The function CollapseNested collapses a nested integral into a multiple integral given as a single Int or int function call.

If v is an expression of nested definite and indefinite integrals, only the matching integrals will be collapsed.

You can control whether options present in the integral v will appear in the output. If the option stripoptions is given, none of the options in the integral v will appear in the output.  If the option intersectoptions is given, the options that appear in every integral will appear in the output. Otherwise, all options on any of the integrals will appear in the output.

If the option matchtypes is given, only integrals of the same type will be collapsed.  For example, two nested Int integrals will be collapsed, but nested int and Int integrals will not be collapsed.

If the option norecurse if given, only the outermost integrals will be collapsed.

Int(f(x,y),[x, y]) = Int(Int(f(x,y),x),y)

Int(f(x,y),[x, y])

Int(int(f(x,y),x),y)

Int(Int(f(x,y),[x = a .. b, y = c .. d]),[x, y])

Int(Int(Int(f(x,y),x = a .. b),y = c .. d),[x, y])