calculating with reals in icarus

[jan van groningen]

Hi there,

 perhaps an easy question for you:
how can you calculate in icarus with reals?

e.g.
$num=2.5
$result=$num*2

the last line doesn't work: 
error: option is not known in this context, "type in IopAss"

Do we need to use an icarus function for operations on reals?

Thanks in advance,
Koen and Jan.