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• Stupid newbie c++ two-dimensional array problem.

  - by paulson scott

  I've no idea if this is too newbie or generic for stackoverlflow. Apologies if that's the case, I don't intend to waste time. I've just started working through C++ Primer Plus and I've hit a little stump. This is probably super laughable but: for (int year = 0; year < YEARS; year++) { cout << "Year " << year + 1 << ":"; for (int month = 0; month < MONTHS; month++) { absoluteTotal = (yearlyTotal[year][year] += sales[year][month]); } cout << yearlyTotal[year][year] << endl; } cout << "The total number of books sold over a period of " << YEARS << " years is: " << absoluteTotal << endl; I wish to display the total of all 3 years. The rest of the code works fine: input is fine, individual yearly output is fine but I just can't get 3 years added together for one final total. I did have the total working at one point but I didn't have the individual totals working. I messed with it and reversed the situation. I've been messing with it for God knows how long. Any idea guys? Sorry if this isn't the place!

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• Pointing class property to another class with vectors

  - by jmclem

  I've got a simple class, and another class that has a property that points to the first class: #include <iostream> #include <vector> using namespace std; class first{ public: int var1; }; class second{ public: first* classvar; }; Then, i've got a void that's supposed to point "classvar" to the intended iteration of the class "first". void fill(vector<second>& sec, vector<first>& fir){ sec[0].classvar = &fir[0]; } Finally the main(). Create and fill a vector of class "first", create "second" vector, and run the fill function. int main(){ vector<first> a(1); a[0].var1 = 1000; vector<second> b(1); fill(b, a); cout << b[0].classvar.var1 << '\n'; system("PAUSE"); return 0; } This gives me the following error: 1>c:\...\main.cpp(29) : error C2228: left of '.var1' must have class/struct/union 1> type is 'first *' And I can't figure out why it reads the "classvar" as the whole vector instead of just the single instance. Should I do this cout << b[0].classvar[0].var1 << '\n'; it reads perfectly. Can anyone figure out the problem? Thanks in advance

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• BASIC Menu-driven program repeates twice after successful completion of first task.

  - by Zazu

  Hello, Im using Plato3 to write C programs. Im creating a menu-driven program but want to test out the basic concept of getting it to work #include<stdio.h> #include<ctype.h> int function1(); main(){ char s; do{ puts("\n choose the following"); puts("(P)rint\n"); puts("(Q)uit\n"); scanf("%c",&s); s=toupper(s); switch (s){ case 'P' : function1(); break; case 'Q' : return -1; break; } }while (function1()==0); } int function1(){ printf("Hello World"); return 0; } The problem is that once function1() returns the value 0, the whole program is echoed ... why ? Example : Running the program gives this : Hello WorldHellow World choose the following (P)rint (Q)uit Hello World choose the following (P)rint (Q)uit -- Any idea why ? Please help, thanks !!!!

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• How to Object Array to List

  - by Peter Black

  (C#) I have 2 classes. 1 is called Employee. The other is my "main". I am trying to take a list and assign each value in list to an array of Employee object. //Inside "Main" class int counter = NameList.Count; Employee[] employee = new Employee[counter]; for (int i = 0; i <= counter; i++) { employee[i].Name = NameList[i]; employee[i].EmpNumber = EmpNumList[i]; employee[i].DateOfHire = DOHList[i]; employee[i].Salary = SalaryList[i]; employee[i].JobDescription = JobDescList[i]; employee[i].Department = DeptList[i]; } This returns the error: An unhandled exception of type 'System.NullReferenceException' occurred in Pgm4.exe Additional information: Object reference not set to an instance of an object. I think this means that I am not calling the list properly. Any help would be much appreciated. Thank you.

