What you learn today
- Assess other people's code
- Make a list of issues
- Justify improvements
A fellow player sends you his script: “The lab heating is acting up, can you take a look?” Twelve lines, looks tidy. A good review still finds four bugs – because it follows a fixed list instead of gut feeling.
Assessing other people's code
Always go through in the same order:
| Check | Question |
|---|---|
| 1. Does it run permanently? | endless loop, yield in every loop, no program end |
| 2. Does it read correctly? | fitting batch mode (Average for temperatures, Sum only for real sums) |
| 3. Does it calculate correctly? | comparisons in the right direction, units (kelvin, share instead of percent) |
| 4. Does it fail safely? | what happens on NaN, on a missing device? |
| 5. Does it keep the limits? | 128 lines, 90 characters, 4096 characters |
| 6. Is it readable? | defines, aliases, sections, labels instead of line numbers |
The first four points decide whether the plant works. The last two whether anyone still understands it in three weeks.
Making an issue list
Write down every finding with line, problem, consequence and suggestion:
| Line | Problem | Consequence | Suggestion |
|---|---|---|---|
| 9 | Sum for temperature | two sensors report 580 K, heater never on | Average |
| 9 | no yield | 128 passes with the same value | yield after start: |
That way the other person can follow every point instead of just hearing “it is wrong”.
Justifying improvements
“Do it differently” convinces nobody. “With Sum the chip adds up the temperatures as soon as a second sensor is built – hence Average” does. Every change needs a reason from the game: which situation, which damage.
lbn temp SENSOR HASH("Labor") Temperature Average # not Sum
slt tmp temp OFF_AT # heater: slt, not sgtA wrong Sum only shows up when a second sensor with the same name is built. With one sensor Sum and Average are the same. So in a review never ask “does it run right now?” but “does it still run after the next rebuild?”.
Also check what is not in the code. A missing NaN guard shows up on no line – only in the question “what happens when the sensor is gone?”.
Exercise
Task
The starter code is the fellow player's script. It has four bugs: wrong batch mode, swapped hysteresis, missing yield and – depending on the bug – no safe reaction to a missing sensor. Find and fix them.
- Heater “Labor” on below 18 °C, off from 22 °C (average of all sensors “Labor”)
- Sensor gone: heater off
Hints
Hint 1
Two sensors with Sum give double – Average.
Hint 2
A heater switches on when it is colder: slt instead of sgt.
Hint 3
yield right after start:. With slt NaN switches the heater off by itself.
Quiz
4 questions. You pass from 60 % – the server does the grading.
Complete the day
- Passed the simulator exercise
- Passed the quiz with at least 60 %
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