function _integral_rec(v, sum=0, i=0, arr=[]) = (i == len(v)) ? arr :
  let(
    nsum = sum + v[i]
  )
  _integral_rec(v, nsum, i+1, [each arr, nsum]);
integral = function (v, initial=0) _integral_rec(v, initial);

echo(integral([[5,6],[2,3],[4,5],[7,1]], [0,0]));