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  • Parsing large txt files in ruby taking a lot of time?

    - by hershey92
    below is the code to download a txt file from internet approx 9000 lines and populate the database, I have tried a lot but it takes a lot of time more than 7 minutes. I am using win 7 64 bit and ruby 1.9.3. Is there a way to do it faster ?? require 'open-uri' require 'dbi' dbh = DBI.connect("DBI:Mysql:mfmodel:localhost","root","") #file = open('http://www.amfiindia.com/spages/NAV0.txt') file = File.open('test.txt','r') lines = file.lines 2.times { lines.next } curSubType = '' curType = '' curCompName = '' lines.each do |line| line.strip! if line[-1] == ')' curType,curSubType = line.split('(') curSubType.chop! elsif line[-4..-1] == 'Fund' curCompName = line.split(" Mutual Fund")[0] elsif line == '' next else sCode,isin_div,isin_re,sName,nav,rePrice,salePrice,date = line.split(';') sCode = Integer(sCode) sth = dbh.prepare "call mfmodel.populate(?,?,?,?,?,?,?)" sth.execute curCompName,curSubType,curType,sCode,isin_div,isin_re,sName end end dbh.do "commit" dbh.disconnect file.close 106799;-;-;HDFC ARBITRAGE FUND RETAIL PLAN DIVIDEND OPTION;10.352;10.3;10.352;29-Jun-2012 This is the format of data to be inserted in the table. Now there are 8000 such lines and how can I do an insert by combining all that and call the procedure just once. Also, does mysql support arrays and iteration to do such a thing inside the routine. Please give your suggestions.Thanks.

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  • How do I deserialize a namespaced element to an object in .net?

    - by pc1oad1etter
    Given this XML snippet: ... <InSide:setHierarchyUpdates> <automaticUpdateInterval>5</automaticUpdateInterval> <shouldRunAutomaticUpdates>true<shouldRunAutomaticUpdates> </InSide:setHierarchyUpdates> ... I am attempting to serialize this object: Imports System.Xml.Serialization <XmlRoot(ElementName:="setHierarchyUpdates", namespace:="InSide")> _ Public Class HierarchyUpdate <XmlElement(ElementName:="shouldRunAutomaticUpdates")> _ Public shouldRunAutomaticUpdates As Boolean <XmlElement(ElementName:="automaticUpdateInterval")> _ Public automaticUpdateInterval As Integer End Class Like this: Dim hierarchyUpdater As New HierarchyUpdate Dim x As New XmlSerializer(hierarchyUpdater.GetType) Dim objReader As Xml.XmlNodeReader = New Xml.XmlNodeReader(myXMLNode) hierarchyUpdater = x.Deserialize(objReader) However, the object, after deserialization, has values of false and zero. If I switch the objReader to a streamreader and read this in as a file, with none of its parents and no namespaces, it works: <setHierarchyUpdates> <automaticUpdateInterval>5</automaticUpdateInterval> <shouldRunAutomaticUpdates>true<shouldRunAutomaticUpdates> </setHierarchyUpdates> What am I doing wrong? Should I use something other than XMLRoot in the class definition, because, as an XML node, it's not really the root? If so, what? Why are no errors returned when this fails?

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  • Could this be considered a well-written class (am I using OOP correctly)?

