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• Throwing an AggregateException in my own code

  - by Pat

  How should I go about collecting exceptions and putting them into an AggregateException to re-throw? For my specific code, I have a loop and will have zero or more exceptions thrown from a part of the code. I was hoping to just add the new exceptions to the AggregateException as they arise, but the documentation sort of indicates that it should be constructed with all the Exceptions at once (there is no method to add an Exception to the object). And what about creating a new AE every time and just including the previous AE in the list of exceptions? Seems a hokey way to do it. Any better ideas?

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• Where should I handle the exceptions, in the BLL, DAL or PL ?

  - by Puneet Dudeja

  Which is the best place to handle the exceptions ? BLL, DAL or PL ? Should I allow the methods in the DAL and BLL to throw the exceptions up the chain and let the PL handle them? or should I handle them at the BLL ? e.g If I have a method in my DAL that issues "ExecuteNonQuery" and updates some records, and due to one or more reason, 0 rows are affected. Now, how should I let my PL know that whether an exception happened or there really was no rows matched to the condition. Should I use "try catch" in my PL code and let it know through an exception, or should I handle the exception at DAL and return some special code like (-1) to let the PL differentiate between the (exception) and (no rows matched condition i.e. zero rows affected) ?

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• Java Wicket - Calling javascript ( JQuery ) before AJAX

  - by user1428051

  I got this thing i'm trying to solve: I got a ListView created using Wicket ( 1.5 ) with a lot of elements and a scroll. When new items are available, the user is asked if he would like to refresh the list via a message backed by an AjaxLink: public void onClick(AjaxRequestTarget ajaxTarget) { /* do something ... */ ajaxTarget.addComponent(_list); } So on click the list gets reloaded and the scroll position is reset to zero. Is there any way i can call JavaScript before the list reloads the save the scroll position? (I know how to get/save the scroll position ( .scrollTop() ) , i just don't know how to call a function right before AJAX ).

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• mysql count(*) left join group by - the number of files in a folder

  - by Flavius

  Hi I have the following tables CREATE TABLE `files` ( `fileid` int(11) NOT NULL AUTO_INCREMENT, `filename` varchar(255) NOT NULL, `filesize` int(11) NOT NULL, `folder` int(11) NOT NULL, PRIMARY KEY (`fileid`) ) ENGINE=MyISAM DEFAULT CHARSET=utf8; CREATE TABLE `folders` ( `directoryid` int(11) NOT NULL AUTO_INCREMENT, `directoryname` varchar(255) NOT NULL, PRIMARY KEY (`directoryid`) ) ENGINE=MyISAM DEFAULT CHARSET=utf8; How to get a list of all folders and the number of files they hold, including folders who have no (zero) files? Recursion must not be taken into account. Found it select folders.directoryid, folders.directoryname, count(files.fileid) as no_files from folders left join files on files.folder = folders.directoryid group by folders.directoryid, folders.directoryname I hope it will help someone.

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• Keeping Score in XNA Game

  - by Seven

  Hi. I'm following an XNA tutorial and have the following code for collision detecting (detecting when a bullet collides with a target). Basically I'm looking to increment a score variable to display the score to the screen without re-writing the whole program. No matter where I place it in this method it seems to start incrementing from the number of targets, not from zero. Is there something simple I'm missing here? Any help would be greatly appreciated. Thanks. private CollisionType CheckCollision(BoundingSphere sphere) { if (completeCityBox.Contains(sphere) != ContainmentType.Contains) return CollisionType.Boundary; for (int i = 0; i < targetList.Count; i++) { if (targetList[i].Contains(sphere) != ContainmentType.Disjoint) { targetList.RemoveAt(i); i--; AddTargets(); return CollisionType.Target; } } return CollisionType.None; }

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• convert function from Access SQL to T-SQL 2005

  - by Pace

  Can someone please convert this access sql function for me to work in t-sql 2005. I am tring to take the selling price minus the cost as one number. And divide that by the original selling price to produce a second number Thanks :) =IIf([Selling Price]=0,0,([Selling Price]-Nz([Cost]))/[Selling Price]) IIRC it should be something along the lines of; ISNULL((ISNULL([Selling Price],0) - ISNULL(Cost,0)),0) / ISNULL([Selling Price],0) AS Margin But here I am getting a divide by Zero error. any suggestions?

