Floating point numbers (the Num type) are written in the standard 'e' scientific notation:
2e2 # same as 200e0, 2e2, 200.0e0 and 2.0e26.02e23-2e481e-91e0
A number like 3.1416 is specifically not floating point, but rational (the Rat type), equivalent to 3927/1250. On the other hand, Num(3.1416) would be considered a floating literal though by virtue of mandatory constant folding.