    - by Ben Dauphinee
    I have been learning OOP principals on my own for a while, and taken a few cracks at writing classes. What I really need to know now is if I am actually using what I have learned correctly, or if I could improve as far as OOP is concerned. I have chopped a massive portion of code out of a class that I have been working on for a while now, and pasted it here. To all you skilled and knowledgeable programmers here I ask: Am I doing it wrong? class acl extends genericAPI{ // -- Copied from genericAPI class protected final function sanityCheck($what, $check, $vars){ switch($check){ case 'set': if(isset($vars[$what])){return(1);}else{return(0);} break; } } // --------------------------------- protected $db = null; protected $dataQuery = null; public function __construct(Zend_Db_Adapter_Abstract $db, $config = array()){ $this->db = $db; if(!empty($config)){$this->config = $config;} } protected function _buildQuery($selectType = null, $vars = array()){ // Removed switches for simplicity sake $this->dataQuery = $this->db->select( )->from( $this->config['table_users'], array('tf' => '(CASE WHEN count(*) > 0 THEN 1 ELSE 0 END)') )->where( $this->config['uidcol'] . ' = ?', $vars['uid'] ); } protected function _sanityRun_acl($sanitycheck, &$vars){ switch($sanitycheck){ case 'uid_set': if(!$this->sanityCheck('uid', 'set', $vars)){ throw new Exception(ERR_ACL_NOUID); } $vars['uid'] = settype($vars['uid'], 'integer'); break; } } private function user($action = null, $vars = array()){ switch($action){ case 'exists': $this->_sanityRun_acl('uid_set', $vars); $this->_buildQuery('user_exists_idcheck', $vars); return($this->db->fetchOne($this->dataQuery->__toString())); break; } } public function user_exists($uid){ return($this->user('exists', array('uid' => $uid))); } } $return = $acl_test->user_exists(1);

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  • Under what circumstances will an entity be able to lazily load its relationships in JPA

    - by Mowgli
    Assuming a Java EE container is being used with JPA persistence and JTA transaction management where EJB and WAR packages are inside a EAR package. Say an entity with lazy-load relationships has just been returned from a JPQL search, such as the getBoats method below: @Stateless public class BoatFacade implements BoatFacadeRemote, BoatFacadeLocal { @PersistenceContext(unitName = "boats") private EntityManager em; @Override public List<Boat> getBoats(Collection<Integer> boatIDs) { if(boatIDs.isEmpty()) { return Collections.<Boat>emptyList(); } Query query = em.createNamedQuery("getAllBoats"); query.setParameter("boatID", boatIDs); List<Boat> boats = query.getResultList(); return boats; } } The entity: @Entity @NamedQuery( name="getAllBoats", query="Select b from Boat b where b.id in : boatID") public class Boat { @Id private long id; @OneToOne(fetch=FetchType.LAZY) private Gun mainGun; public Gun getMainGun() { return mainGun; } } Where will its lazy-load relationships be loadable (assuming the same stateless request): Same JAR: A method in the same EJB A method in another EJB A method in a POJO in the same EJB JAR Same EAR, but outside EJB JAR: A method in a web tier managed bean. A method in a web tier POJO. Different EAR: A method in a different EAR which receives the entity through RMI. What is it that restricts the scope, for example: the JPA transaction, persistence context or JTA transaction?

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  • C# : Regular Expression

    - by Pramodh
    I'm having a set of row data as follows List<String> l_lstRowData = new List<string> { "Data 1 32:01805043*0FFFFFFF", "Data 3, 20.0e-3", "Data 2, 1.0e-3 172:?:CRC" , "Data 6" }; and two List namely "KeyList" and "ValueList" like List<string> KeyList = new List<string>(); List<string> ValueList = new List<string>(); I need to fill the two List<String> from the data from l_lstRowData using Pattern Matching And here is my Pattern for this String l_strPattern = @"(?<KEY>(Data|data|DATA)\s[0-9]*[,]?[ ][0-9e.-]*)[ \t\r\n]*(?<Value>[0-9A-Za-z:?*!. \t\r\n\-]*)"; Regex CompiledPattern=new Regex(l_strPattern,RegexOptions.IgnoreCase | RegexOptions.IgnorePatternWhitespace); So finally the two Lists will contain KeyList { "Data 1" } { "Data 3, 20.0e-3" } { "Data 2, 1.0e-3" } { "Data 6" } ValueList { "32:01805043*0FFFFFFF" } { "" } { "172:?:CRC" } { "" } Scenerio: The Group KEY in the Pattern Should match "The data followed by an integer value , and the if there exist a comma(,) then the next string i.e a double value The Group Value in the Pattern should match string after the whitespace.In the first string it should match 32:01805043*0FFFFFFF but in the 3rd 172:?:CRC. Here is my sample code for (int i = 0; i < l_lstRowData.Count; i++) { MatchCollection M = CompiledPattern.Matches(l_lstRowData[i], 0); KeyList.Add(M[0].Groups["KEY"].Value); ValueList.Add(M[0].Groups["Value"].Value); } But my Pattern is not working in this situation. Please help me to rewrite my Pattern.

