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  • Scan file contents into an array of a structure.

    - by ZaZu
    Hello, I have a structure in my program that contains a particular array. I want to scan a random file with numbers and put the contents into that array. This is my code : ( NOTE : This is a sample from a bigger program, so I need the structure and arrays as declared ) The contents of the file are basically : 5 4 3 2 5 3 4 2 #include<stdio.h> #define first 500 #define sec 500 struct trial{ int f; int r; float what[first][sec]; }; int trialtest(trial *test); main(){ trial test; trialtest(&test); } int trialtest(trial *test){ int z,x,i; FILE *fin; fin=fopen("randomfile.txt","r"); for(i=0;i<5;i++){ fscanf(fin,"%5.2f\t",(*test).what[z][x]); } fclose(fin); return 0; } But the problem is, whenever this I run this code, I get this error : (25) : warning 508 - Data of type 'double' supplied where a pointer is required I tried adding do{ for(i=0;i<5;i++){ q=fscanf(fin,"%5.2f\t",(*test).what[z][x]); } }while(q!=EOF); But that didnt work either, it gives the same error. Does anyone have a solution to this problem ?

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  • Javascript ( jQuery ) Error: SyntaxError: missing ) after argument list

    - by Obmerk Kronen
    I have the simplest function : jQuery(document).ajaxSuccess(function(e, xhr, settings) { var widget_id_base = '099_cf_samurai_widget'; if(settings.data.search('action=save-widget') != -1 && settings.data.search('id_base=' + widget_id_base) != -1) { // alert(\'yay!'\); my_function_chosen_099(); } }); function my_function_chosen_099(){ jQuery(".chzn-select").chosen(); } which works just fine , but When I add the width Parameter like so : function my_function_chosen_k99(){ jQuery(".chzn-select").chosen(width:'95%'); } it gives me an error of: Error: SyntaxError: missing ) after argument list Source File: http://localhost/my-path/js/o99.chosen.init.js?ver=k99 Line: 20, Column: 41 Source Code: jQuery(".chzn-select").chosen(width:"95%"); .............................................| I have tried escaping: jQuery(".chzn-select").chosen(width:\"95%"\); and even double jQuery(".chzn-select").chosen(width:\\"95%"\\); and in my desperation, even jQuery(".chzn-select").chosen( width:"95%" ); I checked and rechecked the closing of brackets , and also tried with single quotes ' - but nothing . There appear to be a lot of similar questions here , but all I saw was escaping problems, ANd I have tried all that I know .. What is wrong here ?? I assume it is not a simple syntax error - or is it ? ( one which I can not find .. )

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  • How can i design a DB where the user can define the fields and types of a detail table in a M-D rela

    - by Simon
    My application has one table called 'events' and each event has approx 30 standard fields, but also user defined fields that could be any name or type, in an 'eventdata' table. Users can define these event data tables, by specifying x number of fields (either text/double/datetime/boolean) and the names of these fields. This 'eventdata' (table) can be different for each 'event'. My current approach is to create a lookup table for the definitions. So if i need to query all 'event' and 'eventdata' per record, i do so in a M-D relaitionship using two queries (i.e. select * from events, then for each record in 'events', select * from 'some table'). Is there a better approach to doing this? I have implemented this so far, but most of my queries require two distinct calls to the DB - i cannot simply join my master 'events' table with different 'eventdata' tables for each record in in 'events'. I guess my main question is: can i join my master table with different detail tables for each record? E.g. SELECT E.*, E.Tablename FROM events E LEFT JOIN 'E.tablename' T ON E._ID = T.ID If not, is there a better way to design my database considering i have no idea on how many user defined fields there may be and what type they will be.

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  • Regex to GENERATE thumbnails!?!?! (but that's crazy!)

