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pag. 109-111


Pythagorean Theorem

The goal of incremental development is to avoid long debugging. By Pythagorean Theorem, the distance between two points is: \[d = \sqrt{(x2-x1)^2 + (y2-y1)^2} \]

Step 1

 
""" Step 1 / Incremental Development
    Define the function, with wrong answer but syntactically correct
"""

def distance(x1, y1, x2, y2):
    return 0.0

assert distance(1, 2, 4, 6) == 0.0
assert distance(1, 2, 1, 2) == 0.0
print("Asserts passed!")

Step 2

 
""" Step 2 / Incremental Development
    Find the differences x2-x1, y2-y1
"""

def distance(x1, y1, x2, y2):
    dx = x2 - x1
    dy = y2 - y1
    
    return 0.0

assert distance(1, 2, 4, 6) == 0.0
assert distance(1, 2, 1, 2) == 0.0
print("Asserts passed!")

Step 3

 
""" Step 3 / Incremental Development
    Compute the sum of squares
"""

def distance(x1, y1, x2, y2):
    dx = x2 - x1
    dy = y2 - y1

    sum = dx**2 + dy**2
    
    return 0.0

assert distance(1, 2, 4, 6) == 0.0
assert distance(1, 2, 1, 2) == 0.0
print("Asserts passed!")

Step 4

 
""" Step 4 / Incremental Development
    Finally, use math.sqrt() to compute the result
"""

import math

def distance(x1, y1, x2, y2):
    dx = x2 - x1
    dy = y2 - y1

    sum = dx**2 + dy**2
    
    return math.sqrt(sum)

d = distance(1, 2, 4, 6)

assert distance(1, 2, 4, 6) == 5.0
assert distance(2, 2, 2, 6) == 4.0
print("Asserts passed!")



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