Function SCIPaddVarToRow 

pub unsafe extern "C" fn SCIPaddVarToRow(
    scip: *mut SCIP,
    row: *mut SCIP_ROW,
    var: *mut SCIP_VAR,
    val: f64,
) -> SCIP_RETCODE

resolves variable to columns and adds them with the coefficient to the row

@return \ref SCIP_OKAY is returned if everything worked. Otherwise a suitable error code is passed. See \ref SCIP_Retcode “SCIP_RETCODE” for a complete list of error codes.

@attention If the absolute value of val is below the SCIP epsilon tolerance, the variable will not added.

@pre this method can be called in one of the following stages of the SCIP solving process: - \ref SCIP_STAGE_SOLVING

@note In case calling this method in the enforcement process of an lp solution, it might be that some variables, that were not yet in the LP (e.g. dynamic columns) will change their lp solution value returned by SCIP. For example, a variable, which has a negative objective value, that has no column in the lp yet, is in the lp solution on its upper bound (variables with status SCIP_VARSTATUS_LOOSE are in an lp solution on it’s best bound), but creating the column, changes the solution value (variable than has status SCIP_VARSTATUS_COLUMN, and the initialization sets the lp solution value) to 0.0. (This leads to the conclusion that, if a constraint was violated, the linear relaxation might not be violated anymore.)

@note When several variables are added to a row with the use of this function, performance can be improved by calling SCIPcacheRowExtensions() before these additions and SCIPflushRowExtensions() after.