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• DAQ Triggers in Matlab

  - by RidePlanet

  I'm writing a program that detects the speed of a object by hall effect sensors that are run into MATLAB through a DAQ (MCC USB-1408FS) The problem that has arisen is that I'm using a non-stop scan technique to detect the state of one of 3 sensors. Unfortunately this means that unless the object is rotating past each sensor at the exact rate the program runs, I will see an instantaneous speed (done by comparing the time between two sensors) of zero. I need the sensors to signal the program to count when they are hit, instead of constantly scanning for the signal. How can this be done?

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• Get "2:35pm" instead of "02:35PM" from Python date/time?

  - by anonymous coward

  I'm still a bit slow with Python, so I haven't got this figured out beyond what's obviously in the docs, etc. I've worked with Django a bit, where they've added some datetime formatting options via template tags, but in regular python code how can I get the 12-hour hour without a leading zero? Is there a straightforward way to do this? I'm looking at the 2.5 and 2.6 docs for "strftime()" and there doesn't seem to be a formatting option there for this case. Should I be using something else? Feel free to include any other time-formatting tips that aren't obvious from the docs. =)

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• Proper chart scaling in Reporting Services 2005

  - by lastas

  I'm developing a simple bar-chart in Reporting Services 2005 with a stored procedure as data-source. The values in this graph can be both positive and negative, and can span a very big range, and hence I cannot specify any non-dynamic scale that will work for all scenarios. The problem I'm facing is that the automatic scaling pretty much sucks. I get no line to show where the zero-point is, and the y-scale labels are from top to bottom: 8818 -191181 -391181 etc etc... So my question is, what is the best approach to make the scale more adapted to human reading? Is there any guide out there? Does reporting services 2008 handle this better? Also, moving away from Reporting Services is not really an option. I realize how to put values and expression in the max, min, and the gridline interval fields, although its more of a question what expressions I should put there.

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• Problem with Nulls and an UPDATE statement

  - by Dave

  UPDATE TableA SET Value = a.Value * b.AnotherValue FROM TableA AS a INNER JOIN TableB AS b WHERE (Condition is true); Here is the problem. The Value field for TableA does not allow nulls. If the calculation of a.Value * b.AnotherValue yields a null, an error is thrown. Now the question. Is there any way to tell the UPDATE to ignore the SET phase when the result of the calculation is a null and delete the record rather than updating it. This UPDATE is intended to update hundreds of records at a time but will fail if a single null is encountered. Also, please note that using the ISNULL() function and setting the Value to zero is not acceptable. I would like the record to be dropped if a null is encountered. Many thanks in advance for any help rendered.

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• Need help with this question: Write Java code which reads numbers from the keyboard.....

  - by Chris

  Write Java code which reads numbers from the keyboard until zero is entered. Only the positive numbers entered are to be added to a variable-sized collection. This is what I have so far: import java.lang.*; import java.util.*; import java.io.*; import java.net.*; public class Demo1App extends Object { public static void main(String[] argStrings) throws Exception { ArrayList myArrayList = new ArrayList(); Scanner input = new Scanner(System.in); System.out.println ("NUMBERS:"); while (int input > 0) { myArrayList.add(input); } while (int input < 0) { System.out.println ("ENTER NUMBERS GREATER THAN 0!"); } } } This code doesn't work, I'm not sure why but any help with it would be appreciated.

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• binary number comparison

  - by EquinoX

  If I have a 32 bit two's complement number and I want to know what is the easiest way to know of two numbers are equal... what would be the fastest bitwise operator to know this? I know xor'ing both numbers and check if the results are zero works well... any other one's? how about if a number is greater than 0?? I can check the 31'st bit to see if it's greater or equal to 0..but how about bgtz?

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• How to find the real problem line in my code with Application Verifier ?

  - by Newbie

  I am now trying to use this Application Verifier debugging tool, but i am stuck, first of all: it breaks the program at a line that is simple variable set line (s = 1; for example) Secondly, now when i run this program under debugger, my program seems to have changed its behaviour: i am drawing image, and now one of the colors has changed o_O, all those parts of the image that i dont draw on, has changed the color to #CDCDCD when it should be #000000, and i already set the default color to zero, still it becomes to #CDCDCD. How do i make any sense to this? Here is the output AV gave me: VERIFIER STOP 00000002: pid 0x8C0: Access violation exception. 14873000 : Invalid address causing the exception 004E422C : Code address executing the invalid access 0012EB08 : Exception record 0012EB24 : Context record AVRF: Noncontinuable verifier stop 00000002 encountered. Terminating process ... The program '[2240] test.exe: Native' has exited with code -1073741823 (0xc0000001).

