CPSC 425 Assignment 1
Intro to Scheme
Due Before Class on Wednesday, January 14^th

1. Download and install scheme PLT Scheme for your computer and read sections 1 and 2.1 through 2.2.5 of the PLT Scheme Guide.
2. Write a procedure in Scheme called distance that takes four parameters, x1, y1, x2, and y2, that represent the x and y coordinates of two points. The procedure should evaluate to the distance between the two points. If any of the procedure's arguments are not a number, then the procedure should evaluate to a string that states that the input is invalid.

Submission: Submit a scheme file containing your code on the course blackboard site.