int sym_set_continuous(sym_environment *env, int index)
This routine is used to set the type of a variable to be integer.
| sym_environment *env | INOUT | Pointer to the SYMPHONY environment. | 
| int index | IN | The index of the variable to be modified. Note that, it has to be at most the number of columns. | 
| FUNCTION_TERMINATED_NORMALLY | Function invoked successfully. | 
| FUNCTION_TERMINATED_ABNORMALLY | Function invoked unsuccessfully. |