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• List.clear() followed by List.add() not working.

  - by Vincent

  I have the following C# Class/Function: class Hand { private List<Card> myCards = new List<Card>(); public void sortBySuitValue() { IEnumerable<Card> query = from s in myCards orderby (int)s.suit, (int)s.value select s; myCards = new List<Card>(); myCards.AddRange(query); } } On a card Game. This works fine, however, I had trouble at first, instead of using myCards = new List(); to 'reset' myCards, I would use myCards.clear(), however, once I called the clear function, I would not be able to call myCards.add() or myCards.addRange(). The count would stay at zero. Is my current approach good? Is using LINQ to sort my cards good/bad?

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• WndProc to detect device unplug and plug

  - by Kev Fixx

  How can I know a devices is plug or unplug in WPF? I am using the code below to detect device changes: private void OnSourceInitialized(object sender, EventArgs e) { IntPtr windowHandle = (new WindowInteropHelper(this)).Handle; HwndSource src = HwndSource.FromHwnd(windowHandle); src.AddHook(new HwndSourceHook(WndProc)); } private IntPtr WndProc(IntPtr hwnd, int msg, IntPtr wParam, IntPtr lParam, ref bool handled) { // Handle WM_DEVICECHANGE... if (msg == 0x219) { InitHead(); } return IntPtr.Zero; } Thank you. EDITED: I did the below, still not working: if (msg == 0x0219) { switch (wParam.ToInt32()) { case 0x8000: { InitHead(); } break; } }

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• Faster way of initializing arrays in Delphi

  - by Max

  I'm trying to squeeze every bit of performance in my Delphi application and now I came to a procedure which works with dynamic arrays. The slowest line in it is SetLength(Result, Len); which is used to initialize the dynamic array. When I look at the code for the SetLength procedure I see that it is far from optimal. The call sequence is as follows: _DynArraySetLength - DynArraySetLength DynArraySetLength gets the array length (which is zero for initialization) and then uses ReallocMem which is also unnecessary for initilization. I was doing SetLength to initialize dynamic array all the time. Maybe I'm missing something? Is there a faster way to do this?

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• Fill data gaps without UNION

  - by Dave Jarvis

  Problem There are data gaps that need to be filled, possibly using PARTITION BY. Query Statement The select statement reads as follows: SELECT count( r.incident_id ) AS incident_tally, r.severity_cd, r.incident_typ_cd FROM report_vw r GROUP BY r.severity_cd, r.incident_typ_cd ORDER BY r.severity_cd, r.incident_typ_cd Code Tables The severity codes and incident type codes are from: severity_vw incident_type_vw Actual Result Data 36 0 ENVIRONMENT 1 1 DISASTER 27 1 ENVIRONMENT 4 2 SAFETY 1 3 SAFETY Required Result Data 36 0 ENVIRONMENT 0 0 DISASTER 0 0 SAFETY 27 1 ENVIRONMENT 0 1 DISASTER 0 1 SAFETY 0 2 ENVIRONMENT 0 2 DISASTER 4 2 SAFETY 0 3 ENVIRONMENT 0 3 DISASTER 1 3 SAFETY Any ideas how to use PARTITION BY (or JOINs) to fill in the zero counts?

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• Looking for another regex explanation

  - by Sam

  In my regex expression, I was trying to match a password between 8 and 16 character, with at least 2 of each of the following: lowercase letters, capital letters, and digits. In my expression I have: ^((?=.*\d)(?=.*[a-z])(?=.*[A-Z])(?=.*\d)(?=.*[a-z])(?=.*[A-Z]).{8,16})$ But I don't understand why it wouldn't work like this: ^((?=\d)(?=[a-z])(?=[A-Z])(?=\d)(?=[a-z])(?=[A-Z]){8,16})$ Doesnt ".*" just meant "zero or more of any character"? So why would I need that if I'm just checking for specific conditions? And why did I need the period before the curly braces defining the limit of the password? And one more thing, I don't understand what it means to "not consume any of the string" in reference to "?=".

