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  • cannot override a concrete member without a third member that's overridden by both

    - by huynhjl
    What does the following error message mean? cannot override a concrete member without a third member that's overridden by both (this rule is designed to prevent ``accidental overrides''); I was trying to do stackable trait modifications. It's a little bit after the fact since I already have a hierarchy in place and I'm trying to modify the behavior without having to rewrite a lot of code. I have a base class called AbstractProcessor that defines an abstract method sort of like this: class AbstractProcessor { def onPush(i:Info): Unit } I have a couple existing traits, to implement different onPush behaviors. trait Pass1 { def onPush(i:Info): Unit = { ... } } trait Pass2 { def onPush(i:Info): Unit = { ... } } So that allows me to use new AbstractProcessor with Pass1 or new AbstractProcessor with Pass2. Now I would like to do some processing before and after the onPush call in Pass1 and Pass2 while minimizing code changes to AbstractProcessor and Pass1 and Pass2. I thought of creating a trait that does something like this: trait Custom extends AbstractProcessor { abstract override def onPush(i:Info): Unit = { // do stuff before super.onPush(i) // do stuff after } And using it with new AbstractProcessor with Pass1 with Custom and I got that error message.

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  • Why is Lua considered a game language?

    - by Hoffmann
    I have been learning about Lua in the past month and I'm absolutely in love with the language, but all I see around that is built with lua are games. I mean, the syntax is very simple, there is no fuss, no special meaning characters that makes code look like regex, has all the good things about a script language and integrates so painlessly with other languages like C, Java, etc. The only down-side I saw so far is the prototype based object orientation that some people do not like (or lack of OO built-in). I do not see how ruby or python are better, surely not in performance ( http://shootout.alioth.debian.org/gp4/benchmark.php?test=all&lang=lua&lang2=python ). I was planning on writting a web app using lua with the Kepler framework and Javascript, but the lack of other projects that use lua as a web language makes me feel a bit uneasy since this is my first try with web development. Lua is considered a kids language, most of you on stackoverflow probably only know the language because of the WoW addons. I can't really see why that is... http://lua-users.org/wiki/LuaVersusPython this link provides some insights on Lua against Python, but this is clearly biased.

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  • Do [sprite stopActionByTag: kTag]; working differently for different CCActions ?

    - by srikanth rongali
    //prog 1 -(void)gameLogic:(ccTime)dt { id actionMove = [CCMoveTo actionWithDuration:1.0 position:ccp(windowSize.width/2-400, actualY)]; [actionMove setTag:6]; [self schedule:@selector(update:)]; [hitBullet runAction:actionMove]; } -(void)update:(ccTime)dt { if ( (CGRectIntersectsRect(hitRect, playerRect)) ) { [[[self getActionByTag:6] retain] autorelease]; [hitBullet stopActionByTag: 6]; } } //prog 2 -(void)gameLogic:(ccTime)dt { id actionMove = [CCMoveTo actionWithDuration:1.0 position:ccp(windowSize.width/2-400, actualY)]; id hitBulletAction = [CCSequence actionWithDuration:(intervalforEnemyshoot)]; id hitBulletSeq = [CCSequence actions: hitBulletAction, actionMove, nil]; [hitBulletSeq setTag:5]; [self schedule:@selector(update:)]; [hitBullet runAction:hitBulletSeq]; } -(void)update:(ccTime)dt { if ( (CGRectIntersectsRect(hitRect, playerRect)) ) { [[[self getActionByTag:5] retain] autorelease]; [hitBullet stopActionByTag: 5]; } } While prog1 is working prog2 is not working ? I think the both are same. But why the two stopActions are working differently in two prog1 and prog2 ? I mean the actions are stopped in prog1 but the actions are not stopping in prog2 ? thank You.