    - by CryptoMonkey
    Hello everyone! So here is my situation, and the solution that I've come up with to solve the problem. I have created an application that includes TinyMCE to allow users to create HTML content for publishing. The user can include images in their markup, and drag/resize those images effecting the final Width/Height attributes in the IMG tag. This is all great, the users can include images and resize/relocate them to their desired appearance. But one big problem is that I am now sending a (possibly) much larger image to the client, only to have the browser resize the image into the requested Width/Height attributes. All that bandwidth and lost load time.... So my solution is to pre-process my users markup content, scanning all of the IMG tags and parsing out the Height/Width/Src attributes. Then set each img's SRC tag to a phpThumb request with the parsed Height/Width passed into the thumbnails URL. This will create my reduced size image (optimising bandwidth at the expense of CPU and caching). What do you think about this solution? I've seen other posts where people were using mod_rewrite to do something similar, but I want to effect the content on the page service and not manipulate the image requests as they're being received. .... Any thoughts about this design? I need some help with the fine details as my regex skills need some work, but I'm very short on time and promise to pay my technical knowledge debt soon. To make the regex's easier, I can be sure of some things. Only img tags that need this processing will have an existing width="" height="" attributes (with the double quotes, and lower cased text, but I suppose matching the text case insensitive would be better if TinyMCE changes) So a regex to match only the necessary Img tags, and maybe another three regex's to extract the src, the width, and the height? Thanks everyone.

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  • Making firefox refresh images faster

    - by Earlz
    I have a thing I'm doing where I need a webpage to stream a series of images from the local client computer. I have a very simple run here: http://jsbin.com/idowi/34 The code is extremely simple setTimeout ( "refreshImage()", 100 ); function refreshImage(){ var date = new Date() var ticks = date.getTime() $('#image').attr('src','http://127.0.0.1:2723/signature?'+ticks.toString()); setTimeout ("refreshImage()", 100 ); } Basically I have a signature pad being used on the client machine. We want for the signature to show up in the web page and for them to see themselves signing it within the web page(the pad does not have an LCD to show it to them right there). So I setup a simple local HTTP server which grabs an image of what the current state of the signature pad looks like and it gets sent to the browser. This has no problems in any browser(tested in IE7, 8, and Chrome) but Firefox where it is extremely laggy and jumpy and doesn't keep with the 10 FPS rate. Does anyone have any ideas on how to fix this? I've tried creating very simple double buffering in javascript but that just made things worse. Also for a bit more information it seems that Firefox is executing the javascript at the correct framerate as on the server the requests are coming in at a constant speed. But the images are only refreshed inconsistently ranging from 5 times per second all the way down to 0 times per second(taking 2 seconds to do a refresh) Also I have tried using different image formats all with the same results. The formats I've tried include bitmaps, PNGs, and GIFs (GIFs caused a minor problem in Chrome with flicker though) Could it be possible that Firefox is somehow caching my images causing a slight lag? I send these headers though: Pragma-directive: no-cache Cache-directive: no-cache Cache-control: no-cache Pragma: no-cache Expires: 0

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  • Calculating percent "x/y * 100" always results in 0?

    - by Patrick Beninga
    In my assignment i have to make a simple version of Craps, for some reason the percentage assignments always produce 0 even when both variables are non 0, here is the code. import java.util.Random; Header, note the variables public class Craps { private int die1, die2,myRoll ,myBet,point,myWins,myLosses; private double winPercent,lossPercent; private Random r = new Random(); Just rolls two dies and produces their some. public int roll(){ die1 = r.nextInt(6)+1; die2 = r.nextInt(6)+1; return(die1 + die2); } The Play method, this just loops through the game. public void play(){ myRoll = roll(); point = 0; if(myRoll == 2 ||myRoll == 3 || myRoll == 12){ System.out.println("You lose!"); myLosses++; }else if(myRoll == 7 || myRoll == 11){ System.out.println("You win!"); myWins++; }else{ point = myRoll; do { myRoll = roll(); }while(myRoll != 7 && myRoll != point); if(myRoll == point){ System.out.println("You win!"); myWins++; }else{ System.out.println("You lose!"); myLosses++; } } } This is where the bug is, this is the tester method. public void tester(int howMany){ int i = 0; while(i < howMany){ play(); i++; } bug is right here in these assignments statements winPercent = myWins/i * 100; lossPercent = myLosses/i* 100; System.out.println("program ran "+i+" times "+winPercent+"% wins "+ lossPercent+"% losses with "+myWins+" wins and "+myLosses+" losses"); } }