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  • How to check user input for correct formatting

    - by Arcadian
    This is what i've come up with so far private void CheckFormatting() { StringReader objReaderf = new StringReader(txtInput.Text); List<String> formatTextList = new List<String>(); do { formatTextList.Add(objReaderf.ReadLine()); } while (objReaderf.Peek() != -1); objReaderf.Close(); for (int i = 0; i < formatTextList.Count; i++) { } } What it is designed to do is check that the user has entered their information in this format Gxx:xx:xx:xx JGxx where "x" can be any integer. As you can see the user inputs their data into a multi-line textbox. i then take that data and enter it into a list. the next part is where i'm stuck. i create a for loop to go through the list line by line, but i guess i will also need to go through each line character by character. How do i do this? or is there a faster way of doing it? thanks in advance

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  • Extracting a number from a 1-word string

    - by Kyle
    In this program I am trying to make, I have an expression (such as "I=23mm", or "H=4V") and I am trying to extract the 23 (or the 4) out of it, so that I can turn it into an integer. The problem I keep running into is that since the expression I am trying to take the numbers out of is 1 word, I cannot use split() or anything. One example I saw but wouldnt work was - I="I=2.7A" [int(s) for s in I.split() if s.isdigit()] This wouldnt work because it only takes the numbers are are delimited by spaces. If there was a number in the word int078vert, it wouldnt extract it. Also, mine doesnt have spaces to delimit. I tried one that looked like this, re.findall("\d+.\d+", "Amps= 1.4 I") but it didnt work either, because the number that is being passed is not always 2 digits. It could be something like 5, or something like 13.6. What code do I need to write so that if I pass a string, such as I="I=2.4A" or I="A=3V" So that I can extract only the number out of this string? (and do operations on it)? There are no spaces or other constant chars that I can delimit by.

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  • Faster or more memory-efficient solution in Python for this Codejam problem.

    - by jeroen.vangoey
    I tried my hand at this Google Codejam Africa problem (the contest is already finished, I just did it to improve my programming skills). The Problem: You are hosting a party with G guests and notice that there is an odd number of guests! When planning the party you deliberately invited only couples and gave each couple a unique number C on their invitation. You would like to single out whoever came alone by asking all of the guests for their invitation numbers. The Input: The first line of input gives the number of cases, N. N test cases follow. For each test case there will be: One line containing the value G the number of guests. One line containing a space-separated list of G integers. Each integer C indicates the invitation code of a guest. Output For each test case, output one line containing "Case #x: " followed by the number C of the guest who is alone. The Limits: 1 = N = 50 0 < C = 2147483647 Small dataset 3 = G < 100 Large dataset 3 = G < 1000 Sample Input: 3 3 1 2147483647 2147483647 5 3 4 7 4 3 5 2 10 2 10 5 Sample Output: Case #1: 1 Case #2: 7 Case #3: 5 This is the solution that I came up with: with open('A-large-practice.in') as f: lines = f.readlines() with open('A-large-practice.out', 'w') as output: N = int(lines[0]) for testcase, i in enumerate(range(1,2*N,2)): G = int(lines[i]) for guest in range(G): codes = map(int, lines[i+1].split(' ')) alone = (c for c in codes if codes.count(c)==1) output.write("Case #%d: %d\n" % (testcase+1, alone.next())) It runs in 12 seconds on my machine with the large input. Now, my question is, can this solution be improved in Python to run in a shorter time or use less memory? The analysis of the problem gives some pointers on how to do this in Java and C++ but I can't translate those solutions back to Python.

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  • How can I compare the performance of log() and fp division in C++?

