Bash : date -d throws "invalid date" when date is parameterized
Difference between ' and " on command line (bash)?
In ZF set theory the axiom of regularity (also called axiom of foundation) says that:     In all nonempty sets x there is an element y such that x∩y=∅   As I been told that  of the axiom is to prohibit constructions as $x\in x$, but is this a possible strategy?  Given a binary predicate $R$, written in infix notation, there are unitary predicates $p$ such that:  $\qquad \exists y \forall x: x R y \leftrightarrow p(x)$.  But there also are some convincing counterexamples:   $  p(x) \leftrightarrow \neg(x R x)$ $  p(x) \leftrightarrow \neg(x R f(x))$, where $f$ is any surjection $  p(x) \leftrightarrow$ all chains $x_1 R x, \: x_2 R x_1, \: x_3 R x_2,  \ldots \:$ are finite.   I think there is a major mistake to try to avoid certain paradoxical loops. First, there are no guarantees that every possibility is prohibited. And second, it seems pathological to make constructions that avoid certain proof-techniques (it's like the attitude of a shyster).  So, what protection comes from this axiom? Historically, has it anything to do with the Russell-predicate $x\notin x$?  See also Is there a way to find review articles by the keyword? When I search for papers using some keywords in academic databases (like Google Scholar), there are lots of papers, but I would like to read literature reviews first because I’m new in that area. (By literature reviews, I mean article-length papers that analyze existing work on a specific topic.)  So I think it would be helpful for me if there were a way to find literature reviews using the keyword or using the paper’s title. I want to categorize papers I’ve found by its document type (research, survey, review, etc).  What I've tried is using a specific academic database (ScienceDirect), which provides an advanced search, in which one can filter the paper by its type (original research article, review article, short survey, etc) – but I feel some limitations of this method. I think I can also do this by adding the word review to my keywords for searching or by reading a paper’s abstract, number of references and guessing whether it is review article or not.  Is there a more efficient way to find review articles by the keyword?  (My research area is computer science.)  UPDATE  "feel some limitations" in my post, I'm not sure but it seems that ScienceDirect only searches for literatures that belongs to ElseVier company. I think It doesn't cover the journal articles well, comparing to e.g) Google Scholar so I said I feel some limitations of it Can you get to blocked-in areas? Convert object string to JSON In , someone suggested in a  that I should not cast the result of malloc. i.e., I should do this: int *sieve = malloc(sizeof(int) * length);  rather than: int *sieve = (int *) malloc(sizeof(int) * length);  Why would this be the case? Reference for statistical mechanics from information theoretic view I am interested in knowing if some one here knows book/notes for statistical mechanics from the information theoretic viewpoint.  Additional Request from user83014  "Jaynes wrote a paper called Information theory and statistical mechanics (1957). I tried to read this but found it somewhat hard to follow, and I suspect it's because it's one of the earlier works, and that a modern text might be more refined since we've had time to work it out. On the other hand, what I've read from physics textbooks don't explicitly talk about information theoretic concepts like shannon entropy.  "Is there a good modern introduction to the information theoretic view of entropy?" I have looked everywhere for lava or obsidian in 0.7.1. I've looked all the way from top to bottom and all around, in about a 100 block diameter, but I can't find any. Where can I get some? Can less retain colored output? Can I get less not to monochrome its output?  E.g., the output from git diff is colored, but git diff | less is not. How to tell if a  tag failed to load I'm dynamically adding &lt;script&gt; tags to a page's &lt;head&gt;, and I'd like to be able to tell whether the loading failed in some way -- a 404, a script error in the loaded script, whatever.  In Firefox, this works:  var script_tag = document.createElement('script'); script_tag.setAttribute('type', 'text/javascript'); script_tag.setAttribute('src', 'http://fail.org/nonexistant.js'); script_tag.onerror = function() { alert("Loading failed!"); } document.getElementsByTagName('head')[0].appendChild(script_tag);   However, this doesn't work in IE or Safari.  Does anyone know of a way to make this work in browsers other than Firefox?  (I don't think a solution that requires placing special code within the .js files is a good one. It's inelegant and inflexible.) Inner join using an array column Having trouble indexing and executing a query in O (log n) time.  The query includes an INNER JOIN, an ORDER BY, and an equality operation. If I understand the laws of databases correctly, a query can be indexed and executed in O (log n) time (or thereabouts) if a non-equality operator is not used on more than one column. In this case, I believe the INNER JOIN does count as an equality operator and the non-equality operator would be the ORDER BY portion of the query. This table has upwards of 10,000,000 rows and needs to handle several reads and writes per second.  