
For example, to calculate my animal companions's hp, I would use:
HD: 7
Constitution: 16
Constitution Bonus: floor( ( Constitution - 10 ) / 2 )
Total HP: floor( @HD * 4.5 ) + @HD * @Constitution Bonus
Basically I would need: floor, ceil, round, max, min
I am sure in time I could think or need of other functions other than these, but for the time being, these simple things wouldn't be a problem for javascript to interpret and apply.