Originally posted by: LindaKing

Hi,everybody!

I define a dvar boolean x. And in one dexpr I need to express multiplying x with a float variable. As follows:

...

float x;

...

dvar boolean y[s][s];

...

dexpr float z = x*y[s][s];

But there is an error" Operator not available for dvar boolean[][s] * float".

I knew there is an example in tutorial which is

dvar 
boolean weightInKnapsack1; // Is the object1 in the knapsack ?
dvar 
boolean weightInKnapsack2;
dvar 
boolean weightInKnapsack3;

int maxWeight=10; // The total weight should be less than maxWeight

int weight1=3;
int weight2=9;
int weight3=2;

// Let us try to take as many objects as we can
maximize (weightInKnapsack1+weightInKnapsack2+weightInKnapsack3);

subject to
{
   
   weightInKnapsack1*weight1+
   weightInKnapsack2*weight2+
   weightInKnapsack3*weight3<=maxWeight;
}

________________________________________________

Can dvar boolean be multiplied with float type?

You need an index on the dexpr as well. Like so:

range S = 0..1;
float x = 0.5;
dvar boolean y[S][S];
dexpr float z[s1 in S][s2 in S] = x * y[s1][s2];

Originally posted by: LindaKing

Thank you very much. This does help.

I found that I made a mistake when I indicate the range. 

But I have another question.

......

int nPoint = ...;
range Point = 0..(nPoint-1);
int nSlice = ...;
range Division = 0..(nDivision-1);

//Decision Variables

dvar int+ Start[Division] in Point;
dvar boolean After[Point][Start];   

......

Here I want to indicate the relationship between sampling points and the division of one day.

For example, nPoint=48 sampling points (24hr, every 30min one sample).

The Division is defined by the starting point and other points included in this division. I use "dvar boolean After" to show whether a point is after the starting point of certain division or not.

But the Start is also a dvar. Is the definition shown above illegal?

You cannot use a decision variable (Start) as an index. I am not exactly clear how that After[] array should look like. Do you want something like this:

dvar boolean After[Point][Division];
subject to {
// After[p][d] is 0 if it is before the Start[d]
forall (p in Point)
   forall (d in Division)
      (p <= Start[d] - 1) => (After[p][d] == 0);
// After[p][d] is 1 if it is after Start[d]
forall (p in Point)
   forall (d in Division)
      (p >= Start[d]) => (After[p][d] == 1);
}

Originally posted by: LindaKing

OK. I will try to solve it as you suggest. Thank you very much.