int QSadd_col (QSprob p, int cnt, int *cmatind, double *cmatval,
    double obj, double lower, double upper, const char *name)

The QSadd_col function provides a simpler interface than QSadd_cols for adding a single variable to an existing LP, for example, the argument obj is a double rather than an array of doubles (of length 1 when adding only a single variable).

When specifying cmatval, obj, lower, and upper, it is important not to give any value larger in magnitude than QS_MAXDOUBLE (1e30). This restriction is due to the internal structures used in the QSopt solvers.

Note that when adding many variables, it is more efficient to use QSadd_cols rather than repeated calls to QSadd_col, due to the internal data management in the QSopt library.

/* Assume p is initialized to the problem in the QSload_prob example. */
/* Add a variable w, with an objective coefficient of 1.1, with a 2.1 */
/* in the first constraint, with a 3.0 in the second constraint, and  */
/* 1.0 <= w <= 2.0.                                                   */

int rval;
const char *name = "w";
int cmatind[2] = { 0, 1 };
int cmatval[2] = { 2.1, 3.0 };

rval = QSadd_col (p, 2, cmatind, cmatval, 1.1, 1.0, 2.0, name);
if (rval) {
    fprintf (stderr, "QSadd_col failed with return code %d\n", rval);
}