What's the difference between an array and a set in Appian?

Question

When looking at the list of available functions I see there is a list for array and one for set. I've been working with appian for a bit but I seem to use both list of functions for any array type, whether it is a list of CDTs or a list of numbers. 
 So, could someone explain to me what the set data type is and how it differs from an array? 
 If it's been asked already please send me a link. I was unable to find an answer for this when searching the site.

Mike Schmitt · Answer

Off the top of my head I'm unaware of any differences. I believe a set *is* an array for most purposes with respect to appian functions. If you have any particular examples that are still confusing, maybe you can specify here and we can look into it.

jeremys · Answer

Hi, Looking at this page under the 'Array' dropdown: docs.appian.com/.../Appian_Functions.html It seems like the main difference between set and array functions is that array functions can be used to change the data in an array, whereas set functions can only be used to manipulate the data. Note that it mentions Set functions are used for arrays.

aloks0189 · Answer

Hi Jose H. as per my understanding, there is a difference between array and set in Appian. 
 1. Set or Set functions doesn't allow duplicate values in Appian as well as in Java. 
 Whereas array allows duplicate values. 
 Example: assume I have a variable local!data: {10,20}

Array function example

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append (local!data, local!data) -> {10, 20, 10, 20} 
 
 Set function example

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union(local!data, local!data) -> {10, 20} 
 Hope this helps.