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  • Form values in a list item

    - by Tri
    Here is the site mock-up I'm working on for my job: http://dev.arm.gov/~noensie/dqhands/cgi-bin/explorer. I'm still a novice in web developing and I need help with placing form values in a list item to pass on to another page. I'd rather not go in great detail the purpose of this website, but in terms of its basic use, select the parameters in the middle column for a request and add it to the list on the right column by pressing on "add request" button when it appears. After the list have been populated, a user would submit the selected requests, which will direct them to another page based on the requests selected (or added to the list, same thing). That last sentence is where I'm having a problem. Right now, each of request in the list in the right column are <li> elements and I assign them attribute values that needed to be passed on to the next page. I tried inserting a hidden input with same values, but I'm still not sure how to utilize that; I'm not even sure using the hidden input is the correct way. Also the "submit request" button is located outside the <form> block. I was going to utilize javascript and jQuery to enable the button to serialize the values in the <form> block, but I don't know quite how to do that. Go ahead and take a look at my javascript code (index.js) and slay me, or, I mean, my code. It's still pretty elementary and short (~260 lines, that's short right?). I will take any help for this problem (as the matter of fact, if you see any other problems or a better way of implementation of something, go ahead and mention that too); tips, advice, code samples, or whatever else you can contribute, it will be greatly appreciated. Tri

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  • Which JavaScript framework for me?

    - by LeonixSolutions
    This is not to be a subjective question; nor is it intended to start a religious war. Which JavaScript framework for me? Until now, I haven't coded any JS at all (no biggy, it's just another language). I have been set in my ways and eschewed any client-side code, lest the user have JS turned off, or try to "just change this a little, to see what happens" - and then expect me to support it. So, until now it has all been server-side, with PHP and an ODBC compliant database. However, I am beginning to see advantages to client-side input validation and improved graphical experience for users which would help me to produce more professional web-based applications. I am looking for a framework which : doesn't have a steep learning curve is full-featured, although that does not mean that the one with the most features wins (remember the 80/20 rule) is mature an stable (even if still in development) integrates well with common IDEs if possible. I use NetBeans for PHP (and occasionally MS visual studio for C# (I seem to have drifted away from Eclipse)) allows me to develop web sites/apps for mobile devices support for Goggle charts (or other charting) would be a bonus has good AJAX/JSON support, but I imagine that they all do Taking that into consideration, is there a "right" framework for me, or does it not really matter? I looked briefly at JQuery and JQueryGui and liked what I saw, but I really don't have time, owing to deadlines, to try them all out and see which one suits me, much as I know that I ought to.

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  • NSOperation and fwrite (Iphone)

    - by Sridhar
    Hi, I am having problem with this code.Basically I want to execute the fwrite from a timer function asyncronusly. Here is the code block in my Timer function. (This will call by the timer every 0.2 seconds. -(void)timerFunction { WriteFileOperation * operation = [WriteFileOperation writeFileWithBuffer:pFile buffer:readblePixels length:nBytes*15]; [_queue addOperation:operation]; // Here it is waiting to complete the fwrite } The WrtiteFilerOperation is an NSoperation class which it has to write the passing buffer to a file. I added this code in WriteFileOperation's "start" method. (void)start { if (![NSThread isMainThread]) { [self performSelectorOnMainThread:@selector(start) withObject:nil waitUntilDone:NO]; return; } [self willChangeValueForKey:@"isExecuting"]; _isExecuting = YES; [self didChangeValueForKey:@"isExecuting"]; NSLog(@"write bytes %d",fwrite(_buffer, 1, _nBytes, _file)); free(_buffer); [self finish]; } The problem here is , my timerFunction blocked by NSOperation until it writes the buffer into file.(I mean blocked till start method finishes its execution) and the performance seems same as directly placing the fwrite in timerFunction. I want to just return to timerFunction with out waiting from the start method execution to be completed. What I am doing wrong here ? Thanks In Advance Raghu

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  • How can I test that my hash function is good in terms of max-load?

    - by philcolbourn
    I have read through various papers on the 'Balls and Bins' problem and it seems that if a hash function is working right (ie. it is effectively a random distribution) then the following should/must be true if I hash n values into a hash table with n slots (or bins): Probability that a bin is empty, for large n is 1/e. Expected number of empty bins is n/e. Probability that a bin has k collisions is <= 1/k!. Probability that a bin has at least k collisions is <= (e/k)**k. These look easy to check. But the max-load test (the maximum number of collisions with high probability) is usually stated vaguely. Most texts state that the maximum number of collisions in any bin is O( ln(n) / ln(ln(n)) ). Some say it is 3*ln(n) / ln(ln(n)). Other papers mix ln and log - usually without defining them, or state that log is log base e and then use ln elsewhere. Is ln the log to base e or 2 and is this max-load formula right and how big should n be to run a test? This lecture seems to cover it best, but I am no mathematician. http://pages.cs.wisc.edu/~shuchi/courses/787-F07/scribe-notes/lecture07.pdf BTW, with high probability seems to mean 1 - 1/n.