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  • expected identifier or '(' before '{' token in Flex

    - by user1829177
    I am trying to use Flex to parse 'C' source code. Unfortunately I am getting the error "expected identifier or '(' before '{' token" on lines 1,12,13,14... . Any ideas why? %{ %} digit [0-9] letter [a-zA-Z] number (digit)+ id (letter|_)(letter|digit|_)* integer (int) character (char) comma [,] %% {integer} {return INT;} {character} {return CHAR;} {number} {return NUM;} {id} {return IDENTIFIER;} {comma} {return ',';} [-+*/] {return *yytext;} . {} %% main() { yylex(); } The corresponding flex file is as shown below: %{ #include <ctype.h> #include <stdio.h> #include "myhead.h" #include "mini.l" #define YYSTYPE double # undef fprintf %} %token INT %token CHAR %token IDENTIFIER %token NUM %token ',' %left '+' '-' %left '*' '/' %right UMINUS %% lines:lines expr '\n' {printf("%g\n",$2);} |lines '\n' |D | ; expr :expr '*' expr {$$=$1*$3;} |expr '/' expr {$$=$1/$3;} |expr '+' expr {$$=$1+$3;} |expr '-' expr {$$=$1+$3;} |'(' expr ')' {$$=$2;} |'-' expr %prec UMINUS {$$=-$2;} |IDENTIFIER {} |NUM {} ; T :INT {} |CHAR {} ; L :L ',' IDENTIFIER {} |IDENTIFIER {} ; D :T L {printf("T is %g, L is %g",$1,$2);} ; %% /*void yyerror (char *s) { fprintf (stderr, "%s\n", s); } */ I am compiling the generated code using the command: gcc my_file.c -ly

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  • C++ ulong to class method pointer and back

    - by Simone Margaritelli
    Hi guys, I'm using a hash table (source code by Google Inc) to store some method pointers defined as: typedef Object *(Executor::*expression_delegate_t)( vframe_t *, Node * ); Where obviously "Executor" is the class. The function prototype to insert some value to the hash table is: hash_item_t *ht_insert( hash_table_t *ht, ulong key, ulong data ); So basically i'm doing the insert double casting the method pointer: ht_insert( table, ASSIGN, reinterpret_cast<ulong>( (void *)&Executor::onAssign ) ); Where table is defined as a 'hash_table_t *' inside the declaration of the Executor class, ASSIGN is an unsigned long value, and 'onAssign' is the method I have to map. Now, Executor::onAssign is stored as an unsigned long value, its address in memory I think, and I need to cast back the ulong to a method pointer. But this code: hash_item_t* item = ht_find( table, ASSIGN ); expression_delegate_t delegate = reinterpret_cast < expression_delegate_t > (item->data); Gives me the following compilation error : src/executor.cpp:45: error: invalid cast from type ‘ulong’ to type ‘Object* (Executor::*)(vframe_t*, Node*)’ I'm using GCC v4.4.3 on a x86 GNU/Linux machine. Any hints?

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  • C++ std::vector memory/allocation

    - by aaa
    from a previous question about vector capacity, http://stackoverflow.com/questions/2663170/stdvector-capacity-after-copying, Mr. Bailey said: In current C++ you are guaranteed that no reallocation occurs after a call to reserve until an insertion would take the size beyond the value of the previous call to reserve. Before a call to reserve, or after a call to reserve when the size is between the value of the previous call to reserve and the capacity the implementation is allowed to reallocate early if it so chooses. So, if I understand correctly, in order to assure that no relocation happens until capacity is exceeded, I must do reserve twice? can you please clarify it? I am using vector as a memory stack like this: std::vector<double> memory; memory.reserve(size); memory.insert(memory.end(), matrix.data().begin(), matrix.data().end()); // smaller than size size_t offset = memory.size(); memory.resize(memory.capacity(), 0); I need to guarantee that relocation does not happen in the above. thank you. ps: I would also like to know if there is a better way to manage memory stack in similar manner other than vector

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  • Set registry to control working dir when associating file-type with application