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• phablet-flash aborting while installing Ubuntu Touch on Nexus 4

  - by Till B

  I have a Nexus 4 with Android 4.3 installed and I want to flash it to Ubuntu Touch. My system is Ubuntu 12.04, running inside a virtual machine on Mac OS 10.5.8. To use the VM, I opened an NAT bridge and forwarded port 5037 for adb, I can see the Nexus with adb and e.g. use the adb shell into it. USB ports are also forwarded to the VM. I follow these instructions to the letter. My bootloader is unlocked, just as it was described in the instructions. Now I encounter different issues, when executing sudo phablet-flash ubuntu-system --no-backup. On the first run, it got stuck in this state: INFO:phablet-flash:Decompressing partitions/recovery.img from /home/till/Downloads/phablet-flash/imageupdates/pool/device-5ba3031cb0d6fc624848266edba781e3e821b6e1e8dd21105725f0ab26077d0a.tar.xz INFO:phablet-flash:Restarting device... wait INFO:phablet-flash:Restarting device... wait complete INFO:phablet-flash:Booting /tmp/tmpMSN8bm/partitions/recovery.img < waiting for device > downloading 'boot.img'... OKAY [ 1.772s] booting... OKAY [ 0.005s] finished. total time: 1.779s INFO:phablet-flash:Waiting for recovery image to boot The following happened: around the line "INFO:phablet-flash: Restarting...", it rebooted into the bootloader. The bootloader shows only for two seconds, then the screen goes off and the phone stays off. But I do notice, that the screen is not off - it is just black, but the background light is on. If I wait long enough, phablet-flash aborts with ERROR:phablet-flash:Wait for recovery expired On the second try, I wanted to manually start the bootloader and choose "Recovery mode". Pressing "volume down+power" at first did nothing. Releasing the buttons and then pressing them again brought me into the bootloder. After choosing "Recovery mode", phablet-flash continued and after a while aborted with the following output: INFO:phablet-flash:Wait for recovery image to boot complete INFO:phablet-flash:Clearing /data and /cache INFO:phablet-flash:Pushing /home/till/Downloads/phablet-flash/imageupdates/pool/ubuntu-2b5345658b58e55207c4a4e7b6b3d8cd4f3d9a3187d2448fc9020c884234bac0.tar.xz to /cache/recovery/ failed to copy '/home/till/Downloads/phablet-flash/imageupdates/pool/ubuntu-2b5345658b58e55207c4a4e7b6b3d8cd4f3d9a3187d2448fc9020c884234bac0.tar.xz' to '/cache/recovery/': Permission denied ERROR:phablet-flash:Command 'adb push /home/till/Downloads/phablet-flash/imageupdates/pool/ubuntu-2b5345658b58e55207c4a4e7b6b3d8cd4f3d9a3187d2448fc9020c884234bac0.tar.xz /cache/recovery/' returned non-zero exit status 1 Removing directory /tmp/tmpDnbz6N Removing directory /tmp/tmpth4L6w What can I do to properly flash my phone with Ubuntu Touch? I noticed that adb does not show the phone in recovery mode: Typing adb devices, when the Nexus 4 is in recovery mode, shows the serial number and the state device, where it should show recovery. Should the phone be rooted? This is not mentioned in the instructions.

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• Java Spotlight Episode 139: Mark Heckler and José Pereda on JES based Energy Monitoring @MkHeck @JPeredaDnr