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  • Bash: how to simply parallelize tasks?

    - by NoozNooz42
    I'm writing a tiny script that calls the "PNGOUT" util on a few hundred PNG files. I simply did this: find $BASEDIR -iname "*png" -exec pngout {} \; And then I looked at my CPU monitor and noticed only one of the core was used, which is quite sad. In this day and age of dual, quad, octo and hexa (?) cores desktop, how do I simply parallelize this task with Bash? (it's not the first time I've had such a need, for quite a lot of these utils are mono-threaded... I already had the case with mp3 encoders). Would simply running all the pngout in the background do? How would my find command look like then? (I'm not too sure how to mix find and the '&' character) I if have three hundreds pictures, this would mean swapping between three hundreds processes, which doesn't seem great anyway!? Or should I copy my three hundreds files or so in "nb dirs", where "nb dirs" would be the number of cores, then run concurrently "nb finds"? (which would be close enough) But how would I do this?

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  • Would it be possible to have a UTF-8-like encoding limited to 3 bytes per character?

    - by dan04
    UTF-8 requires 4 bytes to represent characters outside the BMP. That's not bad; it's no worse than UTF-16 or UTF-32. But it's not optimal (in terms of storage space). There are 13 bytes (C0-C1 and F5-FF) that are never used. And multi-byte sequences that are not used such as the ones corresponding to "overlong" encodings. If these had been available to encode characters, then more of them could have been represented by 2-byte or 3-byte sequences (of course, at the expense of making the implementation more complex). Would it be possible to represent all 1,114,112 Unicode code points by a UTF-8-like encoding with at most 3 bytes per character? If not, what is the maximum number of characters such an encoding could represent? By "UTF-8-like", I mean, at minimum: The bytes 0x00-0x7F are reserved for ASCII characters. Byte-oriented find / index functions work correctly. You can't find a false positive by starting in the middle of a character like you can in Shift-JIS.

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  • "Work stealing" vs. "Work shrugging"?

    - by John
    Why is it that I can find lots of information on "work stealing" and nothing on "work shrugging" as a dynamic load-balancing strategy? By "work-shrugging" I mean busy processors pushing excessive work towards less loaded neighbours rather than idle processors pulling work from busy neighbours ("work-stealing"). I think the general scalability should be the same for both strategies. However I believe that it is much more efficient for busy processors to wake idle processors if and when there is definitely work for them to do than having idle processors spinning or waking periodically to speculatively poll all neighbours for possible work. Anyway a quick google didn't show up anything under the heading of "Work Shrugging" or similar so any pointers to prior-art and the jargon for this strategy would be welcome. Clarification/Confession In more detail:- By "Work Shrugging" I actually envisage the work submitting processor (which may or may not be the target processor) being responsible for looking around the immediate locality of the preferred target processor (based on data/code locality) to decide if a near neighbour should be given the new work instead because they don't have as much work to do. I am talking about an atomic read of the immediate (typically 2 to 4) neighbours' estimated q length here. I do not think this is any more coupling than implied by the thieves polling & stealing from their neighbours - just much less often - or rather - only when it makes economic sense to do so. (I am assuming "lock-free, almost wait-free" queue structures in both strategies). Thanks.

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  • why unsigned int 0xFFFFFFFF is equal to int -1?

    - by conejoroy
    perhaps it's a very stupid question but I'm having a hard time figuring this out =) in C or C++ it is said that the maximum number a size_t (an unsigned int data type) can hold is the same as casting -1 to that data type. for example see http://stackoverflow.com/questions/1420982/invalid-value-for-sizet Why?? I'm confused.. I mean, (talking about 32 bit ints) AFAIK the most significant bit holds the sign in a signed data type (that is, bit 0x80000000 to form a negative number). then, 1 is 0x00000001.. 0x7FFFFFFFF is the greatest positive number a int data type can hold. then, AFAIK the binary representation of -1 int should be 0x80000001 (perhaps I'm wrong). why/how this binary value is converted to anything completely different (0xFFFFFFFF) when casting ints to unsigned?? or.. how is it possible to form a binary -1 out of 0xFFFFFFFF? I have no doubt that in C: ((unsigned int)-1) == 0xFFFFFFFF or ((int)0xFFFFFFFF) == -1 is equally true than 1 + 1 == 2, I'm just wondering why. thanks!