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• Django: Determining if a user has voted or not

  - by TheLizardKing

  I have a long list of links that I spit out using the below code, total votes, submitted by, the usual stuff but I am not 100% on how to determine if the currently logged in user has voted on a link or not. I know how to do this from within my view but do I need to alter my below view code or can I make use of the way templates work to determine it? I have read http://stackoverflow.com/questions/1528583/django-vote-up-down-method but I don't quite understand what's going on ( and don't need any ofjavascriptery). Models (snippet): class Link(models.Model): category = models.ForeignKey(Category, blank=False, default=1) user = models.ForeignKey(User) created = models.DateTimeField(auto_now_add=True) modified = models.DateTimeField(auto_now=True) url = models.URLField(max_length=1024, unique=True, verify_exists=True) name = models.CharField(max_length=512) def __unicode__(self): return u'%s (%s)' % (self.name, self.url) class Vote(models.Model): link = models.ForeignKey(Link) user = models.ForeignKey(User) created = models.DateTimeField(auto_now_add=True) def __unicode__(self): return u'%s vote for %s' % (self.user, self.link) Views (snippet): def hot(request): links = Link.objects.select_related().annotate(votes=Count('vote')).order_by('-created') for link in links: delta_in_hours = (int(datetime.now().strftime("%s")) - int(link.created.strftime("%s"))) / 3600 link.popularity = ((link.votes - 1) / (delta_in_hours + 2)**1.5) if request.user.is_authenticated(): try: link.voted = Vote.objects.get(link=link, user=request.user) except Vote.DoesNotExist: link.voted = None links = sorted(links, key=lambda x: x.popularity, reverse=True) links = paginate(request, links, 15) return direct_to_template( request, template = 'links/link_list.html', extra_context = { 'links': links, }) The above view actually accomplishes what I need but in what I believe to be a horribly inefficient way. This causes the dreaded n+1 queries, as it stands that's 33 queries for a page containing just 29 links while originally I got away with just 4 queries. I would really prefer to do this using Django's ORM or at least .extra(). Any advice?

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• Storing a jpa entity where only the timestamp changes results in updates rather than inserts (desire

  - by David Schlenk

  I have a JPA entity that stores a fk id, a boolean and a timestamp: @Entity public class ChannelInUse implements Serializable { @Id @GeneratedValue private Long id; @ManyToOne @JoinColumn(nullable = false) private Channel channel; private boolean inUse = false; @Temporal(TemporalType.TIMESTAMP) private Date inUseAt = new Date(); ... } I want every new instance of this entity to result in a new row in the table. For whatever reason no matter what I do it always results in the row getting updated with a new timestamp value rather than creating a new row. Even tried to just use a native query to run an insert but channel's ID wasn't populated yet so I gave up on that. I've tried using an embedded id class consisting of channel.getId and inUseAt. My equals and hashcode for are: public boolean equals(Object obj){ if(this == obj) return true; if(!(obj instanceof ChannelInUse)) return false; ChannelInUse ciu = (ChannelInUse) obj; return ( (this.inUseAt == null ? ciu.inUseAt == null : this.inUseAt.equals(ciu.inUseAt)) && (this.inUse == ciu.inUse) && (this.channel == null ? ciu.channel == null : this.channel.equals(ciu.channel)) ); } /** * hashcode generated from at, channel and inUse properties. */ public int hashCode(){ int hash = 1; hash = hash * 31 + (this.inUseAt == null ? 0 : this.inUseAt.hashCode()); hash = hash * 31 + (this.channel == null ? 0 : this.channel.hashCode()); if(inUse) hash = hash * 31 + 1; else hash = hash * 31 + 0; return hash; } } I've tried using hibernate's Entity annotation with mutable=false. I'm probably just not understanding what makes an entity unique or something. Hit the google pretty hard but can't figure this one out.

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• EF4 Code-First CTP5 Many-to-one

  - by Kevin McKelvin

  I've been trying to get EF4 CTP5 to play nice with an existing database, but struggling with some basic mapping issues. I have two model classes so far: public class Job { [Key, Column(Order = 0)] public int JobNumber { get; set; } [Key, Column(Order = 1)] public int VersionNumber { get; set; } public virtual User OwnedBy { get; set; } } and [Table("Usernames")] public class User { [Key] public string Username { get; set; } public string EmailAddress { get; set; } public bool IsAdministrator { get; set; } } And I have my DbContext class exposing those as IDbSet I can query my users, but as soon as I added the OwnedBy field to the Job class I began getting this error in all my tests for the Jobs: Invalid column name 'UserUsername'. I want this to behave like NHibernate's many-to-one, whereas I think EF4 is treating it as a complex type. How should this be done?

