FlexMatrix{T}(rows,cols) creates a new FlexMatrix with rows indexed by rows, columns indexed by cols and all zero entries of type T (which is Number if omitted).

FlexMatrix(v::FlexVector) converts v into a one-column FlexMatrix whose sole column index is Int(1)


FlexVector{T}(idx) creates a new FlexVector with entries indexed by idx filled with zeros of type T (which defaults to Number)


FlexOnes(T,dom) creates an all 1s vector indexed by dom. If T is missing, values default to Float64.