Python set comparison is operator
Is there a difference between "==" and "is"?
Bash is not finding a program even though it's on my path I'm creating a function where I need to pass an object so that it can be modified by the function. What is the difference between:  public void myFunction(ref MyClass someClass)   and  public void myFunction(out MyClass someClass)   Which should I use and why? Showing that $X^2$ and $X^3$ are irreducible but not prime in $K[X^2,X^3]$ Show that $X^2$ and $X^3$ are irreducible but not prime in $K[X^2,X^3]$.   My reasoning is as follows:  Since the only ways $X^2$ and $X^3$ can be factored in $K[X^2,X^3]$ are $X^2 = X^2 * 1$ and $X^3=X^3*1$ it follows that $X^2$ and $X^3$ are irreducible.  To show that they are not prime in $K[X^2,X^3]$ I argue that $X^2\mid X^3*X^3$ but $X^2\nmid X^3$ and $X^3\mid X^4*X^2$ but $X^3\nmid X^4$ or $X^3\nmid X^2$.  Is that correct? This appears to be related to the behavior originally suggested in .  It appears to be the same issue raised in , but this post has specific steps to reproduce the issue.  Here's what happened on one site in the network earlier today:   A question was posted much earlier Someone came along, and as an unregistered, new user with no other activity, posted a spam answer to that question at 04:36:54 UTC That same user posted a comment on their own answer with the same spam link at 04:37:31 UTC The answer was deleted as spam via community votes at 07:32:07 UTC A high-rep user saw the comment and raised a custom flag on it as being spammy at 07:32:54 UTC The unregistered user account was destroyed by a moderator at 08:13:10 UTC The comment now shows as "deleted by Anonymous" with a deletion time of 08:13:10 UTC The flag on the comment remains, but the only options are "Edit" and "Decline"; there is no "Delete" action   That there is no "Delete" action possible on the flag is reasonable, since the comment is now deleted. However, the flag is/was legitimate, so to decline the flag would be wrong. There's also nothing to leave while editing out the spammy part of the comment, as the comment consists solely of the same spam URL.  There is also no undelete option on the comment, so it's not possible to undelete the comment and then mark the flag as helpful by re-deleting the comment.  Effectively, this means that while the comment itself is effectively gone, the flag on it is in limbo and there is no good choice for what to do with the flag.  When deleting comments normally, my understanding is that any flags associated with those comments are automatically marked as helpful. However, it appears that the deletion of comments when destroying the user who posted them does not do that.  Therefore, I suggest that whenever comments are deleted as part of the owning user being destroyed, any pending flags against those comments should be marked as helpful at the same time.  It would also be a nice touch if those comments showed as deleted by Community♦, instead of Anonymous, but that's less of a concern in my case. What do the E and R prefixes stand for in the names of Intel 32-bit and 64-bit registers? Why do the measurements of this object seem erroneous? Where do I put the code snippets I found here or somewhere else on the web? Many posts here or somewhere else contain code, but they do not say where to put it.  Example:  I have found this post:  I'm a newbie with PHP. Where exactly should I place the code from the answer? Bootstrap 3 - Why is row class is wider than its container? Logical volume is not mounted but is in use. Please close all applications using this device (eg iscsi) How do I resize a LVM partition using system-config-lvm?  As per   I clicked on the partition and tried to resize, but got a pop-up error from system-config-lvm.     Logical volume is not mounted but is in use. Please close all applications using this device (eg iscsi).     What's the problem and how can I fix it?    See also . We have a directory and want to protect that from remove and rename, but we need to be able to rename, remove and create contents. What we can do? I am trying to understand   How can a set contain itself? Can you show example of set which is not a set of all sets and it contains itself. Change Error Message on FBA Login page On the default FBA Login Page, when a user enters wrong username/password an error message gets displayed:      "The server could not sign you in. Make sure your Username and Password are correct, and then try again.".    I want to change this error message to simple text      "Invalid Username and Password".    How can I achieve this? PPA seems to be constantly offline. Whenever I use sudo apt-get update, this error is shown:  W: Failed to fetch http://ppa.launchpad.net/ 404  Not Found   How do I fix these errors? Can I mill my opponent into defeat with Mindcrank and Duskmantle Guildmage? Okay the scenario I'm thinking of is as follows:   I control a ,  and 3 untapped lands (2 swamps, 1 Island to be perdantic). In my opponents turn he casts a burn spell to kill my duskmantle.   I activate his first ability in response.   The way I am hoping the following interactions will go is:   Duskmantles ability will hit the stack at the top and resolve The burn spell resolves dealing its damage to Duskmantle The burn spell card hits the graveyard and triggers the infinite loop for duskmantle and mindcrank killing my opponent Duskmantle perishes   Is this the way that the stack would pan out? Do I win in this situation regardless of the stack being correct or not above? (I am not fully familiar with how the stack really works in magic) You can see the cards from my deck . How to open Nautilus at current command line directory? I was wondering if anybody knew a command that would allow me to open a Nautilus (if that's the right name for the Ubuntu graphic/window explorer) window from the command line at the current directory that the user is at.  So, if I open a command line, and type:  cd /home/myUser/some/long/path/to/a/directory   Then, I'd like to be able to issue some command:  nautilus open-sesame   And have a graphic window opened to /home/myUser/some/long/path/to/a/directory. Is this even possible? I want to install the PyCharm IDE by JetBrains for Python (free community edition).  I managed to , but I do not know how to install it. Can you please help me? Is the empty set a group? Center of a group ring? Let $R$ be a ring with unity and let $G$ be a group. Then what is the center of the group ring $R(G)$? I feel that the center $Z(R(G))$ is $R(Z(G))$. I assumed if $x=\sum_{i=1}^{n} r_i g_i$, then it should commute with every element of $R(G)$. In particular it should commute with $g=1 \cdot g \in R(G)$ Thus we get $$\big(\sum_{i=1}^{n} r_i g_i\big)g=g\big(\sum_{i=1}^{n} r_i g_i\big)$$ Thus I get $$g_i \cdot g=g_i \cdot g \text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ } \forall g \in G$$ Hence $x \in Z(R(G)) $. Is this correct? When does HashSet 'add' method calls equals? Are Newton's "laws" of motion laws or definitions of force and mass?