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• C++: Reference and Pointer question (example regarding OpenGL)

  - by Jay

  I would like to load textures, and then have them be used by multiple objects. Would this work? class Sprite { GLuint* mTextures; // do I need this to also be a reference? Sprite( GLuint* textures ) // do I need this to also be a reference? { mTextures = textures; } void Draw( textureNumber ) { glBindTexture( GL_TEXTURE_2D, mTextures[ textureNumber ] ); // drawing code } }; // normally these variables would be inputed, but I did this for simplicity. const int NUMBER_OF_TEXTURES = 40; const int WHICH_TEXTURE = 10; void main() { std::vector<GLuint> the_textures; the_textures.resize( NUMBER_OF_TEXTURES ); glGenTextures( NUMBER_OF_TEXTURES, &the_textures[0] ); // texture loading code Sprite the_sprite( &the_textures[0] ); the_sprite.Draw( WHICH_TEXTURE ); } And is there a different way I should do this, even if it would work? Thanks.

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• How to get address of va_arg?

  - by lionbest

  I hack some old C API and i got a compile error with the following code: void OP_Exec( OP* op , ... ) { int i; va_list vl; va_start(vl,op); for( i = 0; i < op->param_count; ++i ) { switch( op->param_type[i] ) { case OP_PCHAR: op->param_buffer[i] = va_arg(vl,char*); // ok it works break; case OP_INT: op->param_buffer[i] = &va_arg(vl,int); // error here break; // ... more here } } op->pexec(op); va_end(vl); } The error with gcc version 4.4.1 (Ubuntu 4.4.1-4ubuntu9) was: main.c|55|error: lvalue required as unary ‘&’ operand So why exactly it's not possible here to get a pointer to argument? How to fix it? This code is executed very often with different OP*, so i prefer to not allocate extra memory. Is it possible to iterate over va_list knowing only the size of arguments?

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• dropdownlist binding from function in code behind aspx vb

  - by Dr.H

  so I have this working in C# , why it is not working in VB public string[] CustomizedRoles() { int length = Roles.GetAllRoles().Length; string[] arrRoles=Roles.GetAllRoles(); string[] customizedRoles= new string[length+1]; customizedRoles[0] = ""; for (int i = 1; i < length+1; i++) { customizedRoles[i] = arrRoles[i-1]; } return customizedRoles; } asp:GridView.... asp:DropDownList ID="ddlOwnerRolesUpdate" runat="server" DataSource="<%# CustomizedRoles() %" Height="25px" Width="177px" SelectedValue='<%# Bind("Owner") %' where is "Owner" is a data value come from a datasource for the grid it is working fine in C# . in Vb with the same aspx and this code behind it is not working. Public Function CustomizedRoles() As String() Dim length As Integer = Roles.GetAllRoles().Length Dim arrRoles As String() = Roles.GetAllRoles() Dim _customizedRoles As String() = New String(length + 1) {} _customizedRoles(0) = " " For index As Integer = 1 To length _customizedRoles(index) = arrRoles(index - 1) Next Return _customizedRoles End Function can anyone show me how to bind array of string to a dropdownlist from aspx to code behind in VB

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• Lucene DuplicateFilter question

  - by chardex

  Hi, Why DuplicateFilter doesn't work together with other filters? For example, if a little remake of the test DuplicateFilterTest, then the impression that the filter is not applied to other filters and first trims results: public void testKeepsLastFilter() throws Throwable { DuplicateFilter df = new DuplicateFilter(KEY_FIELD); df.setKeepMode(DuplicateFilter.KM_USE_LAST_OCCURRENCE); Query q = new ConstantScoreQuery(new ChainedFilter(new Filter[]{ new QueryWrapperFilter(tq), // new QueryWrapperFilter(new TermQuery(new Term("text", "out"))), // works right, it is the last document. new QueryWrapperFilter(new TermQuery(new Term("text", "now"))) // why it doesn't work? It is the third document. }, ChainedFilter.AND)); ScoreDoc[] hits = searcher.search(q, df, 1000).scoreDocs; assertTrue("Filtered searching should have found some matches", hits.length > 0); for (int i = 0; i < hits.length; i++) { Document d = searcher.doc(hits[i].doc); String url = d.get(KEY_FIELD); TermDocs td = reader.termDocs(new Term(KEY_FIELD, url)); int lastDoc = 0; while (td.next()) { lastDoc = td.doc(); } assertEquals("Duplicate urls should return last doc", lastDoc, hits[i].doc); } }

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• Java - Reading a csv file line by line - stuck with weird non-existent characters being read!

