ceiling(RWeilDivisor) -- produce a WeilDivisor whose coefficients are ceilings or floors of the divisor

Description

Start with a rational or real Weil divisor. We form a new divisor whose coefficients are obtained by applying the ceiling or floor function to them.

 i1 : R = QQ[x, y, z] / ideal(x *y - z^2); i2 : D = divisor({1/2, 4/3}, {ideal(x, z), ideal(y, z)}, CoefficientType => QQ) o2 = 4/3*Div(y, z) + 1/2*Div(x, z) o2 : QWeilDivisor on R i3 : ceiling( D ) o3 = 2*Div(y, z) + Div(x, z) o3 : WeilDivisor on R i4 : floor( D ) o4 = Div(y, z) o4 : WeilDivisor on R i5 : E = divisor({0.3, -0.7}, {ideal(x, z), ideal(y,z)}, CoefficientType => RR) o5 = -.7*Div(y, z) + .3*Div(x, z) o5 : RWeilDivisor on R i6 : ceiling( E ) o6 = Div(x, z) o6 : WeilDivisor on R i7 : floor( E ) o7 = -Div(z, y) o7 : WeilDivisor on R