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  • Efficient way of calculating average difference of array elements from array average value

    - by Saysmaster
    Is there a way to calculate the average distance of array elements from array average value, by only "visiting" each array element once? (I search for an algorithm) Example: Array : [ 1 , 5 , 4 , 9 , 6 ] Average : ( 1 + 5 + 4 + 9 + 6 ) / 5 = 5 Distance Array : [|1-5|, |5-5|, |4-5|, |9-5|, |6-5|] = [4 , 0 , 1 , 4 , 1 ] Average Distance : ( 4 + 0 + 1 + 4 + 1 ) / 5 = 2 The simple algorithm needs 2 passes. 1st pass) Reads and accumulates values, then divides the result by array length to calculate average value of array elements. 2nd pass) Reads values, accumulates each one's distance from the previously calculated average value, and then divides the result by array length to find the average distance of the elements from the average value of the array. The two passes are identical. It is the classic algorithm of calculating the average of a set of values. The first one takes as input the elements of the array, the second one the distances of each element from the array's average value. Calculating the average can be modified to not accumulate the values, but caclulating the average "on the fly" as we sequentialy read the elements from the array. The formula is: Compute Running Average of Array's elements ------------------------------------------- RA[i] = E[i] {for i == 1} RA[i] = RA[i-1] - RA[i-1]/i + A[i]/i { for i > 1 } Where A[x] is the array's element at position x, RA[x] is the average of the array's elements between position 1 and x (running average). My question is: Is there a similar algorithm, to calculate "on the fly" (as we read the array's elements), the average distance of the elements from the array's mean value? The problem is that, as we read the array's elements, the final average value of the array is not known. Only the running average is known. So calculating differences from the running average will not yield the correct result. I suppose, if such algorithm exists, it probably should have the "ability" to compensate, in a way, on each new element read for the error calculated as far.

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  • Enumerating a string

    - by JamesB
    I have a status which is stored as a string of a set length, either in a file or a database. I'm looking to enumerate the possible status' I have the following type to define the possible status' Type TStatus = (fsNormal = Ord('N'),fsEditedOnScreen = Ord('O'), fsMissing = Ord('M'),fsEstimated = Ord('E'),fsSuspect = Ord('s'), fsSuspectFromOnScreen = Ord('o'),fsSuspectMissing = Ord('m'), fsSuspectEstimated = Ord('e')); Firstly is this really a good idea? or should I have a seperate const array storing the char conversions? That would mean more than one place to update. Now convert a string to a status array I have the following, but how can I check if a char is valid without looping through the enumeration? Function StrToStatus(Value : String):TStatusArray; var i: Integer; begin if Trim(Value) = '' then begin SetLength(Result,0); Exit; end; SetLength(Result,Length(Value)); for i := 1 to Length(Value) do begin Result[i] := TStatus(Value[i]); // I don't think this line is safe. end; end; AFAIK this should be fine for converting back again. Function StatusToStr(Value : TStatusArray):String; var i: Integer; begin for i := 0 to Length(Value) - 1 do Result := Result + Chr(Ord(Value[i])) end; I'm using Delphi 2007

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  • Inside what the TexBox value is posted back? ViewState or post back data?

    - by burak ozdogan
    In one article I was reading on ViewState, I saw a sentence saying that I should not fall into a mistake to believe that the value of a TextBox is stored in ViewState; it is stored in PostBack data. From here what I understand is when I post back a web form, the input controls values are stored in HTTP Request body. Not in the Viewstate. But as far as I know ViewState values are stored in an hidden field called __VIEWSTATE anyway. Then does it mean that __VIEVSTATE value is not posted in HTTP POST Request body as a postback data? Sounds nonesense to me. In another words, basically if I say the ViewState mechanism for such scenerio works like this, am I seeing it right or skipping something: You enter a value on an empty TextBox and submit the page The value of text box is posted back inside POST HTTP Request body. Nothing inside __VIEWSTATE at this point from the TextBox On the server side, the TextBox is created with the default value on OnInit method of the page The TrackChange property of ViewState is set to true. The posted back data of TextBox is loaded. Because it is different than the TextBox defalut value(because the user entered something), the ViewState of this text box is marked as DIRTY. The new value of the textbox is written into __VIEWSTATE hidden field From now on __VIEWSTATE hiddenfeild contains the last given value of the TextBox The page is sent to the user's browser having the __VIEWSTATE hidden field. But this time containing the last value entered by user which will be ready to be rendered Thanks guys! burak ozdogan

