Set the type of the variable. Binary or floating point.

unsigned char set_binary(lprec *lp, int column, unsigned char must_be_bin);

Return Value

set_binary returns TRUE (1) if the operation was successful. A return value of FALSE (0) indicates an error.



Pointer to previously created lp model. See return value of make_lp, read_lp, read_LP, read_mps, read_freemps, read_MPS, read_freeMPS, read_XLI


The column number of the variable that must be set. It must be between 1 and the number of columns in the lp.


TRUE (1) if the variable must be binary, FALSE (0) if not.


The set_binary function defines if a variable must be binary or not. Default a variable is not binary. A binary variable is an integer variable with a lower bound of 0 and an upper bound of 1. This function also sets these bounds. The argument must_be_bin defines what the status of the variable becomes. From the moment there is at least one integer variable in the model, the Branch and Bound algorithm is used to make these variables integer. Note that solving times can be considerably larger when there are integer variables. See integer variables for a description about integer variables.


#include <stdio.h>
#include <stdlib.h>
#include "lp_lib.h"

int main(void)
  lprec *lp;

  /* Create a new LP model */
  lp = make_lp(0, 2);
  if(lp == NULL) {
    fprintf(stderr, "Unable to create new LP model\n");

  set_binary(lp, 1, TRUE); /* sets variable 1 to binary */


lp_solve API reference

See Also make_lp, read_lp, read_LP, read_mps, read_freemps, read_MPS, read_freeMPS, read_XLI, is_binary, is_int, set_int