    - by Ventzi Zhechev
    Hi, I’m using a log-based class in C++ to store very small floating-point values (as the values otherwise go beyond the scope of double). As I’m performing a large number of multiplications, this has the added benefit of converting the multiplications to sums. However, at a certain point in my algorithm, I need to divide a standard double value by an integer value and than do a *= to a log-based value. I have overloaded the *= operator for my log-based class and the right-hand side value is first converted to a log-based value by running log() and than added to the left-hand side value. Thus the operations actually performed are floating-point division, log() and floating-point summation. My question whether it would be faster to first convert the denominator to a log-based value, which would replace the floating-point division with floating-point subtraction, yielding the following chain of operations: twice log(), floating-point subtraction, floating-point summation. In the end, this boils down to whether floating-point division is faster or slower than log(). I suspect that a common answer would be that this is compiler and architecture dependent, so I’ll say that I use gcc 4.2 from Apple on darwin 10.3.0. Still, I hope to get an answer with a general remark on the speed of these two operators and/or an idea on how to measure the difference myself, as there might be more going on here, e.g. executing the constructors that do the type conversion etc. Cheers!

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  • Problem with reading and writing to binary file in C++

    - by Reem
    I need to make a file that contains "name" which is a string -array of char- and "data" which is array of bytes -array of char in C++- but the first problem I faced is how to separate the "name" from the "data"? newline character could work in this case (assuming that I don't have "\n" in the name) but I could have special characters in the "data" part so there's no way to know when it ends so I'm putting an int value in the file before the data which has the size of the "data"! I tried to do this with code as follow: if((fp = fopen("file.bin","wb")) == NULL) { return false; } char buffer[] = "first data\n"; fwrite( buffer ,1,sizeof(buffer),fp ); int number[1]; number[0]=10; fwrite( number ,1,1, fp ); char data[] = "1234567890"; fwrite( data , 1, number[0], fp ); fclose(fp); but I didn't know if the "int" part was right, so I tried many other codes including this one: char buffer[] = "first data\n"; fwrite( buffer ,1,sizeof(buffer),fp ); int size=10; fwrite( &size ,sizeof size,1, fp ); char data[] = "1234567890"; fwrite( data , 1, number[0], fp ); I see 4 "NULL" characters in the file when I open it instead of seeing an integer. Is that normal? The other problem I'm facing is reading that again from the file! The code I tried to read didn't work at all :( I tried it with "fread" but I'm not sure if I should use "fseek" with it or it just read the other character after it. Forgive me but I'm a beginner :(

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  • C++ and its type system: How to deal with data with multiple types?

    - by sub
    "Introduction" I'm relatively new to C++. I went through all the basic stuff and managed to build 2-3 simple interpreters for my programming languages. The first thing that gave and still gives me a headache: Implementing the type system of my language in C++ Think of that: Ruby, Python, PHP and Co. have a lot of built-in types which obviously are implemented in C. So what I first tried was to make it possible to give a value in my language three possible types: Int, String and Nil. I came up with this: enum ValueType { Int, String, Nil }; class Value { public: ValueType type; int intVal; string stringVal; }; Yeah, wow, I know. It was extremely slow to pass this class around as the string allocator had to be called all the time. Next time I've tried something similar to this: enum ValueType { Int, String, Nil }; extern string stringTable[255]; class Value { public: ValueType type; int index; }; I would store all strings in stringTable and write their position to index. If the type of Value was Int, I just stored the integer in index, it wouldn't make sense at all using an int index to access another int, or? Anyways, the above gave me a headache too. After some time, accessing the string from the table here, referencing it there and copying it over there grew over my head - I lost control. I had to put the interpreter draft down. Now: Okay, so C and C++ are statically typed. How do the main implementations of the languages mentioned above handle the different types in their programs (fixnums, bignums, nums, strings, arrays, resources,...)? What should I do to get maximum speed with many different available types? How do the solutions compare to my simplified versions above?

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  • jQuery .height() property not working

    - by Andrew
    I'm attempting to get the height of an element using jQuery, but am receiving some unexpected results. Here's the code: $(function() { var contentheight = $('#subpage-content-small').height; alert(contentheight); }); Where #subpage-content-small has these CSS properties: #subpage-content-small { width: 400px; float: left; margin: 30px 10px 0 0; padding-bottom: 45px; } What I'm getting as an output for my alert is the following: function (f) { var e = this[0]; if (!e) { return f == null ? null : this; } if (c.isFunction(f)) { return this.each(function (j) {var i = c(this);i[d](f.call(this, j, i[d]()));}); } return "scrollTo" in e && e.document ? e.document.compatMode === "CSS1Compat" && e.document.documentElement["client" + b] || e.document.body["client" + b] : e.nodeType === 9 ? Math.max(e.documentElement["client" + b], e.body["scroll" + b], e.documentElement["scroll" + b], e.body["offset" + b], e.documentElement["offset" + b]) : f === w ? c.css(e, d) : this.css(d, typeof f === "string" ? f : f + "px"); } Any idea why I'm getting this as opposed to an integer of the height? Thanks in advance!