  - by rockit

  hello fellow java developers. I'm having a very strange issue. I'm trying to read a csv file line by line. Im at the point where Im just testing out the reading of the lines. ONly each time that I read a line, the line contains square characters between each character of text. I even saved the file as a txt file in wordpad and notepad with no change. Thus I must be doing something stupid... I have a csv file, standard csv file, yes a text file with commas in it. I try to read a line of text, but the text is all f-ed up and cannot find the phrase within the text. Any advice? code below. //open csv File filReadMe = new File(strRoot + "data2.csv"); BufferedReader brReadMe = new BufferedReader(new InputStreamReader(new FileInputStream(filReadMe))); String strLine = brReadMe.readLine(); //for all lines while (strLine != null){ //if line contains "(see also" if (strLine.toLowerCase().contains("(see also")){ //write line from "(see also" to ")" int iBegin = strLine.toLowerCase().indexOf("(see also"); String strTemp = strLine.substring(iBegin); int iLittleEnd = strTemp.indexOf(")"); System.out.println(strLine.substring(iBegin, iBegin + iLittleEnd)); } //update line strLine = brReadMe.readLine(); } //end for brReadMe.close();

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• How do you search a document for a string in c++?

  - by Jeff

  Here's my code so far: #include<iostream> #include<string> #include<fstream> using namespace std; int main() { int count = 0; string fileName; string keyWord; string word; cout << "Please make sure the document is in the same file as the program, thank you!" << endl << "Please input document name: " ; getline(cin, fileName); cout << endl; cout << "Please input the word you'd like to search for: " << endl; cin >> keyWord; cout << endl; ifstream infile(fileName.c_str()); while(infile.is_open()) { getline(cin,word); if(word == keyWord) { cout << word << endl; count++; } if(infile.eof()) { infile.close(); } } cout << count; } I'm not sure how to go to the next word, currently this infinite loops...any recommendation? Also...how do I tell it to print out the line that that word was on? Thanks in advance!

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• ISO C90 forbids mixed declarations and code sscanf

  - by Need4Sleep

  I'm getting a strange error attempting to compile my unit test code,. For some reason the compiler treats my sscanf call as a mixed declaration? I don't quite understand, here is the entire error: cc1: warnings being treated as errors /home/brlcad/brlcad/src/libbn/tests/bn_complex.c: In function 'main': /home/brlcad/brlcad/src/libbn/tests/bn_complex.c:53: error: ISO C90 forbids mixed declarations and code make[2]: *** [src/libbn/tests/CMakeFiles/tester_bn_complex.dir/bn_complex.c.o] Error 1 make[1]: *** [src/libbn/tests/CMakeFiles/tester_bn_complex.dir/all] Error 2 make: *** [all] Error 2 int main(int argc, char *argv[]) { double expRe1, expIm2, expSqRe1, expSqIm2; double actRe1, actIm2, actSqRe1, actSqIm2; actRe1 = actIm2 = actSqRe1 = actSqIm2 = expRe1 = expIm2 = expSqRe1 = expSqIm2 = 0.0; bn_complex_t com1,com2; //a struct that holds two doubles if(argc < 5) bu_exit(1, "ERROR: Invalid parameters[%s]\n", argv[0]); sscanf(argv[1], "%lf,%lf", &com1.re, &com1.im); /* Error is HERE */ sscanf(argv[2], "%lf,%lf", &com2.re, &com2.im); sscanf(argv[3], "%lf,%lf", &expRe1, &expIm2); sscanf(argv[4], "%lf,%lf", &expSqRe1, &expSqIm2); test_div(com1, com2, &actRe1, &actIm2); test_sqrt(com1,com2, &actSqRe1, &actSqIm2); if((fabs(actRe1 - expRe1) < 0.00001) || (fabs(actIm2 - expIm2) < 0.00001)){ printf("Division failed...\n"); return 1; } if((fabs(actSqRe1 - expSqRe1) < 0.00001) || (fabs(actSqIm2 - expSqIm2) < 0.00001)){ printf("Square roots failed...\n"); return 1; } return 0; }

