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```
```pub fn is_zero(n: f32) -> bool {
n.abs() < 0.00001
}

/// This macro allows defining constraints using 'expression1 <= expression2'
///
/// # Example:
///
/// ```
/// use lp_modeler::dsl::*;
/// use lp_modeler::constraint;
///
/// let ref a = LpInteger::new("a");
/// let ref b = LpInteger::new("b");
///
/// let mut problem = LpProblem::new("One Problem", LpObjective::Maximize);
/// problem += 5*a + 3*b;
/// problem += constraint!(a + b*2 <= 10);
/// problem += constraint!(b >= a);
/// ```
#[macro_export]
macro_rules! constraint {
([\$(\$left:tt)*] <= \$(\$right:tt)*) => {
(\$(\$left)*).le(\$(\$right)*)
};
([\$(\$left:tt)*] >= \$(\$right:tt)*) => {
(\$(\$left)*).ge(\$(\$right)*)
};
// Stop condition: all token have been processed
([\$(\$left:tt)*]) => {
\$(\$left:tt)*
};
// The next token is not a special one
([\$(\$left:tt)*] \$next:tt \$(\$right:tt)*) => {
constraint!([\$(\$left)* \$next] \$(\$right)*)
};
// Initial rule: start the recursive calls
(\$(\$all:tt)*) => {
constraint!([] \$(\$all)*)
};
}```