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Java Code Reading Question

Re: Java Code Reading Question

by Richard Lobb -
Number of replies: 0

Hi Andreas

That's an interesting example.

I'm afraid that changing the order of Twig evaluation of the various fields of the question wouldn't help. When the question is first initialised, the template parameter field is evaluated by Twig (in your case). The result is a JSON record that provides a set of variables which then provide the environment for all subsequent Twig evaluations, namely the question text, each test case etc and ultimately, when the question is submitted, the template itself. However, all those evaluations are independent - there is no state preserved across the different evaluations. So changing the order in which fields of the question are evaluated wouldn't help. It's just not possible to have the global extra expanded by Twig and then to use that expanded version in a subsequent field of the question.

To make your approach work you would need to define the function func in the template parameter field. But the template parameters are JSON, and JSON doesn't allow proper multiline strings, which would make any attempt to define your multiline func very clumsy and unmaintainable. Which is, I assume, the reason you put it into the global extra instead.

BUT ... there is a solution! The latest version of CodeRunner (4.0.1) allows you to use languages other than Twig for constructing randomised template parameters. See here. Python would be my choice. If you select python3 as the template parameter preprocessor you can write your template parameters as

import sys, json
from random import seed, randint

args = {param.split('=')[0]: param.split('=')[1] for param in sys.argv[1:]}

operators = ["<", "<=", ">", ">=", "==", "!="]
val1 = randint(0, 4)
val2 = randint(0, 4)
val3 = randint(10, 50)
val4 = randint(10, 50)
val5 = randint(10, 50)
var = operators[randint(0, len(operators)) - 1]  # Unused?

func = f"""public int func()
    int[] arr = {{ {val1}, {val2}, {val3}, {val4}, {val5} }};
    int sum = 0;
    int x = 0;
        sum += arr[x];
    }} while (sum < 40);

    return sum;

print(json.dumps({"func": func}))

The output of that Python program is a JSON template parameter string that just defines the single value func. It is a little clumsy that the Java braces all have to be doubled to prevent their being interpreted as Python f-string format characters, but is otherwise workable enough?

With that approach, your question text is now just

Enter the return value from the function func() in the field below!

{{ func }}

This new preprocessor capability is still somewhat experimental but we've used it a bit in a course with over 1000 students and it worked perfectly. I attach an xml export of your question written that way.

You'll see that there are several warnings about using non-Twig preprocessors in tests and exams. However, if you're using Java questions, I think you're far more likely to overload the Jobe server with actual Java submissions in a test than by using a Python preprocessor. I would suggest, though, that using Java as the preprocessor (which is also possible) would be asking for trouble in tests and exams.