The \boolexpr macro evaluates boolean expressions in a purely expandable way.

\boolexpr{ A \OR B \AND C } expands to 0 if the logical expression is TRUE. A, B, C may be:

• numeric expressions such as: x=y, x<>y, x>y or x<y;
• boolean switches: \iftrue 0\else 1\fi;
• conditionals: \ifcsname whatsit\endcsname 0\else 1\fi;
• another \boolexpr: \boolexpr{ D \OR E \AND F }:

\boolexpr may be used with \ifcase:

•   \ifcase\boolexpr{ A \OR B \AND C }
    What to do if true
  \else
    What to do if false
  \fi

The \switch command (which is also expandable) has the form:

• \switch
\case{<boolean expression>} ...
\case{<boolean expression>} ...
... \otherwise ...
\endswitch