Title on the same line as numbering with \newtheorem?

Question

Is it possible to get \newtheorem to keep the "title" on the same line as the numbering? And give the title and the body different styles?

I would like to do something like this:

\begin{theorem}[Bayes' Theorem]
Poopy Stoopy
\end{theorem}

And have it show as:

Theorem 1.1 - Bayes' Theorem
Poopy Stoopy

With "Theorem 1.1" in bold, "Bayes' Theorem" in italics, and "Poopy Stoopy" in normal

Answer 1

You can use \theoremseparator

The code :

\documentclass{report}
\usepackage[utf8]{inputenc}
\usepackage[ thmmarks, thref]{ntheorem}
\theoremstyle{plain}
\theoremseparator{.~---}
\newtheorem{thm}{Theorem}[chapter]
\begin{document}
\chapter{}
\section{Introduction}
\begin{thm}\label{testthm}
Bayes' Theorem
\end{thm}
Poopy Stoopy.
\begin{thm}\label{testthm}
Some theorem
\end{thm}
Some text.
\end{document}

Answer 2

Use an appropriately defined theorem style.

\documentclass{article}
\usepackage{amsthm}
\newtheoremstyle{guymatz}
  {\topsep}     % ABOVESPACE
  {\topsep}     % BELOWSPACE
  {\normalfont} % BODYFONT
  {0pt}         % INDENT (empty value is the same as 0pt)
  {\bfseries}   % HEADFONT
  {}            % HEADPUNCT
  {\newline} % HEADSPACE
  {\thmname{#1}\thmnumber{ #2}\thmnote{\textnormal{ -- \textit{#3}}}} % CUSTOM-HEAD-SPEC
\theoremstyle{guymatz}
\newtheorem{theorem}{Theorem}[section]
\begin{document}
\section{Basics}
\begin{theorem}[Bayes' Theorem]
Poopy stoopy.
\end{theorem}
\begin{theorem}
Poopy stoopy.
\end{theorem}
\end{document}