Shape Area in Rust

You write the common part of three shapes, and each shape's area.

Rust has no abstract classes. As in the abstract-classes lesson, a trait plays that role. The trait Shape has two methods with no body:

• area returns the shape's area as an i32.
• name returns the shape's name as a String.

It also has a default method, describe. It returns a text such as Square with area 25. That is the name, then with area, then the area.

Three structs implement Shape:

• Rectangle has a width and a height. Its area is width × height.
• Square has a side. Its area is side × side.
• RightTriangle has two sides a and b that meet at a right angle. Its area is a × b / 2, rounded down.

Their new functions and name methods are already written. You write each area.

For each shape, the harness prints describe() on its own line.

Example 1:

Input: Rectangle::new(3, 4), Square::new(5), RightTriangle::new(3, 4)
Output:
Rectangle with area 12
Square with area 25
Right triangle with area 6

Explanation: 3 × 4 = 12 and 5 × 5 = 25.
The triangle is half of 3 × 4, so 6.

Example 2:

Input: RightTriangle::new(3, 5), Square::new(1)
Output:
Right triangle with area 7
Square with area 1

Explanation: Half of 3 × 5 is 7.5.
It rounds down to 7.

Example 3:

Input: Rectangle::new(1, 7), RightTriangle::new(1, 1)
Output:
Rectangle with area 7
Right triangle with area 0

Explanation: A 1 by 7 rectangle has area 7.
Half of 1 × 1 rounds down to 0.

Constraints:

• 1 to 100 shapes.
• Each size is a whole number from 1 to 10,000.