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  • GC output clarification

    - by elec
    I'm running a java application with the following settings: -XX:+CMSParallelRemarkEnabled -XX:+UseConcMarkSweepGC -XX:+UseParNewGC -XX:+PrintGCApplicationStoppedTime -XX:+PrintGCApplicationConcurrentTime -XX:+PrintGCDetails -XX:+PrintGCTimeStamps -XX:+PrintGCDateStamps -XX:+PrintHeapAtGC -XX:+PrintTenuringDistribution I'm not sure how to interpret the related gc logs(below). In particular: Heap after GC invocations=31 (full 3): does this mean there were 31 minor GCs, and 3 full GCs ? What triggers the several consecutive lines of Total time for which the application threads were stopped and Application Time ? Is it possible to get the time stamps associated with each of these lines ? GC logs: Total time for which application threads were stopped: 0.0046910 seconds Application time: 0.7946670 seconds Total time for which application threads were stopped: 0.0002900 seconds Application time: 1.0153640 seconds Total time for which application threads were stopped: 0.0002780 seconds Application time: 1.0161890 seconds Total time for which application threads were stopped: 0.0002760 seconds Application time: 1.0145990 seconds Total time for which application threads were stopped: 0.0002950 seconds Application time: 0.9999800 seconds Total time for which application threads were stopped: 0.0002770 seconds Application time: 1.0151640 seconds Total time for which application threads were stopped: 0.0002730 seconds Application time: 0.9996590 seconds Total time for which application threads were stopped: 0.0002880 seconds Application time: 0.9624290 seconds {Heap before GC invocations=30 (full 3): par new generation total 131008K, used 130944K [0x00000000eac00000, 0x00000000f2c00000, 0x00000000f2c00000) eden space 130944K, 100% used [0x00000000eac00000, 0x00000000f2be0000, 0x00000000f2be0000) from space 64K, 0% used [0x00000000f2bf0000, 0x00000000f2bf0000, 0x00000000f2c00000) to space 64K, 0% used [0x00000000f2be0000, 0x00000000f2be0000, 0x00000000f2bf0000) concurrent mark-sweep generation total 131072K, used 48348K [0x00000000f2c00000, 0x00000000fac00000, 0x00000000fac00000) concurrent-mark-sweep perm gen total 30000K, used 19518K [0x00000000fac00000, 0x00000000fc94c000, 0x0000000100000000) 2010-05-11T09:30:13.888+0100: 384.955: [GC 384.955: [ParNew Desired survivor size 32768 bytes, new threshold 0 (max 0) : 130944K-0K(131008K), 0.0052470 secs] 179292K-48549K(262080K), 0.0053030 secs] [Times: user=0.00 sys=0.00, real=0.01 secs] Heap after GC invocations=31 (full 3): par new generation total 131008K, used 0K [0x00000000eac00000, 0x00000000f2c00000, 0x00000000f2c00000) eden space 130944K, 0% used [0x00000000eac00000, 0x00000000eac00000, 0x00000000f2be0000) from space 64K, 0% used [0x00000000f2be0000, 0x00000000f2be0000, 0x00000000f2bf0000) to space 64K, 0% used [0x00000000f2bf0000, 0x00000000f2bf0000, 0x00000000f2c00000) concurrent mark-sweep generation total 131072K, used 48549K [0x00000000f2c00000, 0x00000000fac00000, 0x00000000fac00000) concurrent-mark-sweep perm gen total 30000K, used 19518K [0x00000000fac00000, 0x00000000fc94c000, 0x0000000100000000) } Total time for which application threads were stopped: 0.0056410 seconds Application time: 0.0475220 seconds Total time for which application threads were stopped: 0.0001800 seconds Application time: 1.0174830 seconds Total time for which application threads were stopped: 0.0003820 seconds Application time: 1.0126350 seconds Total time for which application threads were stopped: 0.0002750 seconds Application time: 1.0155910 seconds Total time for which application threads were stopped: 0.0002680 seconds Application time: 1.0155580 seconds Total time for which application threads were stopped: 0.0002880 seconds Application time: 1.0155480 seconds Total time for which application threads were stopped: 0.0002970 seconds Application time: 0.9896810 seconds

