If this multimap has zero arguments, and the range space is the space ``Reals'', this routine converts it to a scalar, using the standard basis of ``1''. Note that this conversion must be done explicitly.
MultiMap(Map& m)
If the map m is linear, or is an affine map from an affine space, and if the domain is a full space, this routine casts it into a multimap.
MultiMap(GeOb& g)
If the argument g is a vector or affine vector (or can be converted to a vector), this routine casts it to a map from the dual space of the vector to the space ``Reals'', which is then in turn cast to a multimap. Note that there is no support for casting a GeOb into a zero-argument multimap.