Added set_obj_integral Method (#101)

* Added set_obj_integral() function

* Added test for set_obj_integral

* Moved new method to Model<ProblemCreated>

* Update method signature to always return Self

* Updated CHANGELOG.md

CHANGELOG.md

@@ -2,6 +2,7 @@
 
 ## unreleased
 ### Added
+ - Added method `set_obj_integral` to allow specifying that the objective value is always integral.
 ### Fixed
 ### Changed
 ### Removed

src/model.rs

@@ -206,6 +206,14 @@ impl Model<ProblemCreated> {
             .set_cons_modifiable(cons, modifiable)
             .expect("Failed to set constraint modifiable");
     }
+
+    /// Informs the SCIP instance that the objective value is always integral and returns the same `Model` instance.
+    pub fn set_obj_integral(mut self) -> Self {
+        self.scip
+            .set_obj_integral()
+            .expect("Failed to set the objective value as integral");
+        self
+    }
 
     /// Adds a new variable to the model with the given lower bound, upper bound, objective coefficient, name, and type.
     ///
@@ -1068,6 +1076,23 @@ mod tests {
         assert_eq!(sol.obj_val(), model.obj_val());
     }
 
+    #[test]
+    fn set_obj_integral() {
+        let model = Model::new()
+            .hide_output()
+            .include_default_plugins()
+            .read_prob("data/test/simple.lp")
+            .unwrap()
+            .set_obj_integral()
+            .solve();
+        let status = model.status();
+        assert_eq!(status, Status::Optimal);
+
+        //test objective value
+        let obj_value = model.obj_val();
+        assert_eq!(obj_value, 200.);
+    }
+
     #[test]
     fn set_time_limit() {
         let model = Model::new()

src/scip.rs

@@ -97,6 +97,11 @@ impl ScipPtr {
         Ok(())
     }
 
+    pub(crate) fn set_obj_integral(&mut self) -> Result<(), Retcode> {
+        scip_call!(ffi::SCIPsetObjIntegral(self.raw));
+        Ok(())
+    }
+
     pub(crate) fn n_vars(&self) -> usize {
         unsafe { ffi::SCIPgetNVars(self.raw) as usize }
     }