Originally posted by: arguen

I am trying to unify the following two sets:

{string
} NP_v[v in V] = 
{p| <v, p, d, t> in Arc_ijvt, v in V
}; 
// Set of pick-up ports for vessel v 
{string
} ND_v[v in V] = 
{d| <v, p, d, t> in Arc_ijvt, v in V
}; 
// Set of delivery ports for vessel v

with the following code:

NPD_v[v in V]= NP_v[v in V] union ND_v[v in V]; 
// Set of ports for vessel v

But it is giving "Cannot use type boolean for string" error.

by the way "V" is also a string set with the names of vessels.
Any help would be appreciated.
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Originally posted by: GGR

Hi

I would say there is several mistake in your code.

First you could simplify the definition of your 2 sets by telling

{string
} NP_v[v in V] = 
{p| <v, p, d, t> in Arc_ijvt
} 
{string
} ND_v[v in V] = 
{d| <v, p, d, t> in Arc_ijvt
}

Second OPL is right. In your second expression v in V is a boolean expression, not a string

You have to write

{string
} NPD_v[v in V]= NP_v[v] union ND_v[v];

Hope that helps
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#OPLusingCPOptimizer

Originally posted by: arguen

Thank you for your answer and recommendations.
It helped.
#DecisionOptimization
#OPLusingCPOptimizer