Re: modificare opzione ’11pt’

Ecco una classe minimale che produce quell’errore:
`\NeedsTeXFormat{LaTeX2e}[2005/12/01]
\ProvidesClass{prova}

\DeclareOption{10pt}{\def\@ptsize{0}}
\DeclareOption{11pt}{\def\@ptsize{1}}
\DeclareOption{12pt}{\def\@ptsize{2}}
\DeclareOption*{\PassOptionsToClass{\CurrentOption}{book}}
\ProcessOptions
\relax
\LoadClass[10pt,a4paper]{book}
\RequirePackage{geometry}
\ifcase\@ptsize\relax
\geometry{%
hmarginratio=1:1,
vmarginratio=1:1}\or
\geometry{%
hmarginratio=1:2,
vmarginratio=1:2}\or
\geometry{%
hmarginratio=1:3,
vmarginratio=1:3}\or
\fi
\endinput`

Ciao
Ivan