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  • Should I go vor Arrays or Objects in PHP in a CouchDB/Ajax app?

    - by karlthorwald
    I find myself converting between array and object all the time in PHP application that uses couchDB and Ajax. Of course I am also converting objects to JSON and back (for sometimes couchdb but mostly Ajax), but this is not so much disturbing my workflow. At the present I have php objects that are returned by the CouchDB modules I use and on the other hand I have the old habbit to return arrays like array("error"="not found","data"=$dataObj) from my functions. This leads to a mixed occurence of real php objects and nested arrays and I cast with (object) or (array) if necessary. The worst thing is that I know more or less by heart what a function returns, but not what type (array or object), so I often run into type errors. My plan is now to always cast arrays to objects before returning from a function. Of course this implies a lot of refactoring. Is this the right way to go? What about the conversion overhead? Other ideas or tips? Edit: Kenaniah's answer suggests I should go the other way, this would mean I'd cast everything to arrays. And for all the Ajax / JSON stuff and also for CouchDB I would use $myarray = json_decode($json_data,$assoc = false) Even more work to change all the CouchDB and Ajax functions but in the end I have better code.

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  • rich suggestions - why input is null? (seam framework)

    - by Cristian Boariu
    Hi, I'm trying to build a rich suggestions and i do not understand WHY the input value is null... I mean, why inputText value is not taken when i enter something. The .xhtml code: <h:inputText value="#{suggestion.input}" id="text"> </h:inputText> <rich:suggestionbox id="suggestionBoxId" for="text" tokens=",[]" suggestionAction="#{suggestion.getSimilarSpacePaths()}" var="result" fetchValue="#{result.path}" first="0" minChars="2" nothingLabel="No similar space paths found" columnClasses="center" > <h:column> <h:outputText value="#{result.path}" style="font-style:italic"/> </h:column> </rich:suggestionbox> and action class: @Name("suggestion") @Scope(ScopeType.CONVERSATION) public class Suggestion { @In protected EntityManager entityManager; private String input; public String getInput() { return input; } public void setInput(final String input) { this.input = input; } public List<Space> getSimilarSpacePaths() { List<Space> suggestionsList = new ArrayList<Space>(); if (!StringUtils.isEmpty(input) && !input.equals("/")) { final Query query = entityManager.createNamedQuery("SpaceByPathLike"); query.setParameter("path", input + '%'); suggestionsList = (List<Space>) query.getResultList(); } return suggestionsList; } } So, input beeing null, suggestionList is always empty... Why input's value is not posted?

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  • Noob question about a statement in a Java program

    - by happysoul
    I am beginner to java and was trying out this code puzzle from the book head first java which I solved as follows and got the output correct :D class DrumKit { boolean topHat=true; boolean snare=true; void playSnare() { System.out.println("bang bang ba-bang"); } void playTopHat() { System.out.println("ding ding da-ding"); } } public class DrumKitTestDriver { public static void main(String[] args) { DrumKit d =new DrumKit(); if(d.snare==true) { d.playSnare(); } d.playTopHat(); } } Output is :: bang bang ba-bang ding ding da-ding Now the problem is that in that code puzzle one code snippet is left that I did not include..it's as follows d.snare=false; Even though I did not write it , I got the output like the book. I am wondering why is there need for us to set it's value as false even when we know the code is gonna run without it too !?? I am wondering what the coder had in mind ..I mean what could be the possible future use and motive behind doing this ? I am sorry if it's a dumb question. I just wanna know why or why not to include that particular statement ? It's not like there's a loop or something that we need to come out of. Why is that statement there ?

