SICP exercise 2.02

From Drewiki

Problem

Consider the problem of representing line segments in a plane. Each segment is represented as a pair of points: a starting point and an ending point. Define a constructor make-segment and selectors start-segment and end-segment that define the representation of segments in terms of points. Furthermore, a point can be represented as a pair of numbers: the x coordinate and the y coordinate. Accordingly, specify a constructor make-point and selectors x-point and y-point that define this representation. Finally, using your selectors and constructors, define a procedure midpoint-segment that takes a line segment as argument and returns its midpoint (the point whose coordinates are the average of the coordinates of the endpoints). To try your procedures, you'll need a way to print points:

"("","")"

Solution

Points are pairs of numbers, and segments are pairs of points.

Here's the midpoint-segment procedure:

Tests:

Output:

(0,0)

Output:

(3,2)

Output:

(1,2)

Output:

(5,2)

Output:

(3,2)

Output:

(2.5,2)