Description
This lab explores modular program development using functions (See: Lec. 3B).
You will write simple functions to draw line segments and arcs and then use these
functions to draw a flower with a stem. See examples below.
• Any effort is fine – you will have a chance to improve on your art another time.
• The purpose is to build a little drawing library and to have a bit of fun doing
it.
• Make sure to test each function before proceeding.
(a) 5 Petals. (b) Lopsided (c) A good effort.
Figure 1: flowers.
Ex. 1 Write a function polyLine(. . .) that draws n line segments, each of the
same fixed length, each at an angle θ to the previous. The function should accept
the following parameters: a turtle t, the number of segments n, the length of each
segment length, and the angle each segment is tilted to the previous one angle. If you
are unsure how to pass values into a function, see the example programs in lecture
3A. The output for 5 segments, each of length 50, each tilted at 20o
to the previous:
Test your function before proceeding.
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It is good practice to put a description of the function just after the name. e.g.
def polyLine(t, n, length, angle):
’’’Draws ’n’ line segments of ’length’; tilted at ’angle’ to the prev. ”’
note the triple quotes – they allows for multi-line comments. Triple quoted strings at
the tops of functions are known as docstrings.
Ex. 2. Use polyLine(. . .) to a construct a function polygon(t, numSides).
Ex 3 Write a function drawArc to draw an arc of circle of radius r, subtended by an
angle α. The example below shows the arc of a circle of radius 100 in blue subtended
by α = 90o
You must use polyLine(. . .) to write drawArc.
The arc length s = r · α where α is in radians.
Break up the arc into (an integer) number of st. line segments n of a small fixed
length (∼ 5 pixels). Therefore each line segment of the arc will be of length = s/n
Call polyLine(. . .) with the above parameters to draw the arc
Ex. 4 Use drawArc(. . .) to define a function drawCircle(t, r) (r is the radius
of the circle).
Ex. 5 Define a function drawPetal(. . .). A petal is drawn by making two calls to
drawArc(. . .), appropriately flipping the turtle heading between the calls.
Ex. 6 Define drawStem(t, length, heading). Which draws a stem, a straight line,
coloured brown.
Ex. 7 Finally, define drawFlower(t, r, angle, numPetals, p) which makes numPetal
calls to drawPetal(. . .), each turned an angle p away from the previous).
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Ex.8 Finally, using the function above, draw a flower. Your result may look like one
of the flowers shown at the beginning of the lab. The individual parameter settings
will result in different flowers.
Bonus for very nicely drawn flowers! Esp. those that incorporate more colours, new
elements etc..
• Zip into a folder and submit!
