It would be useful to be able of provide extra properties to the expressions, that allow `Cadabra`

, `SymPy`

or `Mathematica`

to improve their simplification algorithms.

An existing example is the property `Integer`

. It could be useful to include others like `Real`

, `Positive`

, `Negative`

, or even a sort of `In([<list of values>])`

## Question

Is any of these properties currently defined?