go =>
  items(Items),
  weights(Weights),
  values(Values),
  knapsack_max_weight(MaxWeight),

  knapsack(Weights,Values,MaxWeight, X,TotalWeight,TotalValue),
  nl,

  printf("Total weight: %0.2f Total value: %0.2f\n", TotalWeight,TotalValue),
  foreach(I in 1..Items.len)
     if X[I] > 0.0 then
       printf("%-8w: ",Items[I]),
       if X[I] == Weights[I] then
         printf("%0.2f (%w)", Weights[I], all)
       else
         printf("%-0.2f",X[I])
       end,
       nl
     end
  end,
  nl.

knapsack(Weights,Values,MaxWeight, X,TotalWeight,TotalValue) =>
  N = Weights.len,

  X = new_list(N),
  X :: 0.0..max(Weights),

  TotalWeight #= sum(X),
  TotalWeight #<= MaxWeight,
  foreach(I in 1..N)
     X[I] #<= Weights[I]
  end,

  WeightsInv = [1/Weights[I] : I in 1..N],
  TotalValue #= sum([X[I]*Values[I]*WeightsInv[I] : I in 1..N]),

  Vars = X ++ [TotalWeight],
  solve($[glpk,max(TotalValue)],Vars).

% data
knapsack_max_weight(15.0).
items([beef,pork,ham,greaves,flitch,brawn,welt,salami,sausage]).
weights([3.8,5.4,3.6,2.4,4.0,2.5,3.7,3.0,5.9]).
values([36,43,90,45,30,56,67,95,98]).