@PlaysDice Thank you sir yes. The linked answer here to the question I asked talks about tail specifically.

@YvesKlett In my opinion you should just make packagedata.net the topic of the main chatroom, BeginPackage["Chat", {" mathematica.stackexchange.com "}] is silly and serves no purpose.

@YvesKlett Probably this here?

@William Long time ago we kind of found out that it indeed serves a purpose: It seems that a good portion of people (including me) use the link to visit the main site directly when they are in chat.

@William huh?

Can anyone comment on this construction? cov[x_Symbol, x_Symbol] := var[x]

What is the purpose of separate slots for two x parameters?

It's from a very nice package given by Oleksandr in this answer.

@dionys The covariance of x with respect to x itself is the variance of x. It's convenient to define it this way, because then you can just apply cov everywhere and if it can be simplified to var that will happen automatically.

Note that f[x_, x_] does not match f[1,2] for example - this definition will only come into play if the two given arguments are the same.

@IstvánZachar Run["date > output.dat"] works for me on v10.0.2 on Ubuntu. The function returns '0' which means 'successful completion'.

@Pickett Thanks. That's a clever way to express it. I was looking at Patterns Involving Alternatives and it just wasn't clicking.

@PlaysDice Thanks Dice, but I explicitly wanted to solve it with RunProcess as it performs many other things that I don't want to do manually (check PrintDefinitions@RunProcess). I am aware of other solutions (cf. this thread).

@dionys {x_, x_} and {_, _} are not the same pattern. The former matches {1,1} but not {1,2}. The latter matches both.

@YvesKlett Apologizes, I misread the stared comments and sent it to the wrong person.

@Pickett In my opinion you should just make packagedata.net the topic of the main chatroom, leave the main site url if you would like and do something like mathematica.stackexchange.com Apps packagedata.net

@halirutan leave it if you would like it just seems like packagdata makes up half of the stared comments every time I take a look.

@William I'm glad you like PackageData, but I'm not a moderator in this chat room so I can't do it. Also I'm not willing to lobby for anyone else to do it, there are many projects that are worthy of attention like the IntelliJ plugin and MATLink but the description of the chat room isn't the place for it.

If anything I should think it will make users wonder if they are in the main chat room or if they are in the PackageData chat room.

@Pickett that's fair the I guess.

I still think it would be more appropriately used with a link to the main site and to packagedata.net then the useless mathematica plug that it is now

@Pickett :) both should be plugins on your site of course

@IstvánZachar fair enough. btw- what does PrintDefinitions@RunProcess do?

@PlaysDice You have to load it like this: Needs["GeneralUtilities`"]

When you have, PrintDefinitions@RunProcess will show you the source code of RunProcess (or the part of it that WRI has chosen to make available in this way, at least.)

what does WRI do to make function definitions unavailable to PrintDefinitions? Things like Nest aren't Locked but are still not readable.