  - by Roger Brinkley

  Interview with Mark Heckler and José Pereda on using JavaSE Embedded with the Java Embedded Suite on a RaspberryPI along with a JavaFX client to monitor an energy production system and their JavaOne Tutorial- Java Embedded EXTREME MASHUPS: Building self-powering sensor nets for the IoT Right-click or Control-click to download this MP3 file. You can also subscribe to the Java Spotlight Podcast Feed to get the latest podcast automatically. If you use iTunes you can open iTunes and subscribe with this link: Java Spotlight Podcast in iTunes. Show Notes News Java Virtual Developer Day Session Videos Available JavaFX Maven Plugin 2.0 Released JavaFX Scene Builder 1.1 build b28 FXForm 2 release 0.2.2 OpenJDK8/Zero cross compile build for Foundation model HSAIL-based GPU offload: the Quest for Java Performance Begins Progress on Moving to Gradle Java EE 7 Launch Keynote Replay Java EE 7 Technical Breakouts Replay Java EE 7 support in NetBeans 7.3.1 Java EE 7 support in Eclipse 4.3 Java Magazine - May/June Events Jul 16-19, Uberconf, Denver, USA Jul 22-24, JavaOne Shanghai, China Jul 29-31, JVM Language Summit, Santa Clara Sep 11-12, JavaZone, Oslo, Norway Sep 19-20, Strange Loop, St. Louis Sep 22-26 JavaOne San Francisco 2013, USA Feature Interview Mark Heckler is an Oracle Corporation Java/Middleware/Core Tech Engineer with development experience in numerous environments. He has worked for and with key players in the manufacturing, emerging markets, retail, medical, telecom, and financial industries to develop and deliver critical capabilities on time and on budget. Currently, he works primarily with large government customers using Java throughout the stack and across the enterprise. He also participates in open-source development at every opportunity, being a JFXtras project committer and developer of DialogFX, MonologFX, and various other projects. When Mark isn't working with Java, he enjoys writing about his experiences at the Java Jungle website (https://blogs.oracle.com/javajungle/) and on Twitter (@MkHeck). José Pereda is a Structural Engineer working in the School of Engineers in the University of Valladolid in Spain for more than 15 years, and his passion is related to applying programming to solve real problems. Being involved with Java since 1999, José shares his time between JavaFX and the Embedded world, developing commercial applications and open source projects (https://github.com/jperedadnr), and blogging (http://jperedadnr.blogspot.com.es/) or tweeting (@JPeredaDnr) of both. What’s Cool AquaFX 0.1 - Mac OS X skin for JavaFX by Claudine Zillmann DromblerFX adds a docking framework Part 2 of Gerrit’s taming the Nashorn for writing JavaFX apps in Javascript Tool from mihosoft called JSelect for quickly switching JDKs Apache Maven Javadoc Plugin 2.9.1 Released Proposal: Java Concurrency Stress tests (jcstress) Slide-free Code-driven session at SV JUG JavaOne approvals/rejects gone out

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• Retrieving only the first record or record at a certain index in LINQ

  - by vik20000in

  While working with data it’s not always required that we fetch all the records. Many a times we only need to fetch the first record, or some records in some index, in the record set. With LINQ we can get the desired record very easily with the help of the provided element operators. Simple get the first record. If you want only the first record in record set we can use the first method [Note that this can also be done easily done with the help of the take method by providing the value as one].     List<Product> products = GetProductList();      Product product12 = (         from prod in products         where prod.ProductID == 12         select prod)         .First();   We can also very easily put some condition on which first record to be fetched.     string[] strings = { "zero", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine" };     string startsWithO = strings.First(s => s[0] == 'o');  In the above example the result would be “one” because that is the first record starting with “o”.  Also the fact that there will be chances that there are no value returned in the result set. When we know such possibilities we can use the FirstorDefault() method to return the first record or incase there are no records get the default value.        int[] numbers = {};     int firstNumOrDefault = numbers.FirstOrDefault();  In case we do not want the first record but the second or the third or any other later record then we can use the ElementAt() method. In the ElementAt() method we need to pass the index number for which we want the record and we will receive the result for that element.      int[] numbers = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };      int fourthLowNum = (         from num in numbers         where num > 5         select num )         .ElementAt(1); Vikram

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• Web application / Domain model integration using JSON capable DTOs [on hold]

