# diff2 is intended to take partial derivatves and return a function.
#
# Example: 
#
#   > f := x^2 + y^2;
#
#   > diff2(f,x,x,y);
#     (x,y) -> 2x;
#
# Note that you have to tell diff2 what the # variables are.
#
# Definition of diff2:

diff2 := (func,var,var1,var2) -> unapply(diff(func(var1,var2),var),(var1,var2)):