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  • Convert VBA to VBS

    - by dnLL
    I have a little VBA script with some functions that I would like to convert to a single VBS file. Here is an example of what I got: Private Declare Function GetPrivateProfileString Lib "kernel32" Alias "GetPrivateProfileStringA" (ByVal lpApplicationName As String, ByVal lpKeyName As Any, ByVal lpDefault As String, ByVal lpReturnedString As String, ByVal nSize As Long, ByVal lpFileName As String) As Long Private Function ReadIniFileString(ByVal Sect As String, ByVal Keyname As String) As String Dim Worked As Long Dim RetStr As String * 128 Dim StrSize As Long Dim iNoOfCharInIni As Integer Dim sIniString, sProfileString As String iNoOfCharInIni = 0 sIniString = "" If Sect = "" Or Keyname = "" Then MsgBox "Erreur lors de la lecture des paramètres dans " & IniFileName, vbExclamation, "INI" Access.Application.Quit Else sProfileString = "" RetStr = Space(128) StrSize = Len(RetStr) Worked = GetPrivateProfileString(Sect, Keyname, "", RetStr, StrSize, IniFileName) If Worked Then iNoOfCharInIni = Worked sIniString = Left$(RetStr, Worked) End If End If ReadIniFileString = sIniString End Function And then, I need to use this function to put some values in strings. VBS doesn't seem to like any of my var declaration ((Dim) MyVar As MyType). If I'm able to adapt that code to VBS, I should be able to do the rest of my functions too. How can I adapt/convert this to VBS? Thank you.

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  • Indy client receive string

    - by Eszee
    Im writing an Indy chat app, and am wondering if there is a way for the server component to tell the client that there is a string waiting, or even a way for the client to have an "OnExecute" like event. This is what i have now: server: procedure TServer.ServerExecute(AContext: TIdContext); var sResponse: string; I: Integer; list: Tlist; begin List := Server.Contexts.LockList; sResponse:= AContext.Connection.Socket.ReadLn; try for I := 0 to List.Count-1 do begin try TIdContext(List[I]).Connection.IOHandler.WriteLn(sResponse); except end; end; finally Server.Contexts.UnlockList; end; end; Client: procedure TForm1.Button1Click(Sender: TObject); var sMsg : string; begin Client.Socket.WriteLn(edit1.Text); sMsg := Client.Socket.ReadLn; Memo1.Lines.Add(sMsg); end; The problem is when i have 2 or more clients running the messages keep stacking because the button only processes 1 message a time. I'd like a way for the client to wait for messages and when it is triggered it processes those messages, like it does now under the button procedure. I've tried to put the "readln" part under a timer, but that causes some major problems. Im Using Delphi 2010 and Indy 10

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  • I just learned about C++ functions, can i use if statements onto functions?

    - by Sagistic
    What I am confused on is about the isNumPalindrome() function. It returns a boolean value of either true or false. How am I suppose to use that so I can display if its a palindrome or not. For ex. If (isNumPalindrome = true) cout "Your number is a palindrome" else "your number is not a palindrome." #include "stdafx.h" int _tmain(int argc, _TCHAR* argv[]) { return 0; } #include <iostream> #include <cmath> using namespace std; int askNumber(); bool isNumPalindrome(); int num, pwr; int main() { askNumber(); isNumPalindrome(); return 0; } bool isNumPalindrome() { int pwr = 0; if (num < 10) return true; else { while (num / static_cast<int>(pow(10.0, pwr)) >=10) pwr++; while (num >=10) { int tenTopwr = static_cast<int>(pow(10.0, pwr)); if ((num / tenTopwr) != (num% 10)) return false; else { num = num % tenTopwr; num = num / 10; pwr = pwr-2; } } return true; } } int askNumber() { cout << "Enter an integer in order to determine if it is a palindrome: " ; cin >> num; cout << endl; return num; }

