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hw04
functions calling your functions; loops

Due Apr.02 (Wed) 10:00; submit a file hw04.py (written in JES) to hw04-dropbox and turn in a hardcopy in class Apr.02.

Figure 1: An example of calling triZag

(6pts) In lab, we wrote a Turtle function zag : Turtle, int → None, which had a turtle draw a zag-shape of a given size end-to-end ¹. It leaves the turtle ended up facing the same way it started.

Your task is to write triZag : Turtle, int → None which takes a Turtle, and draws three zags, turning between them to complete a zaggy triangle, as in Figure 1. Leave the turtle facing the same way it started.
Figure 2: An example of calling zagLevel2

(8pts) Write the function zagLevel2 : Turtle, size → None which is kind of like zag², except that it instead of drawing shorter lines and turning, it draws shorter zags and turns! If the turtle starts facing North, the result would be as in Figure 2 (though the Turtle's color may differ, of course).
(4pts) On codingbat.com, complete the problem Python > String-1 > make_abba.
Account setup: Be sure to create/use a codingbat account using yourRadfordUserName@radford.edu, and that you have set, at some point, prefs > Share To is set to ibarland@radford.edu. (If you re-register sharing with me, it'll say you're already sharing, so no harm done.)

When you're done, paste your code into your hw04.py file. Include a comment immediately preceding the function, reporting “ codingbat test-cases didn't pass”, where the blank is filled in with a number (hopefully, the number will be 0!).

(6pts) On codingbat.com, complete the problem Python > String-1 > make_out_word.

You will want to include, in the part you type in to codingbat.com, our definition of substring:

# substring : string, int, int → string
#   Given some text, a start-index, and a stop-index,
#   return the characters of `txt` from `start` up until (but not including) `stop`.
#   Indices are 0-based.
#   Examples:   substring( "radford", 3, 6) = "for"
#               substring( "radford", 0, 3) = "rad"
#
def substring(txt, start, stop):
  return txt[start:stop]

Paste your code (and report # test cases that don't pass), as in the previous problem.

(6pts) Using JES's image-functions, write speckleAt : Picture, int, int → None which takes a Picture and x, y coordinates, and “speckles” the pixel at that location by setting its red component to be a random number in 0 up to (but not including) 256.
Hint: Here is an example of how to get a random number in the range 0 up to (but not including) 4; try typing it in JES's interactions (lower) pane:
import random random.randrange(4) random.randrange(4) random.randrange(4)
In your program-file itself (the top page), have the import statement just once, up near the top of your file.
Beware: randrange is not like range, despite the similar names (one returns a single integer; the other returns an entire list-of-ints that can be looped over). They are no more similar that Ford and Radford.
(8pts) Write speckleRow : Picture, int → None which is given a picture and a valid row-number (a y-coordinate), and speckles every pixel in that row — from column 0 up to (but not including) the picture's width. (This function should, of course, call speckleAt many times.)
(8pts) Write speckle : Picture → None which takes in a picture, and speckles it.
Clearly, this function should work by calling speckleRow on every single row in the picture (that is, row# 0 up to (but not including) the picture's height).
(extra credit: 8pts) Write a the turtle function polygon : Turtle, int, int → None which takes in a turtle, a number of sides n, and a size, and has the turtle draw an n-sided polygon where each side is the indicated size. Your function should leave the turtle at it's starting location and direction.
Calling this function

Hint: If you call your function to draw a large number of sides, you'll want to pass it a small number for the size, so that it stays on the screen. Turtles get a bit wonky if they run into the edge of the screen.

Extra: For a little further extra credit: have this function take in not the length-of-each-side, but rather the desired diameter (of the circumscribing circle). This will require some geometry/trig, to figure out how long a side should be based on the diameter!

¹Some people may have written a version which drew a zag-shape three times longer than the requested size, end-to-end. If that was you, you'll want to fix it. ↩

²If this is a level-2 zag, we might say that the original was a level-1 zag. After you complete this task, it's left as a fun self-task, to draw a level-3 zag. ↩

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hw04 functions calling your functions; loops

hw04
functions calling your functions; loops