Unprotect fails the first time, works on second pass
How to unprotect GeneratingFunction
Getting No module name exifread error from QGIS Photo2Shape plugin? I'm getting a NoSuchMethodError error when running my Java program.  What's wrong and how do I fix it? I want to ask about two sentences, and what would be the correct way to form a question:   It's very important that we eat healthy food, ...........?  Which would be the correct question tag: (isn't it) or (don't we)? It's a must that all applicants follow the rules of the competition, ..........?  Which would the correct question tag: (don't they) or (mustn't they)?   Please could you tell me the correct answers, and, more importantly, why those are correct? Let's say that there is a question asked in a bad manner, in a way that the question is missing. For example the user shows the code and doesn't explain very well which is the problem.    Usually someone starts digging in the OP mind posting comments and asking him for details. It may happen that the question gets edited and the OP edits it to a valid question.    Do you usually give the OP time to edit the question or you immediately vote to close it? Order of a homomorphism of groups In categorical terms, why is there no canonical isomorphism from a finite dimensional vector space to its dual? I've read in several places that one motivation for category theory was to be able to give precise meaning to statements like, "finite dimensional vector spaces are canonically isomorphic to their double duals; they are isomorphic to their duals as well, but not canonically."  I've finally sat down to work through this, and -  Okay, yes, it is easy to see that the "canonical isomorphism" from $V$ to $V^{**}$ is a functor that has a natural isomorphism (in the sense of category theory) to the identity functor.  Also, I see that there is no way that the functor $V\mapsto V^*$ could have a natural isomorphism to the identity functor, because it is contravariant whereas the identity functor is covariant. My question amounts to:     Is contravariance the whole problem?   To elaborate:   I was initially disappointed by the realization that the definition of natural isomorphism doesn't apply to a pair of functors one of which is covariant and the other contravariant, because I was hoping that the lack of a canonical isomorphism $V\rightarrow V^*$ would feel more like a theorem as opposed to an artifact of the inapplicability of a definition.  Then I tried to create a definition of a natural transformation from a covariant functor $F:\mathscr{A}\rightarrow\mathscr{B}$ to a contravariant functor $G:\mathscr{A}\rightarrow\mathscr{B}$. It seems to me that this definition should be that all objects $A\in\mathscr{A}$ get a morphism $m_A:F(A)\rightarrow G(A)$ such that for all morphisms $f:A\rightarrow A'$ of $\mathscr{A}$, the following diagram (in $\mathscr{B}$) commutes:  $$\require{AMScd}\begin{CD} F(A) @&gt;m_A&gt;&gt; G(A)\\ @VF(f)VV @AAG(f)A\\ F(A') @&gt;&gt;m_{A'}&gt; G(A') \end{CD}$$  This is much more stringent a demand on the $m_A$ than the typical definition of a natural transformation.  Indeed, it is asking that $m_A=G(f)\circ m_{A'}\circ F(f)$, regardless of how $f$ or $A'$ may vary. Taking $\mathscr{A}=\mathscr{B}=\text{f.d.Vec}_k$, $F$ the identity functor and $G$ the dualizing functor, it is clear that this definition can never be satisfied unless $m_V$ is the zero map for all $V\in\text{f.d.Vec}_k$ (because take $f$ to be the zero map). In particular, it cannot be satisfied if $m_V$ is required to be an isomorphism.     Is this the right way to understand (categorically) why there is no natural isomorphism $V\rightarrow V^*$?   As an aside, are there any interesting cases of some kind of analog (the above definition or another) of natural transformations from covariant to contravariant functors?  Note: I have read a number of math.SE answers regarding why $V^*$ is not naturally isomorphic to $V$. None that I have found are addressed to what I'm asking here, which is about how categories make the question and answer precise. ( was closest.) Hence my question here. How to get the file name from a full path using JavaScript? Is there a way that I can get the last value (based on the '\' symbol) from a full path?  Example:  C:\Documents and Settings\img\recycled log.jpg  With this case, I just want to get recycled log.jpg from the full path in JavaScript. What's the maximum value for an int in PHP? Ignoring the special libraries that allow you to work with very big numbers, what's the largest int value you can store in PHP? Destroying a spammer does not delete their comments Weird sharp vertices with subdivision modifier I have a simple skull model, to which I applied the subdivision modifier. For the most part everything works as expected, except I keep getting these weird sharp vertices and I can't seem to figure out how to flatten them.    I'm using Blender 2.8. Is this some kind of feature I can disable/enable for particular vertices? The distance between the sharp vertices and the gray outline differ.    Any suggestions please? Thank you!  EDIT: I also tried selecting as both - vertexes and edges and then applied Edge->Clear Sharp, but nothing changed. Inequality between $\ell^p$-norms Bluetooth earphones work fine until sleep. After resuming from sleep however, they appear to connect for a brief moment before disconnecting. On blueman, the error given is Resource temporarily unavailable. This issue arose only after updating to 18.04 LTS.   