  - by g-makulik

  I'm a bit confused about architectural choices for the web-applications/java/python world. For c/c++ world the available (open source) choices to implement web applications is pretty limited to zero, involving java or python the choices explode to a,- hard to sort out -, mess of available 'frameworks' and application approaches. I want to sort out a clean MVC model, where the M stands for a fully blown (POCO, POJO driven) domain model (according M.Fowler's EAA pattern) using a mature OO language (Java,C++) for implementation. The background is: I have a system with certain hardware components (that introduce system immanent active behavior) and a configuration database for system meta and HW-components configuration data (these are even usually self contained, since the HW-components are capable to persist their configuration data anyway). For realization of the configuration/status data exchange protocol with the HW-components we have chosen the Google Protobuf format, which works well for the directly wired communication with these components. This protocol is already used successfully with a Java based GUI application via TCP/IP connection to the main system controlling HW-component. This application has some drawbacks and design flaws for historical reasons. Now we want to develop an abstract model (domain model) for configuration and monitoring those HW-components, that represents a more use case oriented view to the overall system behavior. I have the feeling that a plain Java class model would fit best for this (c++ implementation seems to have too much implementation/integration overhead with viable language-bridge interfaces). Google Protobuf message definitions could still serve well to describe DTO objects used to interact with a domain model API. But integrating Google Protobuf messages client side for e.g. data binding in the current view doesn't seem to be a good choice. I'm thinking about some extra serialization features, e.g. for JSON based data exchange with the views/controllers. Most lightweight solutions seem to involve a python based presentation layer using JSON based data transfer (I'm at least not sure to be fully informed about this). Is there some lightweight (applicable for a limited ARM Linux platform) framework available, supporting such architecture to realize a web-application? UPDATE: According to my recent research and comments of colleagues I've noticed that using Java (and some JVM) might not be the preferable choice for integration with python on a limited linux system as we have (running on ARM9 with hard to discuss memory and MCU costs), but C/C++ modules would do well for this (since this forms the native interface to python extensions, doesn't it?). I can imagine to provide a domain model from an appropriate C/C++ API (though I still think it's more efforts and higher skill requirements for the involved developers to do with these languages). Still I'm searching for a good approach that supports such architecture. I'll appreciate any pointers!

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• Mathematica Programming Language&ndash;An Introduction

  - by JoshReuben

  The Mathematica http://www.wolfram.com/mathematica/ programming model consists of a kernel computation engine (or grid of such engines) and a front-end of notebook instances that communicate with the kernel throughout a session. The programming model of Mathematica is incredibly rich & powerful – besides numeric calculations, it supports symbols (eg Pi, I, E) and control flow logic.   obviously I could use this as a simple calculator: 5 * 10 --> 50 but this language is much more than that!   for example, I could use control flow logic & setup a simple infinite loop: x=1; While [x>0, x=x,x+1] Different brackets have different purposes: square brackets for function arguments:  Cos[x] round brackets for grouping: (1+2)*3 curly brackets for lists: {1,2,3,4} The power of Mathematica (as opposed to say Matlab) is that it gives exact symbolic answers instead of a rounded numeric approximation (unless you request it):   Mathematica lets you define scoped variables (symbols): a=1; b=2; c=a+b --> 5 these variables can contain symbolic values – you can think of these as partially computed functions:   use Clear[x] or Remove[x] to zero or dereference a variable.   To compute a numerical approximation to n significant digits (default n=6), use N[x,n] or the //N prefix: Pi //N -->3.14159 N[Pi,50] --> 3.1415926535897932384626433832795028841971693993751 The kernel uses % to reference the lastcalculation result, %% the 2nd last, %%% the 3rd last etc –> clearer statements: eg instead of: Sqrt[Pi+Sqrt[Sqrt[Pi+Sqrt[Pi]]] do: Sqrt[Pi]; Sqrt[Pi+%]; Sqrt[Pi+%] The help system supports wildcards, so I can search for functions like so: ?Inv* Mathematica supports some very powerful programming constructs and a rich function library that allow you to do things that you would have to write allot of code for in a language like C++.   the Factor function – factorization: Factor[x^3 – 6*x^2 +11x – 6] --> (-3+x) (-2+x) (-1+x)   the Solve function – find the roots of an equation: Solve[x^3 – 2x + 1 == 0] -->   the Expand function – express (1+x)^10 in polynomial form: Expand[(1+x)^10] --> 1+10x+45x^2+120x^3+210x^4+252x^5+210x^6+120x^7+45x^8+10x^9+x^10 the Prime function – what is the 1000th prime? Prime[1000] -->7919 Mathematica also has some powerful graphics capabilities:   the Plot function – plot the graph of y=Sin x in a single period: Plot[Sin[x], {x,0,2*Pi}] you can also plot 3D surfaces of functions using Plot3D function

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• F# &ndash; Immutable List vs a Mutable Collection in Arrays