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  • switch statemt functioning improperly and giving error when i put break;

    - by nav
    The following is the code i used in a program - over here the month variable is an integer switch(month) { case 1: case 3: case 5: case 7: case 8: case 10: case 12: return 31; break; case 2: return 28; break; case 4: case 6: case 9: case 11: return 30; break; default: System.out.println("Invalid month."); return 0; } surprisingly, when i use the above switch construct.. it gives an error saying.. code unreachable for statements after each break statement Then i removed all the break statements, and the new code looks like this --- switch(month) { case 1: case 3: case 5: case 7: case 8: case 10: case 12: return 31; case 2: return 28; case 4: case 6: case 9: case 11: return 30; default: System.out.println("Invalid month."); return 0; } Now.. after removing the break statements .. the code worked perfectly well.. My question is... in the switch construct.. it is mandatory to use break.. or else the control flow continued.. and all the conditions are tested and executed!! right??? So why in the world is the previous ** syntactically Right** version giving an error.. and the modified syntactically incorrect version running perfectly well.. Any explanation.. anyone!!

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  • How to take a NSString such as, "0+1+2", get the sum of those and create new string. Obj-C

    - by Ace Legend
    Alright. My app has a text field and next to it are two buttons (Plus button and Equals button). When you press the "Plus" button, it takes the text inside of the textField and adds a "+" to it. Code below: - (IBAction)plusButtonPressed:(id)sender { NSString *plusString = @"+"; NSString *inputString = carbsField.text; NSString *outputString = [NSString stringWithFormat:@"%@%@",inputString,plusString]; NSLog(@"%@",outputString); [carbsField setText:outputString]; } I will eventually make that more intelligent so that I can't put two pluses or whatever. Anyway, then I want the equal button to take whatever is in the textField, which should look something like: "23+54+2.2" and get the sum of those values. I believe I know how to take an Integer and make it a String, but I want to verify it: int *value = 56; NSString *string = @"%d",value; Well, if anyone can show me how to do this, I would be very appreciative. Thanks. EDIT At the moment, I have not tried anything. This is because I do not know where to start. I have an idea of what to do, but I do not know how to execute it. I believe I need to get all characters before a "+" convert them into int and then get the sum of some array of those values.

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  • Is False == 0 and True == 1 in Python an implementation detail or guaranteed by the language?

    - by EOL
    Is it guaranteed that False == 0 and True == 1, in Python? For instance, is it in any way guaranteed that the following code will always produce the same results, whatever the version of Python (existing and in the foreseeable future)? 0 == False # True 1 == True # True ['zero', 'one'][False] # is 'zero' Any reference to the official documentation would be much appreciated! Other comments would be appreciated too… :) Edit: As noted in many answers, bool inherits from int. The question can therefore be recast as: "Is this an implementation detail that might change in the future, or does the documentation officially say that programmers can rely on booleans inheriting from integers?". This question is relevant for writing robust code that won't fail because of implementation details! Edit 2: The original question is still open, I believe (even though I accepted what I thought was the closest answer): even though Python 3 officially recognizes booleans as integers, I have not yet seen any official integer values for False and True… It therefore looks to me like it is best to stay clear from the assumption that False==0 and True==1.

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  • Else statement crashes when i enter a letter for a cin << int value

    - by TimothyTech
    Alright, i have a question, i veered away from using strings for selection so now i use an integer.when the user enters a number then the game progresses. if they enter a wrong character it SHOULD give the else statement, however if i enter a letter or character the system goes into an endless loop effect then crashes. is there a way to give the else statement even if the user defies the variable's type. // action variable; int c_action: if (c_action == 1){ // enemy attack and user attack with added effect buffer. /////////////////////////////////////////////////////// u_attack = userAttack(userAtk, weapons); enemyHP = enemyHP - u_attack; cout << " charging at the enemy you do " << u_attack << "damage" << endl; e_attack = enemyAttack(enemyAtk); userHP = userHP - e_attack; cout << "however he lashes back causing you to have " << userHP << "health left " << endl << endl << endl << endl; //end of ATTACK ACTION }else{ cout << "invalid actions" << endl; goto ACTIONS; }

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  • How do I make a lock that allows only ONE thread to read from the resource ?