Here's the terminal output for lsusb:  Bus 001 Device 002: ID 8087:8001 Intel Corp.  Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub Bus 003 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub Bus 002 Device 004: ID 1bcf:0002 Sunplus Innovation Technology Inc.  Bus 002 Device 003: ID 04f2:b477 Chicony Electronics Co., Ltd  Bus 002 Device 002: ID 0a5c:21f1 Broadcom Corp. HP Portable Bumble Bee Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub Prove that $PSL(2,\mathbb{Z})$ is free product of $C_2$ and $C_3$ Prove that $PSL(2,\mathbb{Z})=C_2 \star C_3$.  Now $C_2 \star C_3=\langle a,b\ |\ a^2, b^3 \rangle$ i.e. the free product.  But how do I show that presentation of $PSL(2,\mathbb{Z})$ is this? Is Mana Weaving ok if it's followed by a thorough shuffle? My friends and I are relatively new to MtG. At some point, one of them introduced us to the idea of mana weaving, and we'd do this to declump our decks prior to a very thorough shuffling. However, at the Theros pre-release, one of us was asked not to do this, and we learned it was frowned upon and ceased to do it.  I just now came across , and it sounds like mana weaving's only bad if you use it to leave your deck in an even distribution, and it's OK if your deck is then thoroughly shuffled. In hindsight, the judge may have simply thought my friend wouldn't have shuffled afterwards, but at the time I came under the impression it was frowned upon even if you did shuffle afterwards.  So: is mana weaving my deck OK, if I shuffle it very thoroughly afterwards? Stop Edit/Rollback Wars: Limit Number Of Edits/Rollbacks Per User Per Post Per Day I came up with an idea for how to begin putting an end to the edit/rollback wars and then the ensuing comments battle...   What if you are only allowed to edit a post (not the author) once a day. What if you are also only allowed to rollback one edit to your post a day. There would not be a overall limit on the users ability to edit other posts other than the one edit per post per day. There would also not be a limit on the number of times a single post could be edited or rolledback (multiple users), but each edit/rollback would trigger the 24 hour wait... There is currently some threshold in place that allows a post to be edited after it is posted without calling it an edit.  This same threshold could apply to the edit in case a mistake is made (fat fingered, mis-tagged, etc.) which would allow the editor a window of time to correct a mistake before getting locked out.     If either the editor or rollerbacker feel that the current state of the post is not acceptable and they are out of mods for the day, then a moderator can get flagged through the current process. How can I watch Amazon Prime videos using Firefox on Ubuntu 16.04? How can I watch Amazon Prime videos using Firefox on Ubuntu 16.04? Currently Firefox version is 48.0. When I attempt to watch a video, I get the following Digital Rights Error message:  Your web browser is missing a digital rights component. In your web browser’s address bar, type about:addons, press Enter, and then on the left, click Plugins. For the Widevine Content Decryption Module, select Always Activate, and then refresh the video’s page and try watching the video. If the video doesn’t play, go back to Plugins, click the gear icon at the top of the page, and then click Check for Updates. When the plugins have updated, refresh the video’s page, and then try watching the video.  I didn't find Widevine Content Decryption Module. I searched for a solution, but it didn't work... One solution I found was to sudo apt-get install flashplugin-installer and then do the following: sudo apt-add-repository ppa:flexiondotorg/hal-flash sudo apt-get update &amp;&amp; sudo apt-get install libhal1-flash  However, it didn't work and I still got the same Digital Rights Error message. I am able to watch Amazon Prime videos using Google Chrome, but not with Firefox. I want to know if it's possible on Firefox on Ubuntu 16.04. I have no root access on this machine.  I would like to know if there is a way I can download Ubuntu packages and install them as non-root?  Probably in my ~/bin or ~/usr/share or something like that? Would that work? Recursively replace string in files I want to replace the backslash in the string page_path\example_filename.txt with a forward slash.  I also want to be able to run this on a large file system and have it recursively search all directories.  I found someone on the web who said to use grep, xargs, and sed but I wasn't able to get it to work. I've been trying different variations on delimiters and escape characters, but didn't get it.  Here is the command I was trying to run: grep -lr -e 'page_path\\' * | xargs sed -i 's/page_path\/page_path//g'  Thanks in advance. How to remove Home Folder icon from desktop in Ubuntu 20.04? When I start Ubuntu I had my &quot;home/user&quot; in my Desktop. test is my User.   How do I make the folder not be on the desktop? If I have a 18-55mm lens, is there a point in buying a 35mm prime lens? I have the Nikon kit lens that came with a D5100 — the kit lens is  . I was thinking of getting a fast lens and I am looking to buy the .  Should I consider 35mm or instead buy a 55-200mm for better range?