Originally posted by: SystemAdmin

Hello,

I am not used with CPLEX thus in other softwares this problem never happened to me, let me see if you might know how i can do this:

I am using a objective function that uses a binary decision variable lets say Y[i][j]
My objective function (maximization) will calculate a price if there Y exists in [i][j], this is Y[i][j] * Price, but will discount a penalty if Y exists in i+1[j], this is Yi+1[j] * Penalty. In the end the function would be something like:

maximize sum (i in days, j in years) Y[i][j] * Price - Yi+1[j] * Penalty

But this brings an error: operator not available for string +int

if I use Y[i][j] * Price - Y[i][j] * Penalty (no i+1) the optimization runs smoothly.

days is defined as a string, {string} Days =...; and is associated with a excel table something like this C2:E2 (monday, tuesday, sunday). Might this be the problem, to have the index as a string and therefore not possible to calculate the i+1?
How can I implement this?

Thank you for the help.
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Originally posted by: SystemAdmin

Yes, that seems likely to be the error. OPL defines a function next() to allow you to get a successor to a set member. (Check the OPL language reference for its arguments and use.)

There is a separate forum for OPL. In the future, I suggest posting OPL questions there for faster (and better) responses.

Paul

Mathematicians are like Frenchmen: whenever you say something to them, they translate it into their own language, and at once it is something entirely different. (Goethe)
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Originally posted by: SystemAdmin

Thank you. I will look up this function and ask aroun in the OLP forum. Thanks for the advice.

Best regards,
Marco Amorim
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