Print number of previous page

Question

I know that I can use \thepage to get the number of the current page. However I'd like to print out the page-number of the previous page. How can I go about that?

Background:
I don't number the first page in my document and want to start the numbering with 1 on the second page. However I can't use \setcounter{page}{1} on that site as I want every mechanism (namely the bindingoffset of the geometry package) to treat the page-numbering as if the first page does have the number 1. In short I want the pages with a (then) even page number to be treated as odd pages and vice versa.

Answer 1

You can get the pagenumber of the previous page with the following expression: \the\numexpr\value{page}-1\relax

Answer 2

Using \thepage is not guaranteed to yield the number of the current page.

Example:

\documentclass{article}

\usepackage{lipsum} % for mock text

\setlength{\textheight}{2cm} % to make smaller pictures

\begin{document}

\lipsum*[2] \\
--\thepage-- is wrong

\end{document}

You need to use the \label-\ref mechanism to ensure correctness.

\documentclass{article}
\usepackage{refcount}

\usepackage{lipsum} % for mock text

\newcounter{printpagecount}
\newcommand{\printpage}[1]{%
  \refstepcounter{printpagecount}%
  \label{\theprintpagecount}%
  \the\numexpr\getpagerefnumber{\theprintpagecount}+(#1)\relax
}

\setlength{\textheight}{2cm} % to make smaller pictures

\begin{document}

\lipsum*[2] \\
\printpage{0} (current) and \printpage{-1} (previous)

\end{document}

If instead your aim is to confuse readers by having odd numbered pages on the left and even numbered ones on the right, just define suitably \thepage:

\documentclass[twoside,a5paper]{article}
\usepackage{geometry}

\usepackage{lipsum} % for mock text

\renewcommand{\thepage}{\the\numexpr\value{page}-1\relax}


\begin{document}

\thispagestyle{empty}

\lipsum[1-30]


\end{document}

A5 paper used just for making a smaller picture.

Answer 3

It occurred to me that the way I originally did this is a bit silly and completely unnecessary…

You can just temporarily change the value of the page counter and call \thepage. Who knows what I was thinking. It was probably late at night.

\documentclass{article}
\newcommand{\thepagelessone}{%
  \addtocounter{page}{-1}%
  \thepage
  \stepcounter{page}}
\begin{document}
\setcounter{page}{5}
\verb|\thepage|: \thepage; \verb|\thepagelessone|: \thepagelessone

\pagenumbering{roman}
\setcounter{page}{7}
\verb|\thepage|: \thepage; \verb|\thepagelessone|: \thepagelessone
\end{document}

---

Original silly solution

Here's a solution using expl3. It correctly handles the various styles of page numbering (arabic, roman, etc.)

It works by expanding \thepage once, then detokenizing the result. The current page number (\c@page) is removed from the end of the token list and replaced by this number less one.

\documentclass{article}
\usepackage{xparse}
\makeatletter
\ExplSyntaxOn
\tl_new:N \l__raven_thepage_tl
\int_new:N \l__raven_page_int
\cs_new:Nn \__raven_page_less_one:n
  {
    \tl_set:Nn \l__raven_thepage_tl { #1 }
    \tl_remove_once:Nn \l__raven_thepage_tl { \c@page }
    \int_set_eq:NN \l__raven_page_int \c@page
    \int_decr:N \l__raven_page_int
    \tl_put_right:Nn \l__raven_thepage_tl { \l__raven_page_int }
    \tl_use:N \l__raven_thepage_tl
  }
\cs_generate_variant:Nn \__raven_page_less_one:n { o }
\NewDocumentCommand \thepagelessone { }
  {
    \__raven_page_less_one:o { \thepage }
  }
\ExplSyntaxOff
\makeatother
\begin{document}
\setcounter{page}{5}
\verb|\thepage|: \thepage; \verb|\thepagelessone|: \thepagelessone

\pagenumbering{roman}
\setcounter{page}{7}
\verb|\thepage|: \thepage; \verb|\thepagelessone|: \thepagelessone
\end{document}