    - by mare
    I have a file that holds an integer ID value. Currently reading the file is protected with ReaderWriterLockSlim as such: public int GetId() { _fileLock.EnterUpgradeableReadLock(); int id = 0; try { if(!File.Exists(_filePath)) CreateIdentityFile(); FileStream readStream = new FileStream(_filePath, FileMode.Open, FileAccess.Read); StreamReader sr = new StreamReader(readStream); string line = sr.ReadLine(); sr.Close(); readStream.Close(); id = int.Parse(line); return int.Parse(line); } finally { SaveNextId(id); // increment the id _fileLock.ExitUpgradeableReadLock(); } } The problem is that subsequent actions after GetId() might fail. As you can see the GetId() method increments the ID every single time, disregarding what happens after it has issued an ID. The issued ID might be left hanging (as said, exceptions might occur). As the ID is incremented, some IDs might be left unused. So I was thinking of moving the SaveNextId(id) out, remove it (the SaveNextId() actually uses the lock too, except that it's EnterWriteLock). And call it manually from outside after all the required methods have executed. That brings out another problem - multiple threads might enter the GetId() method before the SaveNextId() gets executed and they might all receive the same ID. I don't want any solutions where I have to alter the IDs after the operation, correcting them in any way because that's not nice and might lead to more problems. I need a solution where I can somehow callback into the FileIdentityManager (that's the class that handles these IDs) and let the manager know that it can perform the saving of the next ID and then release the read lock on the file containing the ID. Essentialy I want to replicate the relational databases autoincrement behaviour - if anything goes wrong during row insertion, the ID is not used, it is still available for use but it also never happens that the same ID is issued. Hopefully the question is understandable enough for you to provide some solutions..

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  • Prolog Beginner: How to unify with arithmentic cmparison operators or how to get a set var to range

    - by sixtyfootersdude
    I am new to prolog. I need to write an integer adder that will add numbers between 0-9 to other numbers 0-9 and produce a solution 0-18. This is what I want to do: add(in1, in2, out) :- in1 < 10, in2 < 10, out < 18. I would like to be able to call it like this: To Check if it is a valid addition: ?- add(1,2,3). true ?- add(1,2,4). false With one missing variable: ?- add(X,2,3). 1 ?- add(1,4,X). 5 With multiple missing variables: ?-add(X,Y,Z). % Some output that would make sense. Some examples could be: X=1, Y=1, Z=2 ; X=2, Y=1, Z=3 ...... I realize that this is probably a pretty simplistic question and it is probably very straightforward. However cording to the prolog tutorial I am using: "Unlike unification Arithmetic Comparison Operators operators cannot be used to give values to a variable. The can only be evaluated when every term on each side have been instantiated."

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  • Displaying data from linked tables in netbeans JTable

    - by Darc
    I have been writing in java for a few months now and have just started using netbeans. I have spent all day today trying to work out how to connect to an SQL database and display data from 2 tables (ie display the data from from a select statement with an inner join) in a JTable. I have tried using JPQL with the following statment SELECT j, cust.name FROM Job j JOIN j.jobnumber cust where the job table has a field called customer that references id in the customer table. This throws the exception: Caused by: Exception [TOPLINK-8029] (Oracle TopLink Essentials - 2.0.1 (Build b09d-fcs (12/06/2007))): oracle.toplink.essentials.exceptions.EJBQLException Exception Description: Error compiling the query [SELECT j, cust.name FROM Job j JOIN j.jobnumber cust], line 1, column 11: invalid navigation expression [cust.name], cannot navigate expression [cust] of type [java.lang.Integer] inside a query. at oracle.toplink.essentials.exceptions.EJBQLException.invalidNavigation(EJBQLException.java:430) What am i doing wrong? Can anyone point me to some examples of how to make a linked table java application? I am still in the very early stages of development so a complete change is not out of the question if using a mysql database isnt the best way to go about things thanks

