"""
Exercise 6.9 from "A primer on..."
Change the input to a given function from a list to 
a dictionary, with integer keys 1, 2, 3. 
Solution:
1. First change the test function to use the new input type,
which makes the test fail
2. The change the actual function so that the test passes. 
"""


def triangle_area(v):
    [x1,y1] = v[1]; [x2,y2] = v[2]; [x3,y3] = v[3] 
    
    #or, more compact version:
    #[x1,y1], [x2,y2], [x3,y3] = v

    A = abs(0.5*((x2*y3)-(x3*y2)-(x1*y3)+(x3*y1)+(x1*y2)-(x2*y1)))
    return A

# Test function from book
def test_triangle_area():
	"""
	Verify the area of a triangle with vertex coordinates
	(0,0), (1,0), and (0,2).
	"""
	v1 = (0,0);  v2 = (1,0);  v3 = (0,2)
	#vertices = [v1, v2, v3]
	vertices = {1: (0,0), 2: (1,0), 3: (0,2)}
	expected = 1
	computed = triangle_area(vertices)
	tol = 1E-14
	success = abs(expected - computed) < tol
	msg = "computed area={computed:g} != {expected:g} (expected)"
	assert success, msg


"""
Terminal> pytest area_triangle_dict.py 
============================= test session starts ==============================
platform darwin -- Python 3.9.7, pytest-6.2.4, py-1.10.0, pluggy-0.13.1
rootdir: /Users/sundnes/Desktop/IN1900_13_okt
plugins: anyio-2.2.0, mock-3.10.0, cov-3.0.0
collected 1 item                                                               

area_triangle_dict.py .                                                  [100%]

============================== 1 passed in 0.01s ===============================
"""