[R] How to calculate a double integral ...?

[Gabor Grothendieck]

cjlu <cjlu <at> mail.ncku.edu.tw> writes:

: 
: Dear R-Friends, 
: 
: How can I calculate a double integral like
: 
:   \int_a^b \int_c^y g(x, y) dx dy
: 
: where a, b, c are constants, g(x, y), e.g.,
: g(x, y) = tan(x + y).
: 
: I tried to nested integrate() and adapt(),
: but none of them working, seemingly due to the 
: limits can not be specified constants.
: 

Integrate

   g2 <- function(x, y) g(x, y) * (x > y)

over (a,b) x (a,c).