getMapped: function [a,b,i][
    round .to:1 b\0 + ((i - a\0) * (b\1 - b\0))/(a\1 - a\0)
]

rangeA: @[0.0 10.0]
rangeB: @[0-1.0 0.0]

loop 0..10 'x [
    mapped: getMapped rangeA rangeB to :floating x
    print [x "maps to" mapped]
]