/ find the present value of a payment of amt that you receive numyears out
/ assuming an interest of interest.
presval:{[interest; numyears; amt]
  :amt % ((1 + (interest % 100)) xexp numyears)
  }

/ parse the command line arguments to have two lists, one for the amounts
/ and other for the yields
processargs:{[list]
  i: list ? "_";
  amounts: "F"$list[til i];
  yields: "F"$(i+1) _ list;
  out: 0;
  i: 0;
  while[i < count amounts;
	out+: presval[yields[i]; i+1; amounts[i]];
	i+: 1;
  ];
  :out
  }

  


processargs .z.x