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# GRBVar

class GRBVar

  Gurobi variable object. Variables are always associated with a particular model. You create a variable object by adding a variable to a model (using `GRBModel::addVar`), rather than by using a `GRBVar` constructor.

  The methods on variable objects are used to get and set variable attributes. For example, solution information can be queried by calling `get` ( `GRB_DoubleAttr_X`). Note that you can also query attributes for a set of variables at once. This is done using the attribute query method on the `GRBModel` object (`GRBModel::get`).

  The full list of attributes can be found in the Attributes section of this document. Examples of how to query and set attributes can also be found in this section.

  char get(GRB_CharAttr attr)
  double get(GRB_DoubleAttr attr)
  int get(GRB_IntAttr attr)
  string get(GRB_StringAttr attr)

    Query the value of an attribute.

    Parameters:

      attr – The attribute being queried.

    Returns:

      The current value of the requested attribute.

  int index()

    This method returns the current index, or order, of the variable in the underlying constraint matrix.

    Note that the index of a variable may change after subsequent model modifications.

    Returns:

      -2: removed, -1: not in model, otherwise: index of the variable in the model

  bool sameAs(GRBVar var2)

    Check whether two variable objects refer to the same variable.

    Parameters:

      var2 – The other variable.

    Returns:

      Boolean result indicates whether the two variable objects refer to the same model variable.

  void set(GRB_CharAttr attr, char newvalue)
  void set(GRB_DoubleAttr attr, double newvalue)
  void set(GRB_IntAttr attr, int newvalue)
  void set(GRB_StringAttr attr, const string &newvalue)

    Set the value of an attribute.

    Parameters:

      - attr – The attribute being modified.

      - newvalue – The desired new value of the attribute.

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