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• problem finding a header with a c++ makefile

  - by Max

  Hi. I've started working with my first makefile. I'm writing a roguelike in C++ using the libtcod library, and have the following hello world program to test if my environment's up and running: #include "libtcod.hpp" int main() { TCODConsole::initRoot(80, 50, "PartyHack"); TCODConsole::root->printCenter(40, 25, TCOD_BKGND_NONE, "Hello World"); TCODConsole::flush(); TCODConsole::waitForKeypress(true); } My project directory structure looks like this: /CppPartyHack ----/libtcod-1.5.1 # this is the libtcod root folder --------/include ------------libtcod.hpp ----/PartyHack --------makefile --------partyhack.cpp # the above code (while we're here, how do I do proper indentation? Using those dashes is silly.) and here's my makefile: SRCDIR = . INCDIR = ../libtcod-1.5.1/include CFLAGS = $(FLAGS) -I$(INCDIR) -I$(SRCDIR) -Wall CC = gcc CPP = g++ .SUFFIXES: .o .h .c .hpp .cpp $(TEMP)/%.o : $(SRCDIR)/%.cpp $(CPP) $(CFLAGS) -o $@ -c $< $(TEMP)/%.o : $(SRCDIR)/%.c $(CC) $(CFLAGS) -o $@ -c $< CPP_OBJS = $(TEMP)partyhack.o all : partyhack partyhack : $(CPP_OBJS) $(CPP) $(CPP_OBJS) -o $@ -L../libtcod-1.5.1 -ltcod -ltcod++ -Wl,-rpath,. clean : \rm -f $(CPP_OBJS) partyhack I'm using Ubuntu, and my terminal gives me the following errors: max@max-desktop:~/Desktop/Development/CppPartyhack/PartyHack$ make g++ -c -o partyhack.o partyhack.cpp partyhack.cpp:1:23: error: libtcod.hpp: No such file or directory partyhack.cpp: In function ‘int main()’: partyhack.cpp:5: error: ‘TCODConsole’ has not been declared partyhack.cpp:6: error: ‘TCODConsole’ has not been declared partyhack.cpp:6: error: ‘TCOD_BKGND_NONE’ was not declared in this scope partyhack.cpp:7: error: ‘TCODConsole’ has not been declared partyhack.cpp:8: error: ‘TCODConsole’ has not been declared make: * [partyhack.o] Error 1 So obviously, the makefile can't find libtcod.hpp. I've double checked and I'm sure the relative path to libtcod.hpp in INCDIR is correct, but as I'm just starting out with makefiles, I'm uncertain what else could be wrong. My makefile is based off a template that the libtcod designers provided along with the library itself, and while I've looked at a few online makefile tutorials, the code in this makefile is a good bit more complicated than any of the examples the tutorials showed, so I'm assuming I screwed up something basic in the conversion. Thanks for any help.

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• Efficiency of manually written loops vs operator overloads (C++)

  - by Sagekilla

  Hi all, in the program I'm working on I have 3-element arrays, which I use as mathematical vectors for all intents and purposes. Through the course of writing my code, I was tempted to just roll my own Vector class with simple +, -, *, /, etc overloads so I can simplify statements like: for (int i = 0; i < 3; i++) r[i] = r1[i] - r2[i]; // becomes: r = r1 - r2; Which should be more or less identical in generated code. But when it comes to more complicated things, could this really impact my performance heavily? One example that I have in my code is this: Manually written version: for (int j = 0; j < 3; j++) { p.vel[j] = p.oldVel[j] + (p.oldAcc[j] + p.acc[j]) * dt2 + (p.oldJerk[j] - p.jerk[j]) * dt12; p.pos[j] = p.oldPos[j] + (p.oldVel[j] + p.vel[j]) * dt2 + (p.oldAcc[j] - p.acc[j]) * dt12; } Using a Vector class with operator overloads: p.vel = p.oldVel + (p.oldAcc + p.acc) * dt2 + (p.oldJerk - p.jerk) * dt12; p.pos = p.oldPos + (p.oldVel + p.vel) * dt2 + (p.oldAcc - p.acc) * dt12; I am compiling my code for maximum possible speed, as it's extremely important that this code runs quickly and calculates accurately. So will me relying on my Vector's for these sorts of things really affect me? For those curious, this is part of some numerical integration code which is not trivial to run in my program. Any insight would be appreciated, as would any idioms or tricks I'm unaware of.

