Doubt

no, you shouldn’t do that

the correct representation is

x = [x] + {x}

where [x] is an integer and {x} lies in [0,1)

if you take something like x + 0.1y, it doesn’t guarantee that the fractional part stays between 0 and 1, which breaks the definition

so always use

x = n + f

where n is integer and 0 ≤ f < 1, that’s the standard and safe way