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  • what exactly is the danger of an uninitialized pointer in C

    - by akh2103
    I am trying get a handle on C as I work my way thru Jim Trevor's "Cyclone: A safe dialect of C" for a PL class. Trevor and his co-authors are trying to make a safe version of C, so they eliminate uninitialized pointers in their language. Googling around a bit on uninitialized pointers, it seems like un-initialized pointers point to random locations in memory. It seems like this alone makes them unsafe. If you reference an un-itilialized pointer, you jump to an unsafe part of memory. Period. But the way Trevor talks about them seems to imply that it is more complex. He cites the following code, and explains that when the function FrmGetObjectIndex dereferences f, it isn’t accessing a valid pointer, but rather an unpredictable address — whatever was on the stack when the space for f was allocated. What does Trevor mean by "whatever was on the stack when the space for f was allocated"? Are "un-initialized" pointers initialized to random locations in memory by default? Or does their "random" behavior have to do with the memory allocated for these pointers getting filled with strange values (that are then referenced) because of unexpected behavior on the stack. Form *f; switch (event->eType) { case frmOpenEvent: f = FrmGetActiveForm(); ... case ctlSelectEvent: i = FrmGetObjectIndex(f, field); ... }

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  • Use of var keyword in C#

    - by kronoz
    After discussion with colleagues regarding the use of the 'var' keyword in C# 3 I wondered what people's opinions were on the appropriate uses of type inference via var? For example I rather lazily used var in questionable circumstances, e.g.:- foreach(var item in someList) { // ... } // Type of 'item' not clear. var something = someObject.SomeProperty; // Type of 'something' not clear. var something = someMethod(); // Type of 'something' not clear. More legitimate uses of var are as follows:- var l = new List<string>(); // Obvious what l will be. var s = new SomeClass(); // Obvious what s will be. Interestingly LINQ seems to be a bit of a grey area, e.g.:- var results = from r in dataContext.SomeTable select r; // Not *entirely clear* what results will be here. It's clear what results will be in that it will be a type which implements IEnumerable, however it isn't entirely obvious in the same way a var declaring a new object is. It's even worse when it comes to LINQ to objects, e.g.:- var results = from item in someList where item != 3 select item; This is no better than the equivilent foreach(var item in someList) { // ... } equivilent. There is a real concern about type safety here - for example if we were to place the results of that query into an overloaded method that accepted IEnumerable<int> and IEnumerable<double> the caller might inadvertently pass in the wrong type. Edit - var does maintain strong typing but the question is really whether it's dangerous for the type to not be immediately apparent on definition, something which is magnified when overloads mean compiler errors might not be issued when you unintentionally pass the wrong type to a method. Related Question: http://stackoverflow.com/questions/633474/c-do-you-use-var

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  • Find & Replace - using a Regex for this?

    - by Jack W-H
    Hey folks. Regexs make me cry, so, I came here for help. I'm looking for some tips on Find & Replace in Panic's Coda. I know the F&R is pretty advance but I'm just looking for the best way to do this. I'm trying to rewrite a 'template engine' (very basic) I have going on with a webapp I'm coding in PHP (CodeIgniter). Currently I'm calling my template like so: $this->load->view('subviews/template/headerview'); $this->load->view('subviews/template/menuview'); $this->load->view('subviews/template/sidebar'); $this->load->view('The-View-I-Want-To-Load'); // This is the important line $this->load->view('subviews/template/footerview'); However it's inefficient using five lines of code every time I want to load up a different page, in every different controller. So I rewrote it like this: $data['view'] = 'The-View-I-Want-To-Load'; $this->load->view('template',$data); That way if I need to make any major changes to the design it can easily be done from the template.php view file (which contains the header, menu, sidebar views etc. etc.). However I use the previous 5-lines all over the place in many different controllers and functions. So, my question is --- How can I find and replace the old template engine (5 lines of code) for the new one - substituting in the name of the view in the important, unique line for the one in $data['view]? Does that make any sense?! If not I'll try and rephrase! I mean, is there a way of doing this via a Regex or something? Or am I on completely the wrong lines here? Thanks for your help Jack

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  • Development/runtime Licensing mechanism for a C# class library?

