Merge pull request #9 from MrKonstantinT/clone-constraint

Derive Clone on Constraint Model.

src/math/expressions.rs

@@ -5,6 +5,7 @@ use Num;
 use math::variables::{AbstVar, new_const};
 use math::relationships::Relationship;
 
+#[derive(Clone)]
 pub struct Expression {
     left_hand_side: Vec<AbstVar>,
     relationship: Relationship,

src/math/relationships.rs

@@ -1,4 +1,4 @@
-#[derive(PartialEq, Debug)]
+#[derive(PartialEq, Debug, Clone)]
 pub enum Relationship {
     EQ,
     LEQ,

src/objective/constraints.rs

@@ -1,6 +1,7 @@
 use math::variables::AbstVar;
 use math::expressions::Expression;
 
+#[derive(Clone)]
 pub enum Constraint {
     Regular(Expression),
     NonNegative(AbstVar),