or download this
>perl rat.pl 0.49420098210293
0: 0 / 1 = 0 (-0.5)
...
1: 390093397190 / 789341606587 = 0.49420098210293 (1e-025)
13: 5447778312567 / 11023406488157 = 0.49420098210293 (-9e-028)
9: 49420098210293 / 100000000000000 = 0.49420098210293 (0)