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• Can JMX operations take interfaces as parameters?

  - by Thor84no

  I'm having problems with an MBean that takes a Map<String, Object> as a parameter. If I try to execute it via JMX using a proxy object, I get an Exception: Caused by: javax.management.ReflectionException at org.jboss.mx.server.AbstractMBeanInvoker.invoke(AbstractMBeanInvoker.java:231) at org.jboss.mx.server.MBeanServerImpl.invoke(MBeanServerImpl.java:668) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:597) Caused by: java.lang.IllegalArgumentException: Unable to find operation updateProperties(java.util.HashMap) It appears that it attempts to use the actual implementation class rather than the interface, and doesn't check if this is a child of the required interface. The same thing happens for extended classes (for example declare HashMap, pass in LinkedHashMap). Does this mean it's impossible to use an interface for such methods? At the moment I'm getting around it by changing the method signature to accept a HashMap, but it seems odd that I wouldn't be able to use interfaces (or extended classes) in my MBeans. Edit: The proxy object is being created by an in-house utility class called JmxInvocationHandler. The (hopefully) relevant parts of it are as follows: public class JmxInvocationHandler implements InvocationHandler { ... public static <T> T createMBean(final Class<T> iface, SFSTestProperties properties, String mbean, int shHostID) { T newProxyInstance = (T) Proxy.newProxyInstance(iface.getClassLoader(), new Class[] { iface }, (InvocationHandler) new JmxInvocationHandler(properties, mbean, shHostID)); return newProxyInstance; } ... private JmxInvocationHandler(SFSTestProperties properties, String mbean, int shHostID) { this.mbeanName = mbean + MBEAN_SUFFIX + shHostID; msConfig = new MsConfiguration(properties.getHost(0), properties.getMSAdminPort(), properties.getMSUser(), properties.getMSPassword()); } ... public Object invoke(Object proxy, Method method, Object[] args) throws Throwable { if (management == null) { management = ManagementClientStore.getInstance().getManagementClient(msConfig.getHost(), msConfig.getAdminPort(), msConfig.getUser(), msConfig.getPassword(), false); } final Object result = management.methodCall(mbeanName, method.getName(), args == null? new Object[] {} : args); return result; } }

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• Haskell Cons Operator (:)

  - by Carson Myers

  I am really new to Haskell (Actually I saw "Real World Haskell" from O'Reilly and thought "hmm, I think I'll learn functional programming" yesterday) and I am wondering: I can use the construct operator to add an item to the beginning of a list: 1 : [2,3] [1,2,3] I tried making an example data type I found in the book and then playing with it: --in a file data BillingInfo = CreditCard Int String String | CashOnDelivery | Invoice Int deriving (Show) --in ghci $ let order_list = [Invoice 2345] $ order_list [Invoice 2345] $ let order_list = CashOnDelivery : order_list $ order_list [CashOnDelivery, CashOnDelivery, CashOnDelivery, CashOnDelivery, CashOnDelivery, CashOnDelivery, CashOnDelivery, CashOnDelivery, CashOnDelivery, CashOnDelivery, CashOnDelivery, CashOnDelivery, CashOnDelivery, CashOnDelivery, ...- etc... it just repeats forever, is this because it uses lazy evaluation? -- EDIT -- okay, so it is being pounded into my head that let order_list = CashOnDelivery:order_list doesn't add CashOnDelivery to the original order_list and then set the result to order_list, but instead is recursive and creates an infinite list, forever adding CashOnDelivery to the beginning of itself. Of course now I remember that Haskell is a functional language and I can't change the value of the original order_list, so what should I do for a simple "tack this on to the end (or beginning, whatever) of this list?" Make a function which takes a list and BillingInfo as arguments, and then return a list? -- EDIT 2 -- well, based on all the answers I'm getting and the lack of being able to pass an object by reference and mutate variables (such as I'm used to)... I think that I have just asked this question prematurely and that I really need to delve further into the functional paradigm before I can expect to really understand the answers to my questions... I guess what i was looking for was how to write a function or something, taking a list and an item, and returning a list under the same name so the function could be called more than once, without changing the name every time (as if it was actually a program which would add actual orders to an order list, and the user wouldn't have to think of a new name for the list each time, but rather append an item to the same list).