    - by John
    I'm using Inno for an installer, and I want to associate a file type with my app: Root: HKCR; Subkey: ".rpl"; ValueType: string; ValueName: ""; ValueData: "MyReplay"; Flags: uninsdeletevalue; Root: HKCR; Subkey: "MyReplay"; ValueType: string; ValueName: ""; ValueData: "Replay File"; Flags: uninsdeletekey; Root: HKCR; Subkey: "MyReplay\DefaultIcon"; ValueType: string; ValueName: ""; ValueData: "{app}\bin\MyApp.ico,0"; Flags: uninsdeletekey; Root: HKCR; Subkey: "MyReplay\shell\open\command"; ValueType: string; ValueName: ""; ValueData: """{app}\bin\MyApp.exe"" ""%1"""; Flags: uninsdeletekey; Right now, double-clicking a .rpl file launches the app, but the working dir appears to be where the .rpl file is located, so the app crashes as it can't load any data. Is it posible to set the registry to control the start/working dir for file associations as well as the app that is launched? Or does my app itself need to be able to work around this?

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  • (Java) Get value of string loaded into dynamic-type object?

    - by Michael
    I'm very new to Java (~10 days), so my code is probably pretty bad, but here's what I've got: ArgsDataHolder argsData = new ArgsDataHolder(); // a class that holds two // ArrayList's where each element // representing key/value args Class thisArgClass; String thisArgString; Object thisArg; for(int i=2; i< argsString.length; i++) { thisToken = argsString[i]; thisArgClassString = getClassStringFromToken(thisToken).toLowerCase(); System.out.println("thisArgClassString: " + thisArgClassString); thisArgClass = getClassFromClassString(thisArgClassString); // find closing tag; concatenate middle Integer j = new Integer(i+1); thisArgString = getArgValue(argsString, j, "</" + thisArgClassString + ">"); thisArg = thisArgClass.newInstance(); thisArg = thisArgClass.valueOf(thisArgString); argsData.append(thisArg, thisArgClass); } The user basically has to input a set of key/value arguments into the command prompt in this format: <class>value</class>, e.g. <int>62</int>. Using this example, thisArgClass would be equal to Integer.class, thisArgString would be a string that read "62", and thisArg would be an instance of Integer that is equal to 62. I tried thisArg.valueOf(thisArgString), but I guess valueOf(<String>) is only a method of certain subclasses of Object. For whatever reason, I can't seem to be able to cast thisArg to thisArgClass (like so: thisArg = (thisArgClass)thisArgClass.newInstance();, at which point valueOf(<String>) should become accessible. There's got to be a nice, clean way of doing this, but it is beyond my abilities at this point. How can I get the value of the string loaded into a dynamically-typed object (Integer, Long, Float, Double, String, Character, Boolean, etc.)? Or am I just overthinking this, and Java will do the conversion for me? :confused:

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  • calculating change (over a period) for a dated field

    - by morpheous
    I have two tables with the following schema: CREATE TABLE sales_data ( sales_time date NOT NULL, product_id integer NOT NULL, sales_amt double NOT NULL ); CREATE TABLE date_dimension ( id integer NOT NULL, datestamp date NOT NULL, day_part integer NOT NULL, week_part integer NOT NULL, month_part integer NOT NULL, qtr_part integer NOT NULL, year_part integer NOT NULL, ); I want to write two types of queries that will allow me to calculate: period on period change (e.g. week on week change) change in period on period change (e.g. change in week on week change) I would prefer to write this in ANSI SQL, since I dont want to be tied to any particular db. [Edit] In light of some of the comments, if I have to be tied to a single database (in terms of SQL dialect), it will have to be PostgreSQL The queries I want to write are of the form (pseudo SQL of course): Query Type 1 (Period on Period Change) ======================================= a). select product_id, ((sd2.sales_amt - sd1.sales_amt)/sd1.sales_amt) as week_on_week_change from sales_data sd1, sales_data sd2, date_dimension dd where {SOME CRITERIA) b). select product_id, ((sd2.sales_amt - sd1.sales_amt)/sd1.sales_amt) as month_on_month_change from sales_data sd1, sales_data sd2, date_dimension dd where {SOME CRITERIA) Query Type 2 (Change in Period on Period Change) ================================================= a). select product_id, ((a2.week_on_week_change - a1.week_on_week_change)/a1.week_on_week_change) as change_on_week_on_week_change from (select product_id, ((sd2.sales_amt - sd1.sales_amt)/sd1.sales_amt) as week_on_week_change from sales_data sd1, sales_data sd2, date_dimension dd where {SOME CRITERIA) as a1), (select product_id, ((sd2.sales_amt - sd1.sales_amt)/sd1.sales_amt) as week_on_week_change from sales_data sd1, sales_data sd2, date_dimension dd where {SOME CRITERIA) as a2) WHERE {SOME OTHER CRITERIA}

