Static Dispatch with a Trait Bound
10 points
Circle and Square already implement Shape (given, below — do not change them). Implement describe_shape, a generic function bounded by T: Shape, that returns "area = {area:.2}". Because T is fixed per call site, the compiler monomorphises a separate copy of this function for each concrete shape — no vtable involved.
Required signature
pub trait Shape { fn area(&self) -> f64; } pub struct Circle { pub radius: f64 } impl Shape for Circle { fn area(&self) -> f64 { std::f64::consts::PI * self.radius * self.radius } } pub struct Square { pub side: f64 } impl Shape for Square { fn area(&self) -> f64 { self.side * self.side } } pub fn describe_shape(shape: &T) -> String;Visible tests
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describes_circle#[test] fn describes_circle() { let c = Circle { radius: 2.0 }; assert_eq!(describe_shape(&c), "area = 12.57"); }
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