Let fx=x-x (where {.} denotes the fractional part of x) and X, Y are its domain and range, respectively). Then
x∈-∞,12 and Y∈12,∞
x∈-∞,-12 ∪ 0,∞ and Y∈12,∞
X∈-∞,-12 ∪ 0,∞ and Y∈0,∞
None of these
fx=x-x is defined if x≥x or x∈-∞-12∪0,∞ or Y∈0,∞.