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  • ReplaceAll not working as expected

    - by Tim Kemp
    Still early days with Mathematica so please forgive what is probably a very obvious question. I am trying to generate some parametric plots. I have: ParametricPlot[{ (a + b) Cos[t] - h Cos[(a + b)/b t], (a + b) Sin[t] - h Sin[(a + b)/b t]}, {t, 0, 2 \[Pi]}, PlotRange -> All] /. {a -> 2, b -> 1, h -> 1} No joy: the replacement rules are not applied and a, b and h remain undefined. If I instead do: Hold@ParametricPlot[{ (a + b) Cos[t] - h Cos[(a + b)/b t], (a + b) Sin[t] - h Sin[(a + b)/b t]}, {t, 0, 2 \[Pi]}, PlotRange -> All] /. {a -> 2, b -> 1, h -> 1} it looks like the rules ARE working, as confirmed by the output: Hold[ParametricPlot[{(2 + 1) Cos[t] - 1 Cos[(2 + 1) t], (2 + 1) Sin[t] - 1 Sin[(2 + 1) t]}, {t, 0, 2 \[Pi]}, PlotRange -> All]] Which is what I'd expect. Take the Hold off, though, and the ParametricPlot doesn't work. There's nothing wrong with the equations or the ParametricPlot itself, though, because I tried setting values for a, b and h in a separate expression (a=2; b=1; h=1) and I get my pretty double cardoid out as expected. So, what am I doing wrong with ReplaceAll and why are the transformation rules not working? This is another fundamentally important aspect of MMA that my OOP-ruined brain isn't understanding. I tried reading up on ReplaceAll and ParametricPlot and the closest clue I found was that "ParametricPlot has attribute HoldAll and evaluates f only after assigning specific numerical values to variables" which didn't help much or I wouldn't be here. Thanks.

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  • C++ CRTP question

    - by aaa
    following piece of code does not compile, the problem is in T::rank not be inaccessible (I think) or uninitialized in parent template. Can you tell me exactly what the problem is? is passing rank explicitly the only way? or is there a way to query tensor class directly? Thank you #include <boost/utility/enable_if.hpp> template<class T, // size_t N, class enable = void> struct tensor_operator; // template<class T, size_t N> template<class T> struct tensor_operator<T, typename boost::enable_if_c< T::rank == 4>::type > { tensor_operator(T &tensor) : tensor_(tensor) {} T& operator()(int i,int j,int k,int l) { return tensor_.layout.element_at(i, j, k, l); } T &tensor_; }; template<size_t N, typename T = double> // struct tensor : tensor_operator<tensor<N,T>, N> { struct tensor : tensor_operator<tensor<N,T> > { static const size_t rank = N; }; I know the workaround, however am interested in mechanics of template instantiation for self-education

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  • Export to csv, string w/ comma in it, splits it up

