# Rational variable

How would one define the domain of a symbolic variable to be rational? For a real variable $a$ it would be var('a', domain='real') or var('a', domain='RR'). However, it seems that the domain can only be 'complex', 'real', 'positive' or 'integer'. Is there a reason for this and how would one get around this if one needs to define a rational variable?

Maxima can

`declare`

some variables as`rational`

or`irrational`

, but this has not (yet) be implemented in Sage.This might be a worthwhile addition for the parts of Sage that get subcontracted to Maxima. You may try to post on sage-devel...