A proper choice of macro definitions can encode semantic
information about the visual layout being used. For instance,
an author wishing to use the notation [tex2html_wrap331] to
denote the Legendre symbol could define a new command
\legendre
that produces the desired layout. In the
absence of this facility, e.g.,when using an SGML Math
DTD that does not know about Legendre symbols, the author would
be restricted to encoding [tex2html_wrap333] in terms of the
basic operators provided, in this case, the operator that
stacks its arguments. Though both encodings would produce the
desired visual layout on paper, the encoding using the
\legendre
macro has the advantage that an
application can interpret the use of the notation as meaning a
Legendre symbol.