Data and decision variable identifiers

Since data and decision variable identifiers are the basic components of expressions, we will review briefly here how they are used to build expressions. If r is a tuple with a field capacity of type T, then r.capacity is an expression of type T. If a is an n-dimensional array of type T, a[e 1 ]...[e n] is an expression of type T, provided that e i is well-typed. For instance, the excerpt

int limit[routes] = ...; 
dvar int transp[r in routes] in 0..limit[r]; 

contains an expression limit[r] of type integer. Indices of arrays can be complex expressions. For instance, the excerpt

int nbFlights = ...; 
range Flight = 1..nbFlights; 
{string} Employee = ...; 
dvar int crew[Flight][Employee] in 0..1; 
constraints { 
    
    forall(e in Employee) 
       forall(i in 1..nbFlights - 2) 
          crew[i][e] + crew[i+1][e] + crew[i+2][e] >= 1; 
} 

contains an integer expression crew[i+1][e] whose first index is itself an integer expression.