program integ

   use fvn_integ

   implicit none

   real(kind=dp_kind), external :: f1,f2,g,h
   real(kind=dp_kind) :: a,b,epsabs,epsrel,abserr,res

   integer :: key,ier
   a=0.
   b=1.
   epsabs=1d-8
   epsrel=1d-8
   key=2
   call fvn_integ_1_gk(f1,a,b,epsabs,epsrel,key,res,abserr,ier)
   write(*,*) "Integration of x*x between 0 and 1 : "
   write(*,*) res
   call fvn_integ_2_gk(f2,a,b,g,h,epsabs,epsrel,key,res,abserr,ier)
   write(*,*) "Integration of x*y between 0 and 1 on both x and y : "
   write(*,*) res
  
  end program
  function f1(x)

  use fvn_common

   implicit none

      real(kind=dp_kind) :: x,f1

      f1=x*x
  end function
  function f2(x,y)

  use fvn_common

   implicit none

      real(kind=dp_kind) :: x,y,f2

      f2=x*y
  end function
  function g(x)

  use fvn_common

   implicit none

      real(kind=dp_kind) :: x,g

      g=0.
  end function
  function h(x)

  use fvn_common

   implicit none

      real(kind=dp_kind) :: x,h

      h=1.
  end function