemmaautorefname}{Lemma}
\newtheorem{definition}[lemma]{Definition}
\newcommand{\definitionautorefname}{Definition}

\setcounter{chapter}{1} % just for this example

\begin{document}
\begin{lemma}
\label{lemma_foo}
  Some lemma
\end{lemma}
\autoref{lemma_foo}  (correct) and \cref{lemma_foo} (correct) \dots

\begin{definition}
\label{definition_bar}
  A definition
\end{definition}
\autoref{definition_bar} (incorrect) and \cref{definition_bar} (correct) \dots

\end{document}

Answer 2

I managed to get this to work with \autoref, but it will only allow the counters to count for each type. So you would have Definition 1.1 then Definition 1.2 and if you add a lemma after that Lemma 1.1. It might be acceptable.

\newtheorem{lemma}{Lemma}[section]
\newtheorem{definition}{Definition}[section]

\newcommand{\lemmaautorefname}{Lemma}
\newcommand{\definitionautorefname}{Definition}