numerator -- numerator of a fraction

i1 : numerator (4/6)

o1 = 2

i2 : R = frac(ZZ[x,y]);

i3 : numerator((x+2*y-3)/(x-y))

o3 = x + 2y - 3

o3 : ZZ [x, y]

i4 : R = QQ[a..d]/(a^2,b^2,c^3);

i5 : hf = hilbertSeries R

           2    3    4     5    7
     1 - 2T  - T  + T  + 2T  - T
o5 = ----------------------------
                      4
               (1 - T)

o5 : Expression of class Divide

i6 : numerator hf

           2    3    4     5    7
o6 = 1 - 2T  - T  + T  + 2T  - T

o6 : ZZ [T, MonomialOrder => RevLex, Inverses => true]