Ch4, Ex7

declare DGenerate DSum
fun {DGenerate N}
   fun {$}
      N|{DGenerate N+1}
   end
end

fun {DSum F A Limit}
   if Limit>0 then
      X|Xr={F}
   in
      {DSum Xr A+X Limit-1}
   else A end
end
local S in
   S={DSum {DGenerate 0} 0 15}
   {Browse S}
end