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• What's the best way of accessing a DRb object (e.g. Ruby Queue) from Scala (and Java)?

  - by Tom Morris

  I have built a variety of little scripts using Ruby's very simple Queue class, and share the Queue between Ruby and JRuby processes using DRb. It would be nice to be able to access these from Scala (and maybe Java) using JRuby. I've put together something Scala and the JSR-223 interface to access jruby-complete.jar. import javax.script._ class DRbQueue(host: String, port: Int) { private var engine = DRbQueue.factory.getEngineByName("jruby") private var invoker = engine.asInstanceOf[Invocable] engine.eval("require \"drb\" ") private var queue = engine.eval("DRbObject.new(nil, \"druby://" + host + ":" + port.toString + "\")") def isEmpty(): Boolean = invoker.invokeMethod(this.queue, "empty?").asInstanceOf[Boolean] def size(): Long = invoker.invokeMethod(this.queue, "length").asInstanceOf[Long] def threadsWaiting: Long = invoker.invokeMethod(this.queue, "num_waiting").asInstanceOf[Long] def offer(obj: Any) = invoker.invokeMethod(this.queue, "push", obj.asInstanceOf[java.lang.Object]) def poll(): Any = invoker.invokeMethod(this.queue, "pop") def clear(): Unit = { invoker.invokeMethod(this.queue, "clear") } } object DRbQueue { var factory = new ScriptEngineManager() } (It conforms roughly to java.util.Queue interface, but I haven't declared the interface because it doesn't implement the element and peek methods because the Ruby class doesn't offer them.) The problem with this is the type conversion. JRuby is fine with Scala's Strings - because they are Java strings. But if I give it a Scala Int or Long, or one of the other Scala types (List, Set, RichString, Array, Symbol) or some other custom type. This seems unnecessarily hacky: surely there has got to be a better way of doing RMI/DRb interop without having to use JSR-223 API. I could either make it so that the offer method serializes the object to, say, a JSON string and takes a structural type of only objects that have a toJson method. I could then write a Ruby wrapper class (or just monkeypatch Queue) to would parse the JSON. Is there any point in carrying on with trying to access DRb from Java/Scala? Might it just be easier to install a real message queue? (If so, any suggestions for a lightweight JVM-based MQ?)

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• Show random string.

  - by zaid

  i am trying to display a random string each time a button is pressed from a set of strings defined in strings.xml . this is an example of the strings ID's <string name="q0"> <string name="q1"> <string name="q2"> <string name="q3"> <string name="q4"> java code for getting a random string. private static final Random rgenerator = null; int RandomQ = R.string.q0 (rgenerator.nextInt(5) + 1); String q = getString(RandomQ); if i try to use this java code i get an error at "q0" in R.string.q0 which is The method q0(int) is undefined for the type R.string if i try to use the quick fix and create a method, it works. but it wont let me save or run the app because it replaces my create method and shows this message R.java was modified manually! Reverting to generated version! thanks for reading.

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• DefaultTableCellRenderer getTableCellRendererComponent never gets called

  - by Dean Schulze

  I need to render a java.util.Date in a JTable. I've implemented a custom renderer that extends DefaultTableCellRenderer (below). I've set it as the renderer for the column, but the method getTableCellRendererComponent() never gets called. This is a pretty common problem, but none of the solutions I've seen work. public class DateCellRenderer extends DefaultTableCellRenderer { String sdfStr = "yyyy-MM-dd HH:mm:ss.SSS"; SimpleDateFormat sdf = new SimpleDateFormat(sdfStr); public Component getTableCellRendererComponent(JTable table, Object value, boolean isSelected, boolean hasFocus, int row, int column) { super.getTableCellRendererComponent(table, value, isSelected, hasFocus, row, column); if (value instanceof Date) { this.setText(sdf.format((Date) value)); } else logger.info("class: " + value.getClass().getCanonicalName()); return this; } } I've installed the custom renderer (and verified that it has been installed) like this: DateCellRenderer dcr = new DateCellRenderer(); table.getColumnModel().getColumn(2).setCellRenderer(dcr); I've also tried table.setDefaultRenderer( java.util.Date.class, dcr ); Any idea why the renderer gets installed, but never called?

