在「;」周圍的AMPL語法錯誤

Question

新來AMPL，得到一個語法錯誤在以下模型選址「>>>>>; < < < < < <」作爲問題：

set Types; 
param demand {Types}; 
set Machines; 
param prod_cost {Machines, Types}; 
param days_reqd {Machines, Types}; 
param days_avail {Machines}; 

var x {Machines, Types} >=0; # amount produced 

minimize total_cost: sum {m in Machines, t in Types} prod_cost[m,t] * x[m,t] ; 

subject to machine_capacity: sum {m in Machines, t in Types} x[m,t] * days_reqd[m,t] <= days_avail[m] ; 

subject to satisfy_demand: sum {m in Machines, t in Types} x[m,t] >= demand ; 

Answer 1

的demand參數被索引超過設定Types，因此需要下標，例如

subject to satisfy_demand{t in Types}: 
    sum {m in Machines} x[m,t] >= demand[t] ;