regex for list comparing?

Question

I'm trying to filter out some objects based on an attribute property in C#. I've decided to do this based on comparing two comma delimited lists such that:

• "a,b,c" ~ "a,b,c", "a,c,b", "c,a,b", etc..
• "a,b,*" ~ "a,b,c", "a,d,b", "g,a,b", "a,b", etc..
• "a,b,c" !~ "a,c,d", "a,c", "a", etc..

I figure you should be able to do this with a simple regex match expression but I can't figure it out as yet.

Anyone know how to do this? In the mean time going to brute force it with code.

Thanks in advance

--EDIT

by ~ I mean equivalent, sorry for confusion.

also "a,b,c" could also be "abra,barby,candybar". Its not single characters but a list of values.

Answer 1

It's not a regular expression, but it's much simpler than any one could possibly be.

var attributes = input.Split(",");
var testCase = test.Split(",");

return attributes.All(x => testCase.Contains(x)) && testCase.All(x => attributes.Contains(x);

If you find a *, leave off one half of the && expression.

Answer 2

If you want a regex, here's my take on this:

^                       # match start of string
 (?=.*a(?:,|$))         # assert it matches a followed by a comma or end-of-str
 (?=.*b(?:,|$))         # assert it matches b followed by a comma or end-of-str
 (?=.*c(?:,|$))         # assert it matches c followed by a comma or end-of-str
 (?:(?:a|b|c)(?:,|$))*  # match a, b or c followed by a comma or end-of-str
$                       # match end of string

In case you find a .*, you keep the assertions but change the last part of the regex to allow it to match anything. Second example:

^                       # match start of string
 (?=.*a(?:,|$))         # assert it matches a followed by a comma or end-of-str
 (?=.*b(?:,|$))         # assert it matches b followed by a comma or end-of-str
 (?:[^,]*(,|$))*        # match anything followed by a comma or end-of-str
$                       # match end of string

---

Of course you'll still need to parse the string to generate the regex, and at this point I frankly would prefer to just use conventional code (it would probably be faster too), eg (pseudo code):

setRequired  = Set(csvRequired.Split(','))
setActual    = Set(input.Split(','))

if (setActual.Equals(setRequired)))
{
    // passed
}

If you find the asterisk, just remove it from setRequired and use .Contains instead of Equals