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• List overwriting data on all positions

  - by elvispt

  I created a class with 3 fields: class Gente { int _ID; string _nome, _sexo; public Gente() { _ID = 0; _nome = ""; _sexo = ""; } public int ID { set { _ID = value; } get { return _ID; } } public string Nome { set { _nome = value; } get { return _nome; } } public string Sexo { set { _sexo = value; } get { return _sexo; } } } Then I declared a List from that class and an object from that class so that I can be able to add to the List. List<Gente> Alunos = new List<Gente>(); Gente professor = new Gente(); The first time I do the Alunos.Add(professor); to the list it correctly sends the information to the 0 position. But when I do it second time it overwrites everything on position 0 with the new data besides adding the new data to a new position, 1.

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• Actionscript Enterframe Movement

  - by David

  I am trying to make accelerated movement, but I am running into a problem that, for the life of me, I cannot understand. My class definition: public class Player extends MovieClip { private var stageRef:Stage; private var key:KeyObject; private var acceleration:int = .5; private var curSpeed:int = 0; public function Player(stageRef:Stage) { this.stageRef = stageRef; addEventListener(Event.ENTER_FRAME, enterFrame); key = new KeyObject(stageRef); } public function enterFrame(e:Event) : void { if(key.isDown(key.RIGHT)) { x += 5; } } } This works to move my position in the x direction at a constant rate. However, if I change enterFrame to public function enterFrame(e:Event) : void { if(key.isDown(key.RIGHT)) { x += acceleration; } } No movement occurs. Is there something going on in the event I do not understand? Why is it that I can have x increased by a constant value but not a constant value as defined in a variable in the class? Is it a scope issue?

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• GetAccessControl error with NTAccount

  - by Adam Witko

  private bool HasRights(FileSystemRights fileSystemRights_, string fileName_, bool isFile_) { bool hasRights = false; WindowsIdentity WinIdentity = System.Security.Principal.WindowsIdentity.GetCurrent(); WindowsPrincipal WinPrincipal = new WindowsPrincipal(WinIdentity); AuthorizationRuleCollection arc = null; if (isFile_) { FileInfo fi = new FileInfo(@fileName_); arc = fi.GetAccessControl().GetAccessRules(true, true, typeof(NTAccount)); } else { DirectoryInfo di = new DirectoryInfo(@fileName_); arc = di.GetAccessControl().GetAccessRules(true, true, typeof(NTAccount)); } foreach (FileSystemAccessRule rule in arc) { if (WinPrincipal.IsInRole(rule.IdentityReference.Value)) { if (((int)rule.FileSystemRights & (int)fileSystemRights_) > 0) { if (rule.AccessControlType == AccessControlType.Allow) hasRights = true; else if (rule.AccessControlType == AccessControlType.Deny) { hasRights = false; break; } } } } return hasRights; } The above code block is causing me problems. When the WinPrincipal.IsInRole(rule.IdentityReference.Value) is executed the following exception occurs: "The trust relationship between the primary domain and the trusted domain failed.". I'm very new to using identities, principles and such so I don't know what's the problem. I'm assuming it's with the use of NTAccount? Thanks

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• Error Reading Image

  - by javawarrior

  When I tried to open a simple smile.png image using package com.java3d.java3d.graphics; import java.awt.Color; import java.awt.image.BufferedImage; import java.io.File; import javax.imageio.ImageIO; public class Texture { public static Render floor = loadBitMap("smile.png"); public Texture(){} public static Render loadBitMap(String fileName) { try { BufferedImage image = ImageIO.read(Thread.currentThread().getContextClassLoader().getResource(fileName)); System.out.print(image==null); int width = image.getWidth(); System.out.println(width); int height = image.getHeight(); System.out.println(height); System.out.println(image.getRGB(4, 4)); Render result = new Render(width, height); image.getRGB(0, 0, width, height, result.pixels, 0, width); return result; } catch (Exception e) { System.out.println("CRASH!"); throw new RuntimeException(e); } } } it returns every pixel as -1; what could be causing this problem? Here is the image:

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