  - by MarkPearl

  Another day gone by looking into F#. Today I thought I would ramble on about lists and arrays in F#. Coming from a C# background I barely ever use arrays now days in my C# code – why you may ask – because I find lists generally handle most of the business scenario’s that I come across. So it has been an interesting experience with me keep bumping into Array’s & Lists in F# and I wondered why the frequency of coming across arrays was so much more in this language than in C#. Take for instance the code I stumbled across today. let rng = new Random() let shuffle (array : 'a array) = let n = array.Length for x in 1..n do let i = n-x let j = rng.Next(i+1) let tmp = array.[i] array.[i] <- array.[j] array.[j] <- tmp array   Quite simply its purpose is to “shuffle” an array of items. So I thought, why does it have the “a’ array'” explicitly declared? What if I changed it to a list? Well… as I was about to find out there are some subtle differences between array’s & lists in F# that do not exist in C#. Namely, mutability. A list in F# is an ordered, immutable series of elements of the same type, while an array is a fixed-size zero based, mutable collection of consecutive data elements that are all of the same type. For me the keyword is immutable vs mutable collection. That’s why I could not simply swap the ‘a array with ‘a list in my function header because then later on in the code the syntax would not be valid where I “swap” item positions. i.e. array.[i] <- array.[j] would be invalid because if it was a list, it would be immutable and so couldn’t change by its very definition.. So where does that leave me? It’s to early days to say. I don’t know what the balance will be in future code – will I typically always use lists or arrays or even have a balance, but time will tell.

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• mysql completely removing

  - by Dmitry Teplyakov

  I broke my mysql and now I want to completely reinstall it. I tried: $ sudo apt-get install --reinstall mysql-server $ sudo apt-get remove --purge mysql-client mysql-server But always I see popup with proposal to change root password, I change it and got an error that I can change it.. $ sudo apt-get remove --purge mysql-client mysql-server Reading package lists... Done Building dependency tree Reading state information... Done Package mysql-client is not installed, so not removed Package mysql-server is not installed, so not removed The following packages were automatically installed and are no longer required: libmygpo-qt1 libqtscript4-network libqtscript4-gui libtag-extras1 libqtscript4-sql libqtscript4-xml amarok-utils amarok-common libqtscript4-uitools liblastfm0 libloudmouth1-0 libqtscript4-core Use 'apt-get autoremove' to remove them. 0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded. 1 not fully installed or removed. After this operation, 0 B of additional disk space will be used. Setting up mysql-server-5.5 (5.5.28-0ubuntu0.12.04.2) ... 121114 19:04:03 [Note] Plugin 'FEDERATED' is disabled. 121114 19:04:03 InnoDB: The InnoDB memory heap is disabled 121114 19:04:03 InnoDB: Mutexes and rw_locks use GCC atomic builtins 121114 19:04:03 InnoDB: Compressed tables use zlib 1.2.3.4 121114 19:04:03 InnoDB: Initializing buffer pool, size = 128.0M 121114 19:04:03 InnoDB: Completed initialization of buffer pool InnoDB: Error: auto-extending data file ./ibdata1 is of a different size InnoDB: 0 pages (rounded down to MB) than specified in the .cnf file: InnoDB: initial 640 pages, max 0 (relevant if non-zero) pages! 121114 19:04:03 InnoDB: Could not open or create data files. 121114 19:04:03 InnoDB: If you tried to add new data files, and it failed here, 121114 19:04:03 InnoDB: you should now edit innodb_data_file_path in my.cnf back 121114 19:04:03 InnoDB: to what it was, and remove the new ibdata files InnoDB created 121114 19:04:03 InnoDB: in this failed attempt. InnoDB only wrote those files full of 121114 19:04:03 InnoDB: zeros, but did not yet use them in any way. But be careful: do not 121114 19:04:03 InnoDB: remove old data files which contain your precious data! 121114 19:04:03 [ERROR] Plugin 'InnoDB' init function returned error. 121114 19:04:03 [ERROR] Plugin 'InnoDB' registration as a STORAGE ENGINE failed. 121114 19:04:03 [ERROR] Unknown/unsupported storage engine: InnoDB 121114 19:04:03 [ERROR] Aborting 121114 19:04:03 [Note] /usr/sbin/mysqld: Shutdown complete start: Job failed to start invoke-rc.d: initscript mysql, action "start" failed. dpkg: error processing mysql-server-5.5 (--configure): subprocess installed post-installation script returned error exit status 1 Errors were encountered while processing: mysql-server-5.5 E: Sub-process /usr/bin/dpkg returned an error code (1) It is good for me that I have not any important databases, but..

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