[R] integration

[Fred J.]

Hello

after reading few nodes from the info docs. I am not
sure  if this task can be done using R:
the density function f(x,y) = 12xy(1-y) for  
0<x<1, 0<y<1
the condition of inequality (x-y)> (1/2)
what if the limits of integration are functions of the
variable I am integrating over.
is this somthing which can be done in a simple way,
with R?
examples:
Mathimatic 5.1:
In[2]:=Integrate[12*x*y*(1-y)*Boole[x-y>1/2],{y,0,1},{x,0,1}]
Maple:
Doubleint(12*x*y*(1-y)*Heaviside(x-y-1/2),x=0..1,y=0..1);

many thanks