allow adjacent prefix/postfix operators of the same precedence #18
Description
The documentation for mparser's expression parser says
Adjacent prefix and postfix operators of the same precedence are not well-formed. For example, if (-) denotes prefix negation, --x is not a well-formed expression (if (--) does not denote an operator on its own).
This limitation is inconvenient. As a feature request, it would be nice to remove this limitation, so that e.g. - - x would mean - (- x) for a prefix operator -.