Using PostgreSQL. This is what the table looks like. As you can see, the column 'Names' is a list property and it is the column that the INNER JOIN goes against:  Age Names                       Date 34  ['carla', 'john', 'sam']    3/13/2011 26  ['json', 'cindy', 'joel']   3/13/2011 72  ['beth', 'amber', 'susie']  3/13/2011 14  ['john', 'jim', 'debie']    3/13/2011   This is the query that we are trying to do:  SELECT * FROM the_table WHERE Age==26 AND Names=='john' ORDER BY Date   My background is from using App Engine's Big Table, so I've used equality operators here to indicate that 'john' should be one of the names in the Names column. This would be an acceptable query in GAE's big table, it would execute in O (log N) time as all Big Table queries are reqyured to do. I am assuming there is a way to do this in PostgreSQL as well since PostgreSQL accepts list data types as columns.  Is this possible to do in PostgreSQL?  If so, how should the index be set up (we can't figure out how to set up an index that takes into account the three properties)? Copyright of a set of colors? I often see color combinations on webpages, images, posters, products etc. that harmonize really well. Am I allowed to use those colors in my own design?   This is solely about the colors. I will not use images, logos or shapes from that source, and my content is not related to the original color source. I am also far from any commercial aspect here. In Adobe Photoshop I am able to select multiple layers at once with Shift+Click.  How can I do that in GIMP? Finding what's using all the space in *nix Which sequence of commands will tell me which files are the largest starting from a particular directory, including all sub directories? I want to know where all the space went.  Preferably just with regular unix'y commands.  If possible, try to keep it compatible with Sun OS 5.10 (perhaps in addition to regular Linux answers, not as a replacement, to keep it as general as possible.) I have a website running in English and Japanese and the default language is Japanese.  What are the advantages of one over the other solution:   Solution 1. When accessing example.com, you will see only Japanese. When accessing example.com/en, you will see only English. Solution 2. When you access example.com, it will redirect you to example.com/ja, where you will see only Japanese. English site is still example.com/en. Show that the set $\mathbb{Q}[\sqrt{2}] = \{a + b \sqrt{2} \mid a, b \in \mathbb{Q}\}$ is a field with the usual multiplication and addition. What's the appropriate reaction to an answer that doesn't attribute the source it's copied from? Whats this white stuff on my board? Why are two universal objects isomorphic? Browsing some , it is claimed that two universal objects are isomorphic because they admit the identity morphism on themselves. But from two identity morphisms, how would you get an isomorphism between the two? By viewing the polynomials as a difference of two squares, factorise the following polynomial: $$x^4+x^2+1.$$ I searched but couldn't find a way to solve this  Edit: By using Hans Lundmark hint, I get:  $$(x^2+1)^2-x^2$$   Is it fully factorized? locale not found/setting locale failed - what should I do? I've installed Debian 7 i386 on my VPS (OpenVZ). Everything works fine, except locales - any attempt to install anything shows:  [...] perl: warning: Setting locale failed. perl: warning: Please check that your locale settings:     LANGUAGE = (unset),     LC_ALL = (unset),     LANG = "pl_PL.UTF-8"     are supported and installed on your system. perl: warning: Falling back to the standard locale ("C"). locale: Cannot set LC_CTYPE to default locale: No such file or directory locale: Cannot set LC_MESSAGES to default locale: No such file or directory locale: Cannot set LC_ALL to default locale: No such file or directory [...]   What I've tried:   Generating locales myself - update-locale LC_ALL="pl_PL.UTF-8" - shows:  apt-get install --reinstall locales  The same with dpkg-reconfigure locales + setting pl_PL.UTF-8, pl_PL.ISO-8859-2 or even en_US:  export LC_ALL=pl_PL.UTF-8 (even on root):  -bash: warning: setlocale: LC_ALL: cannot change locale (pl_PL.UTF-8)    Here is what shows locale:  root:~# locale locale: Cannot set LC_CTYPE to default locale: No such file or directory locale: Cannot set LC_MESSAGES to default locale: No such file or directory locale: Cannot set LC_ALL to default locale: No such file or directory LANG=pl_PL.UTF-8 LANGUAGE= LC_CTYPE="pl_PL.UTF-8" LC_NUMERIC="pl_PL.UTF-8" LC_TIME="pl_PL.UTF-8" LC_COLLATE="pl_PL.UTF-8" LC_MONETARY="pl_PL.UTF-8" LC_MESSAGES="pl_PL.UTF-8" LC_PAPER="pl_PL.UTF-8" LC_NAME="pl_PL.UTF-8" LC_ADDRESS="pl_PL.UTF-8" LC_TELEPHONE="pl_PL.UTF-8" LC_MEASUREMENT="pl_PL.UTF-8" LC_IDENTIFICATION="pl_PL.UTF-8" LC_ALL=   Nothing interesting found in /var/log. Even changing repo to official + purge and manual installation locales doesn't solve my problem, which manifests itself on each fresh installation of Debian 7.