\doc{Functional operators}
\ref{functional-operators}

LP allows users to \clink{declare} symbols for use in ordinary functional
notations in \dlink{term}{terms}.  A \def{function identifier}, or
\slink{operator}{functionId}, is just a simple identifier, that is, a
\slink{../symbols/symbols}{simpleId}.  It can be used as a
\dlink{constant}{constant} (e.g., \f{0}) or as an \dlink{operator}{operator}
that takes a parenthesized list of arguments (e.g., \fq{gcd(x, y)}).
