How to use Union symbol in a response

I am trying to write questions in which students enter the domain of a function in interval notation. I have figured out a way for them to use the infinity symbol, by using a maple graded response with maple syntax and symbolic entry only. When I type "infinity" in the answer, the students can then answer the question using the infinity symbol in the equation editor. There is also a union symbol in the equation editor that I would like them to be able to use, but I have not been able to program it to accept the union symbol as a correct response.

Hi @devon_unlockmath, I found a question in the Precalculus content pack in the starter bundle: clone the question "1.2.1d Try It #2" from "Assignment 1.2 Domain and Range" in lesson "Chapter 01 Functions": Here's a link to the question. (Not sure if the link will work.)
In this question, the students are asked to do precisely what you want your students to do. Edit the question and look at the grade code. A particular library from the Maple repository is used that contains a "gradeInterval()" method. Very easy to use.

Writing grading code to accommodate for the union symbol can cause problems depending on which version of maplenet your are running. I would suggest a much easier approach: Have students use the letter "U" on the keyboard. This way you can simply do a string comparison.
For a domain question, you could try the following:
**** note1: the grading code was written to accomodate for "inf" as infinity if you were to modify the question.**** note2: the grading code ignores annoying extra spaces the student might add in.
link to .zip to import: https://naitcamy.sharepoint.c...
Preview:

Here is a question that uses the letter "U" to formulate a union of two intervals to specify the domain of a function:
The question(.zip) can be downloaded here: https://naitcamy.sharepoint.c...
***notes: the question ignores annoying spaces the student might add into their response
This is what the question looks like: