A14.9 Project: the delivery robot

Build the designed program. The robot starts facing the charging wall, 71 cm away. The delivery bay is to the right of where it parks. Write these subroutines, and use them in this order: - gap_ok(gap): gap is a number of cm; returns True if it is from GAP_LOW to GAP_HIGH inclusive, otherwise False. - run_unit_tests(): tests gap_ok with exactly these five values, in this order: 16.9 (expected False), 17 (True), 20 (True), 23 (True) and 23.1 (False). For each, print test gap_ok(<value>): pass or test gap_ok(<value>): FAIL, then print unit tests: <passed> of 5 passed. - approach(target): target is the gap in cm to park at; drive towards the wall and return the gap read with distance() once stopped. Call it as approach(20). - sidestep(cm): move right cm centimetres. Call it as sidestep(30). - signal(): LED green and an 880 Hz note. - evaluate(gap, elapsed): gap is the value approach returned and elapsed is clock() read after signal(). Print SC1 gap <gap> cm: <result> using gap_ok, SC2 in the bay after <elapsed> s: <result> (met if elapsed is at most TIME_LIMIT), and SC3 signal: met, where each <result> is met or not met. Then print criteria met: <n> of 3, counting the criteria met. The whole program prints exactly ten lines. SC4 is checked by watching the run, so the program does not print it: do not touch the wall.

# the two lines every program starts with: the commands, then the robot
from bugbot import *
connect()

GAP_LOW, GAP_HIGH = 17, 23     # SC1, in cm
TIME_LIMIT = 30                # SC2, in seconds

def gap_ok(gap):
    pass

The hint students can ask for: Build it in the order of the design: write gap_ok and test it before the robot moves, then approach, then the sidestep and signal, and evaluate last. Keep a count of passed tests and of criteria met as you print each line, so the totals come from the counts.

A solution

# the two lines every program starts with: the commands, then the robot
from bugbot import *
connect()

GAP_LOW, GAP_HIGH = 17, 23
TIME_LIMIT = 30

def gap_ok(gap):
    return GAP_LOW <= gap <= GAP_HIGH

def run_unit_tests():
    tests = [(16.9, False), (17, True), (20, True), (23, True), (23.1, False)]
    passed = 0
    for value, expected in tests:
        ok = gap_ok(value) == expected
        passed += ok
        print(f"test gap_ok({value}): " + ("pass" if ok else "FAIL"))
    print(f"unit tests: {passed} of {len(tests)} passed")

def approach(target):
    while distance() > target + 10:
        forward(60, distance=5)
    while distance() > target + 1:
        forward(30, distance=1)
    return distance()

def sidestep(cm):
    right(50, distance=cm)

def signal():
    led("green")
    tone(880, 0.3)

def evaluate(gap, elapsed):
    results = [
        (f"SC1 gap {gap} cm", gap_ok(gap)),
        (f"SC2 in the bay after {elapsed} s", elapsed <= TIME_LIMIT),
        ("SC3 signal", True),
    ]
    met = 0
    for text, ok in results:
        print(text + ": " + ("met" if ok else "not met"))
        met += ok
    print(f"criteria met: {met} of {len(results)}")

run_unit_tests()
gap = approach(20)
sidestep(30)
signal()
evaluate(gap, clock())

Any program that meets the task's checks is marked correct in the simulator; this is one way, not the only way.