    - by Brad
    This code exports data into a csv file, which is opened within Excel. When a string has a comma within it, it messes up the order of the data. I need help modifying my code below to resolve any data that contains a comma within it, to not to create a new column. I am assuming it will pass each string within double quotes, so any comma within those quotes, then it will make an exception. Any help is appreciated. $result = mysql_query("select lname, fname, email, dtelephone, etelephone, contactwhen, comments, thursday, friday, saturday, sunday, monday FROM volunteers_2010"); $csv_output .= "Last Name,First Name,Email,Telephone (Day),Telephone (Evening),Contact When,Comments,Thursday,Friday,Saturday,Sunday,Monday,Comments\n"; $i = 0; if (mysql_num_rows($result) > 0) { while ($row = mysql_fetch_assoc($result)) { $csv_output .= $row['Field'].", "; $i++; } } $csv_output .= "\n"; $values = mysql_query("SELECT lname, fname, email, dtelephone, etelephone, contactwhen, comments, thursday, friday, saturday, sunday, monday FROM volunteers_2010 WHERE venue_id = $venue_id"); while ($rowr = mysql_fetch_row($values)) { for ($j=0;$j<$i;$j++) { $csv_output .= $rowr[$j].", "; } $csv_output .= "\n"; }

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  • I just wanted to DES 4096 bytes of data with a 128 bits key...

    - by badp
    ...and what the nice folks at OpenSSL gratiously provide me with is this. :) Now, since you shouldn't be guessing when using cryptography, I come here for confirmation: what is the function call I want to use? What I understood A 128 bits key is 16 byte large, so I'll need double DES (2 × 8 byte). This leaves me with only a few function calls: void DES_ede2_cfb64_encrypt(const unsigned char *in, unsigned char *out, long length, DES_key_schedule *ks1, DES_key_schedule *ks2, DES_cblock *ivec, int *num, int enc); void DES_ede2_cbc_encrypt(const unsigned char *input, unsigned char *output, long length, DES_key_schedule *ks1, DES_key_schedule *ks2, DES_cblock *ivec, int enc); void DES_ede2_cfb64_encrypt(const unsigned char *in, unsigned char *out, long length, DES_key_schedule *ks1, DES_key_schedule *ks2, DES_cblock *ivec, int *num, int enc); void DES_ede2_ofb64_encrypt(const unsigned char *in, unsigned char *out, long length, DES_key_schedule *ks1, DES_key_schedule *ks2, DES_cblock *ivec, int *num); In this case, I guess the function I want to call DES_ede2_cfb64_encrypt, although I'm not so sure -- I definitely don't need padding here and I'd have to care about what ivec and num are, and how I want to generate them... What am I missing?

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  • math.Random isn't working right

    - by RandomlyKnighted
    I'm trying to simulate a coin flip using the code below. public class Coin { public static double result; int[] count = new count[2]; public static void flip() { result = Math.random(); } public static boolean isHeads() { if (result == 0.0) { count[0]++; return false; } else { count[1]++; return true; } } public static void main(String[] args) { flip(); isHeads(); System.out.println(count[0]); System.out.println(count[1]); } } For some reason Eclipse says that the import java.util.Random; is never used even though I'm clearly using it. I didn't put my for loop into the code above but it loops n number of times and then outputs the result. No matter how many times it loops it always returns that the result is greater than 0.0 which can't be right. Am I calling Math.random incorrectly?

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  • write a program that prompts the user to input five decimal numbers

    - by user312309
    This is the question. write a program that prompts the user to input five decimal numbers. the program should then add the five decimal numbers, convert the sum to the nearest integer,m and print the result. This is what I've gotten so far: // p111n9.cpp : Defines the entry point for the console application. // #include <iostream> using namespace std; double a, b , c , d , e, f; int main(int argc, char* argv[]) { cout << "enter 5 decimals: " << endl; cin >> a >> b >> c >> d >> e; f = a + b + c + d + e; return 0; } Now I just need to convert the sum(f) to the nearest integer, m and print the result. How do I do this?

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  • Image on mouseover takes space on PageLoad.