    - by Darryl
    I'm developing a .Net class library (a data provider) and I'm starting to think about how I would handle licensing the library to prospective purchasers. By licensing, I mean the mechanics of trying to prevent my library from being used by those who haven't purchased it, not the software license (i.e., Apache, Gnu, etc). I've never dealt with licensing, and in the past, I've always developed apps, not libraries. I don't want to make things difficult for my customers; know it is not possible to make it ironclad. Just some mechanism that gives me decent protection without making the customer jump through hoops or gnash their teeth. I think the mechanism would check for a valid license when the class is being used in development mode, and not in runtime mode (when the customer's software is released to their customers). I think libraries are typically sold per developer, but I'm not sure how that could be accomplished without making the mechanism odious for my customers; maybe that gets left to the honor system. I Googled this and found many approaches. Ideally, I'd like to do something that is generally accepted and common, the "right" way class libraries are licensed, if that exists, rather than making my customers deal with yet another license mechanism. A firm push in the right direction will be greatly appreciated!

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  • Calculating bounding box a certain distance away from a lat/long coordinate in Java

    - by Bryce Thomas
    Given a coordinate (lat, long), I am trying to calculate a square bounding box that is a given distance (e.g. 50km) away from the coordinate. So as input I have lat, long and distance and as output I would like two coordinates; one being the south-west (bottom-left) corner and one being the north-east (top-right) corner. I have seen a couple of answers on here that try to address this question in Python, but I am looking for a Java implementation in particular. Just to be clear, I intend on using the algorithm on Earth only and so I don't need to accommodate a variable radius. It doesn't have to be hugely accurate (+/-20% is fine) and it'll only be used to calculate bounding boxes over small distances (no more than 150km). So I'm happy to sacrifice some accuracy for an efficient algorithm. Any help is much appreciated. Edit: I should have been clearer, I really am after a square, not a circle. I understand that the distance between the center of a square and various points along the square's perimeter is not a constant value like it is with a circle. I guess what I mean is a square where if you draw a line from the center to any one of the four points on the perimeter that results in a line perpendicular to a side of the perimeter, then those 4 lines have the same length.

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  • Using a class within a class?

    - by Josh
    I built myself a MySQL class which I use in all my projects. I'm about to start a project that is heavily based on user accounts and I plan on building my own class for this aswell. The thing is, a lot of the methods in the user class will be MySQL queries and methods from the MySQL class. For example, I have a method in my user class to update someone's password: class user() { function updatePassword($usrName, $newPass) { $con = mysql_connect('db_host', 'db_user', 'db_pass'); $sql = "UPDATE users SET password = '$newPass' WHERE username = '$userName'"; $res = mysql_query($sql, $con); if($res) return true; mysql_close($con); } } (I kind of rushed this so excuse any syntax errors :) ) As you can see that would use MySQL to update a users password, but without using my MySQL class, is this correct? I see no way in which I can use my MySQL class within my users class without it seeming dirty. Do I just use it the normal way like $DB = new DB();? That would mean including my mysql.class.php somewhere too... I'm quite confused about this, so any help would be appreciated, thanks.

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  • Access 2007 file picker, replaces all rows with the same choice.

    - by SqlStruggle
    This code is from an Access 2007 project I've been struggling with. The actual mean part is the part where I should put something like "update only current form" DoCmd.RunSQL "Update Korut Set [PikkuKuva]=('" & varFile & "') ;" Could someone please help me with this?` If I use it now, it updates all the tables with the same file picked. Heres the whole code. ' This requires a reference to the Microsoft Office 11.0 Object Library. Dim fDialog As Office.FileDialog Dim varFile As Variant Dim filePath As String ' Set up the File dialog box. Set fDialog = Application.FileDialog(msoFileDialogFilePicker) With fDialog ' Allow the user to make multiple selections in the dialog box. .AllowMultiSelect = False ' Set the title of the dialog box. .Title = "Valitse Tiedosto" ' Clear out the current filters, and then add your own. .Filters.Clear .Filters.Add "All Files", "*.*" ' user picked at least one file. If the .Show method returns ' False, the user clicked Cancel. If .Show = True Then ' Loop through each file that is selected and then add it to the list box. For Each varFile In .SelectedItems DoCmd.SetWarnings True DoCmd.RunSQL "Update Korut Set [PikkuKuva]=('" & varFile & "') ;" Next Else MsgBox "You clicked Cancel in the file dialog box." End If End With

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