From: Arnaldur Gylfason <arnaldur.gylfason@decode.is>

Let's say I have to parse "(_1 + _2)*_1" and "(_1/_2)*_1". I only get these command strings at runtime so I don't know the expressions at compile time.

I don't think there's any hope of making it work this way. Ultimately you really need to use run-time expression structures if you're building expressions at run-time. This is not hard to do, however. My advice would be to use boost::variant. - James Jones Administrative Data Mgmt. Webmaster 375 Raritan Center Pkwy, Suite A Data Architect Edison, NJ 08837