Entering the set of the real numbers in STACK

Entering the set of the real numbers in STACK

by Stephan Bach -
Number of replies: 6

Hi,

in questions where students have to find the solution set of an equation it would be helpful if they could also enter the set of the real numbers, namely in a way, that Maxima also realizes it as a set.

The point is, that I would like to set Check_Type to true in the input options. Then the students have to enter a set and not a list or a single solution. But next to the empty set {} and any finite set like {1,2,3} also the set of the real numbers should be accepted. I was thinking of recommending "all" as the proper answer if the solution set was the set of the real numbers, but "all" is no set in Maxima.

Therefore if I then use the option Check_Type the students will not be allowed to enter a regular set and I basicly give away the solution, if I don't use the option Check_Type some will probably not type any set.

Is there any solution to this?

Stephan.



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In reply to Stephan Bach

Re: Entering the set of the real numbers in STACK

by Christopher Sangwin -
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Stephan,

I have already started work on better support for sets of real numbers, and yes "all" is already accepted by ATAlgEquiv to mean the set of all real numbers.

Could I ask you to look at the equivalence reasoning test cases, as many of these issues are documented there.

Test cases are here: https://github.com/maths/moodle-qtype_stack/blob/master/tests/fixtures/equivfixtures.class.php

A front end is here: https://github.com/maths/moodle-qtype_stack/blob/master/equivdemo.php

Internally, I have this code for real intervals:
https://github.com/maths/moodle-qtype_stack/blob/master/stack/maxima/intervals.mac
Please don't reinvent or work in parallel to this, but contributions are very welcome to improve this aspect of STACK.

I'm giving priority to STACK 4.3, rather than adding features.
Chris
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In reply to Christopher Sangwin

Re: Entering the set of the real numbers in STACK

by Stephan Bach -
Thanks Chris, this helped.
If I understand it correctly, then, if I check the students answer type, "all" and "none" are considered to be the same type of object as an equation or inequality. Therefore these symbols can easily be used as part of an equivalence reasoning.
But if the teachers answer is a set then the option of checking the students answer type will not accept "all" as a valid answer.
Stephan
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In reply to Stephan Bach

Re: Entering the set of the real numbers in STACK

by Christopher Sangwin -
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Stephen,

The relevant unit tests for the Algebraic Equivalence answer test are here:

https://github.com/maths/moodle-qtype_stack/blob/master/tests/fixtures/answertestfixtures.class.php#L274

So, there is no "set" as a teacher's answer which is equivalent to "all", but if the teacher has "x=x" then this is equivalent to "all".  

I'm very willing to discuss all this further, if you would like to propose sensible behavior if it is missing.

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In reply to Christopher Sangwin

Re: Entering the set of the real numbers in STACK

by Stephan Bach -

Thanks Chris,

this is good to know - I had seen this under the equivfixtures.

My idea was, that it would be great if one could create an input where only a real set (such as checked by realsetp) was accepted. Because then anything which syntactically actually is a set could be entered but nothing else and you leave it up to the student how the set is structured.

Stephan

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In reply to Stephan Bach

Re: Entering the set of the real numbers in STACK

by Christopher Sangwin -
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Yes Stephan,

We are about to refactor the input mechanism, and I think some much more flexible "type checking" will be part of that.  There are lots of situations where we want to provide a context in interpreting the student's answer.  Matti's hard work on the new parser make this all much more achievable now.

Chris


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In reply to Christopher Sangwin

Re: Entering the set of the real numbers in STACK

by Stephan Bach -
This sounds good. Thanks for your hard work!
Stephan
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