Help: Switch constraints on or off

Hi there,



I am wondering how I can use an if statement to turn a constraint on or off.

For example in my problem I have the following constraint:



subject to linctr14 {i in PeriodsCount: i == 1}: StorageEnergy[i] = (StorageStateCharge * StorageEnergyRating + ((StorageEfficiencyCharge * (StoragePowerCharge[i])) - ((StoragePowerDischarge[i]) / StorageEfficiencyDischarge)));



Now, I only want to consider storage in my problem if an object storage actually exists.

For that, I would have a StorageStatusFlag which if equal to "1" then I would consider the constraint in my problem.

For example: 



If (StorageStatusFlag == 1) then

    subject to linctr14 {i in PeriodsCount: i == 1}: StorageEnergy[i] = (StorageStateCharge * StorageEnergyRating + ((StorageEfficiencyCharge * (StoragePowerCharge[i])) - ((StoragePowerDischarge[i]) / StorageEfficiencyDischarge)));

end if


This is what I used to do in "mosel" language from FICO Xpress (I don't have a license anymore so I am discovering GLPK ). How can I do this in GLPK language? What's the workaround that we can use for this?



Many thanks in advance for your help. It's really appreciated.



Kind regards,

Manuel.