Functions

Name a piece of work

A function packages a calculation under a name, so you can run it again with different inputs:

def area(width, height):
    return width * height

print(area(2, 3))      # 6
print(area(0.5, 4))    # 2.0

• def starts the definition: the function's name, its parameters in parentheses, then a colon.
• The body is the indented lines underneath. Python uses the indentation (4 spaces) to tell which lines belong to the function.
• return hands a value back to whoever called the function. area(2, 3) runs the body with width = 2 and height = 3, and the whole call becomes 6.

Defining a function doesn't run it; calling it does.

return versus print

print shows a value to you. return gives it back to the program, which can store it or use it in more maths:

total = area(2, 3) + area(1, 1)    # 7

A function that only prints gives back None, Python's "nothing" value. The grader calls your functions and checks what they return, so always return the answer.

Every robot lesson is built this way: you'll write functions like forward_kinematics(q) that turn joint angles into a position.

Your task

1. Write deg_to_rad(deg) so it returns deg converted to radians.
2. Write reach(l1, l2) so it returns the reach of a two-link arm: the two lengths added together.

The starter calls both so you can see what they return. The grader tries each one on several inputs.