Shapes Calculator Lab

In this lab you will build a small geometry calculator by defining a Shape interface and implementing it for three concrete types.

The interface

Shapes to implement

Circle

• Area: math.Pi * r * r
• Perimeter (circumference): 2 * math.Pi * r

Rectangle

• Area: Width * Height
• Perimeter: 2 * (Width + Height)

Triangle — using Heron's formula

• Perimeter: A + B + C
• Area (Heron's formula):
  1. Compute the semi-perimeter: s = (A + B + C) / 2
  2. Area = math.Sqrt(s * (s-A) * (s-B) * (s-C))

Helper functions

TotalArea(shapes []Shape) float64 Returns the sum of Area() for every shape in the slice.

Describe(s Shape) Prints: Shape: <String()>, Area: <area>, Perimeter: <perimeter> Use fmt.Printf with %.2f for the numeric values.

In main

Create and describe three shapes, then print the total area:

Expected output