So partial matching is a handy tool which it, which it often saves you a lot of typing at the command line. It's not particularly useful when you're pro, when you're writing out programs and functions but it's very useful when you're kind of working at the command like typing things as fast as you can. So the idea with partial matching is that it works with the double bracket and the single, and the dollar sign operator. So, suppose I have a list x which has an element in it called aardvark which is the sequence 1 through 5. And suppose typing out the word aardvark every single time is a bit of a pain so I'm just going to type the word a. Well, the way the dollar sign works by default is that it looks for it looks for a name in this list, that matches the letter a. In this case there's only one element. And so you get you get the word aardvark. And then it gives me the, the el, the object associated with aardvark, which is the sequence 1 through 5. So if I use the double bracket operator things are a little bit different. So what the double bracket operator expects, is that it's going to be, that the name that you pass it is going to be an exact match for one of the names in the list. So by default the double bracket operator doesn't do partial matching like the dollar sign does. So now when I pass x double bracket a what happens is I get null back, because there's no element of the list that has the name a. But there's a some, a second argument that you can pass to the dou, double bracket operator, which is the exact argument. And if you specify that exact equals false. And then when I pass at x double bracket a, it gives me the sequence 1 through 5, because that's the one that mat, matches the letter a the closest.