    - by Ram
    Hello, I am trying to show an image on Mouseover and hide it on Mouseout. I am successful in mouseover and mouseout but the image is actually taking the space around the text though i have visibility as hidden.. The text is surrounded with the space of image but the image is displayed on mouseover. Here is the code: <td valign="middle" class="table_td td top" style="width: 347px"> <div id="Style16" style="position:relative; height:100%; left:50%; bottom:700%; visibility:hidden; border:solid 0px #CCC; padding:5px"><img src="images/window-decal-image.gif"></div> <span class="feature_text" style="cursor:pointer" onmouseover="ShowPicture('Style16',1)" onmouseout="ShowPicture('Style16',0)" id="a16">Storefront Window Decal</span> <span class="feature_text_small">(5"x3.5" double sided decal)</span></td> <script language="javascript" type="text/javascript"> function ShowPicture(id,Source) { var vis, elem; if (1 == Source) { vis = "visible"; } else if (0 == Source) { vis = "hidden"; } else { throw new RangeError("Unknown Flag"); } if (elem = document.getElementById(id)) { elem.style.visibility = vis; } else { throw new TypeError("Element with id '"+id+"' does not exist."); } return vis; } </script>

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  • Testing for a closed socket

    - by Robert S. Barnes
    I'm trying to test for a closed socket that has been gracefully closed by the peer without incurring the latency hit of a double send to induce a SIGPIPE. One of the assumptions here is that the socket if closed was gracefully closed by the peer immediately after it's last write / send. Actual errors like a premature close are dealt with else where in the code. If the socket is still open, there will be 0 or more bytes data which I don't actually want to pull out of the socket buffer yet. I was thinking that I could call int ret = recv(sockfd, buf, 1, MSG_DONTWAIT | MSG_PEEK); to determine if the socket is still connected. If it's connected but there's no data in the buffer I'll get a return of -1 with errno == EAGAIN and return the sockfd for reuse. If it's been gracefully closed by the peer I'll get ret == 0 and open a new connection. I've tested this and it seems to work. However, I suspect there is a small window between when I recv the last bit of my data and when the peer FIN arrives in which I could get a false-positive EAGAIN from my test recv. Is this going to bite me, or is there a better way of doing this?

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  • Ruby on Rails: has_many through frustrations

    - by Joe Cairns
    I'm having a frustrating problem with a has_many through: namely the fact that the through models are not created until save. Unfortunately, I need to set data on these models prior to saving the parent. Here's the loose setup: class Wtf < ActiveRecord::Base belongs_to :foo belongs_to :bar end class Bar < ActiveRecord::Base has_many :wtfs has_many :foos, :through => :wtfs end class Foo < ActiveRecord::Base has_many :wtfs has_many :bars, :through => :wtfs def after_initialize Bar.all.each do |bar| bars << bar end end end Everything is fine except that I need to access the "wtf"'s prior to save: f = Foo.new = # f.bars = [list of bars] empty list here f.wtfs = [] f.save! = true now I get stuff f.wtfs = [list of stuff] I even went so far as to explicitly create the wtfs doing this: def after_initialize Bar.all.each do |bar| wtfs << Wtf.new( :foo => self, :bar => bar, :data_i_need_to_set => 10) end end This causes the f.wtfs to be populated, but not the bars. When I save and retrieve, I get double the expected wtfs. Anyone have any ideas?

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  • C++ Type error with Object versus Object reference

    - by muddybruin
    I have the following function (which worked in Visual Studio): bool Plane::contains(Vector& point){ return normalVector.dotProduct(point - position) < -doubleResolution; } When I compile it using g++ version 4.1.2 , I get the following error: Plane.cpp: In member function âvirtual bool Plane::contains(Vector&)â: Plane.cpp:36: error: no matching function for call to âVector::dotProduct(Vector)â Vector.h:19: note: candidates are: double Vector::dotProduct(Vector&) So as you can see, the compiler thinks (point-position) is a Vector but it's expecting Vector&. What's the best way to fix this? I verified that this works: Vector temp = point-position; return normalVector.dotProduct(temp) < -doubleResolution; But I was hoping for something a little bit cleaner. I heard a suggestion that adding a copy constructor might help. So I added a copy constructor to Vector (see below), but it didn't help. Vector.h: Vector(const Vector& other); Vector.cpp: Vector::Vector(const Vector& other) :x(other.x), y(other.y), z(other.z), homogenous(other.homogenous) { }

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  • Value types of variable size