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  • Complexity of subset product

    - by threenplusone
    I have a set of numbers produced using the following formula with integers 0 < x < a. f(x) = f(x-1)^2 % a For example starting at 2 with a = 649. {2, 4, 16, 256, 636, 169, 5, 25, 649, 576, 137, ...} I am after a subset of these numbers that when multiplied together equals 1 mod N. I believe this problem by itself to be NP-complete (based on similaries to Subset-Sum problem). However starting with any integer (x) gives the same solution pattern. Eg. a = 649 {2, 4, 16, 256, 636, 169, 5, 25, 649, 576, 137, ...} = 16 * 5 * 576 = 1 % 649 {3, 9, 81, 71, 498, 86, 257, 500, 135, 53, 213, ...} = 81 * 257 * 53 = 1 % 649 {4, 16, 256, 636, 169, 5, 25, 649, 576, 137, 597, ...} = 256 * 25 * 137 = 1 % 649 I am wondering if this additional fact makes this problem solvable faster? Or if anyone has run into this problem previously or has any advice?

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  • MySQL: optimization of table (indexing, foreign key) with no primary keys

    - by Haradzieniec
    Each member has 0 or more orders. Each order contains at least 1 item. memberid - varchar, not integer - that's OK (please do not mention that's not very good, I can't change it). So, thera 3 tables: members, orders and order_items. Orders and order_items are below: CREATE TABLE `orders` ( `orderid` INT(11) UNSIGNED NOT NULL AUTO_INCREMENT, `memberid` VARCHAR( 20 ), `Time` TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP , `info` VARCHAR( 3200 ) NULL , PRIMARY KEY (orderid) , FOREIGN KEY (memberid) REFERENCES members(memberid) ) ENGINE = InnoDB; CREATE TABLE `order_items` ( `orderid` INT(11) UNSIGNED NOT NULL, `item_number_in_cart` tinyint(1) NOT NULL , --- 5 items in cart= 5 rows `price` DECIMAL (6,2) NOT NULL, FOREIGN KEY (orderid) REFERENCES orders(orderid) ) ENGINE = InnoDB; So, order_items table looks like: orderid - item_number_in_cart - price: ... 1000456 - 1 - 24.99 1000456 - 2 - 39.99 1000456 - 3 - 4.99 1000456 - 4 - 17.97 1000457 - 1 - 20.00 1000458 - 1 - 99.99 1000459 - 1 - 2.99 1000459 - 2 - 69.99 1000460 - 1 - 4.99 ... As you see, order_items table has no primary keys (and I think there is no sense to create an auto_increment id for this table, because once we want to extract data, we always extract it as WHERE orderid='1000456' order by item_number_in_card asc - the whole block, id woudn't be helpful in queries). Once data is inserted into order_items, it's not UPDATEd, just SELECTed. The questions are: I think it's a good idea to put index on item_number_in_cart. Could anybody please confirm that? Is there anything else I have to do with order_items to increase the performance, or that looks pretty good? I could miss something because I'm a newbie. Thank you in advance.

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  • Global State and Singletons Dependency injection

    - by Manu
    this is a problem i face lot of times when i am designing a new app i'll use a sample problem to explain this think i am writing simple game.so i want to hold a list of players. i have few options.. 1.use a static field in some class private static ArrayList<Player> players = new ArrayList<Integer>(); public Player getPlayer(int i){ return players.get(i); } but this a global state 2.or i can use a singleton class PlayerList{ private PlayerList instance; private PlayerList(){...} public PlayerList getInstance() { if(instance==null){ ... } return instance; } } but this is bad because it's a singleton 3.Dependency injection class Game { private PlayerList playerList; public Game(PlayerList list) { this.list = list; } public PlayerList getPlayerList() { return playerList; } } this seems good but it's not, if any object outside Game need to look at PlayerList (which is the usual case) i have to use one of the above methods to make the Game class available globally. so I just add another layer to the problem. didn't actually solve anything. what is the optimum solution ? (currently i use Singleton approach)

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