\ProvidesPackage{dsfont}
  [1995/08/01 v0.1 Double stroke roman fonts]

\def\ds@whichfont{dsrom}
\DeclareOption{sans}{\def\ds@whichfont{dsss}}
\ProcessOptions\relax

\DeclareMathAlphabet{\mathds}{U}{\ds@whichfont}{m}{n}
\endinput