    - by YellPika
    I'm trying to code a small math library in C#. I wanted to create a generic vector structure where the user could define the element type (int, long, float, double, etc.) and dimensions. My first attempt was something like this... public struct Vector<T> { public readonly int Dimensions; public readonly T[] Elements; // etc... } Unfortunately, Elements, being an array, is also a reference type. Thus, doing this, Vector<int> a = ...; Vector<int> b = a; a[0] = 1; b[0] = 2; would result in both a[0] and b[0] equaling 2. My second attempt was to define an interface IVector<T>, and then use Reflection.Emit to automatically generate the appropriate type at runtime. The resulting classes would look roughly like this: public struct Int32Vector3 : IVector<T> { public int Element0; public int Element1; public int Element2; public int Dimensions { get { return 3; } } // etc... } This seemed fine until I found out that interfaces seem to act like references to the underlying object. If I passed an IVector to a function, and changes to the elements in the function would be reflected in the original vector. What I think is my problem here is that I need to be able to create classes that have a user specified number of fields. I can't use arrays, and I can't use inheritance. Does anyone have a solution? EDIT: This library is going to be used in performance critical situations, so reference types are not an option.

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  • an error "has no member named"

    - by helloWorld
    I have this snippet of the code account.cpp #include "account.h" #include <iostream> #include <string> using namespace std; Account::Account(string firstName, string lastName, int id) : strFirstName(firstName), strLastName(lastName), nID(id) {} void Account::printAccount(){ cout << strFirstName; } account.h #include <string> using std::string; class Account{ private: string strLastName; //Client's last name string strFirstName; //Client's first name int nID; //Client's ID number int nLines; //Number of lines related to account double lastBill; public: Account(string firstName, string lastName, int id); void printAccount(); }; company.h #ifndef CELLULAR_COMPANY_H #define CELLULAR_COMPANY_H #include <string> #include <list> #include <iostream> #include "account.h" using namespace std; class Company { private: list<Account> listOfAccounts; public: void addAccount(string firstName, string lastName, int id) { Account newAccount(firstName, lastName, id); listOfAccounts.push_back(newAccount); } void printAccounts(){ for(list<Account>::iterator i = listOfAccounts.begin(); i != listOfAccounts.end(); ++i){ i.printAccount; //here bug } } }; #endif // CELLULAR_COMPANY_H main.cpp #include "cellularcompany.h" int main(){ Company newCompany; newCompany.addAccount("Pavel", "Nedved", 11111); newCompany.printAccounts(); return 0; } can somebody please explain what does my error mean? thanks in advance (I have it in company.h see comment there) I have bug 'struct std::_List_iterator<Account>' has no member named 'printAccount'

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  • Cannot Display Data from MySQL table

    - by MxmastaMills
    I've got a pretty standard call to a MySQL database and for some reason I can't get the code to work. Here's what I have: $mysqli = mysqli_connect("localhost","username","password"); if (!$mysqli) { die('Could not connect: ' . mysqli_error($mysqli)); } session_start(); $sql = "SELECT * FROM jobs ORDER BY id DESC"; $result = $mysqli->query($sql); $num_rows = mysqli_num_rows($result); Now, first, I know that it is connecting properly because I'm not getting the die method plus I added an else conditional in there previously and it checked out. Then the page displays but I get the errors: Warning: mysqli_num_rows() expects parameter 1 to be mysqli_result, boolean given in blablabla/index.php on line 11 Warning: mysqli_fetch_array() expects parameter 1 to be mysqli_result, boolean given in blablabla/index.php on line 12 I've double-checked my database and there is a table called jobs with a row of "id" (it's the primary row). The thing that confuses me is this is code that I literally copied and pasted from another site I built and for some reason the code doesn't work on this one (I obviously copy and pasted it and then just changed the table name and rows accordingly). I saw the error and tried: $num_rows = $mysqli_result->num_rows; $row_array = $mysqli_result->fetch_array; and that fixed the errors but resulted in no data being passed (because obviously $mysqli_result has no value). I don't know why the error is calling for that (is it a difference in version of MySQL or PHP from the other site)? Can someone help me track down the problem? Thanks so much. Sorry if it's something super simple that I'm overlooking, I've been at it for a while.

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