# tabular: Missing number, treated as zero

The following piece of code works and compiled, when I change the \pagestyle{empty} to \pagestyle{plain} in the following style file for resume.

https://www.math.nyu.edu/student_resources/res.cls

\documentclass[overlapped, 12pt]{res}
\usepackage{enumitem}
\setlist{itemsep=0pt,leftmargin=*}

\reversemarginpar
\setlength{\textwidth}{6.in}
\newlength{\rcollength}\setlength{\rcollength}{2.in}%
\usepackage[hmargin=1.0in, bottom=0.5in, top=0.5in]{geometry}
\errorcontextlines 10000
\begin{document}

\begin{resume}
\moveleft\hoffset\vbox{\hrule width\resumewidth height 1pt}\smallskip

\section{EDUCATION}
\begin{tabular}[t] {@{} p{\textwidth}p{\rcollength} lcr}
PhD in Physics, Syracuse University, Syracuse, NY, USA & 2006-2009\\
{\sl Title} & \\\\
\end{tabular}

\end{resume}
\end{document}


However, as soon as I try to adjust the width of first column

\begin{tabular}[t] {@{} p{\textwidth-\rcollength}p{\rcollength} lcr}


I get a compilation error:

./cv_sadia.tex:53: Missing number, treated as zero.
\relax
\@startpbox ...vtop \bgroup \setlength \hsize {#1}
\@arrayparboxrestore
<template> ...startpbox {\textwidth -\rcollength }
\ignorespaces
P
l.53 P
hD in Physics, Syracuse University, Syracuse, NY, USA & 2006-2009\\


If I keep the pagestyle empty, then there is no error. Any help is appreciated, as I do want to keep page number displayed on each page.

 p{\dimexpr\textwidth-\rcollength}

• only with package calc you can have expressions of lengths. But res.cls doesn't load package calc. However, using macro \dimexpr is the better choice. – user2478 Dec 31 '15 at 17:22