A notation question

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Christian Lawson-Perfect

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Oct 23, 2020, 5:33:28 AM10/23/20
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Hi all,
I've come across this problem while proofreading someone else's questions. The author has used the variable `x_0` in the answer to a mathematical expression part. I expect that some students will just type `x0` without an underscore if they're not told explicitly what to do.
Numbas accepts both forms, and they're both rendered exactly the same, but they're not considered to represent the 'same' variable.
I wonder if they should be considered identical. I think my preferred way of implementing this would be to normalise the version without an underscore to the version with, during parsing.

Does anyone have any objections to that, or suggestions for other solutions?

Julia Goedecke

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Oct 23, 2020, 5:39:59 AM10/23/20
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Hello Christian,
I vote in favour. I've tried to do this with alternative answers and also instructions to students, but if you have several such variables in the same gap it gets a bit much with all the combinations. So your solution would be much easier, and I can't think of a situation where one would have to use x1 and x_1 as different things: since they display the same, it would be not fair on the students in any case, as they cannot distinguish in the preview of their answer.

Julia 

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svda...@gmail.com

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Oct 29, 2020, 9:01:31 AM10/29/20
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I think it's a good idea to normalise one format to the other, if there's a simple way to do this. Either solution (x_0 -> x0 or x0 -> x_0) will be useful once we all understand that's how it works. I have a preference for the underscore version. This is because I might want to use $A_{xy}$ as a variable: A_xy seems clear and will be rendered properly, whereas Axy will not. Cheers, Simon

Jonny Rae

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Oct 29, 2020, 10:57:26 AM10/29/20
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I think this would be a good idea - I had a couple of students lose marks because of this a few weeks ago. Nothing I couldn't rectify of course, but still.

Jonny

Christian Lawson-Perfect

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Feb 24, 2021, 5:08:35 AMFeb 24
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I've just spotted this thread in my inbox. I thought I'd mentioned this at the time, but apparently not. Names like x0 and x_0 are now considered to be equivalent by the "mathematical expression" part marking algorithm.

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