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• Is it bad practice to use python's getattr extensively?

  - by Wilduck

  I'm creating a shell-like environment. My original method of handleing user input was to use a dictionary mapping commands (strings) to methods of various classes, making use of the fact that functions are first class objects in python. For flexibility's sake (mostly for parsing commands), I'm thinking of changing my setup such that I'm using getattr(command), to grab the method I need and then passing arguments to it at the end of my parser. Another advantage of this approach is not having to update my (currently statically implemented) command dictionary every time I add a new method/command. My question is, will I be taking a hit to the efficiency of my shell? Does it matter how many methods/commands I have? I'm currently looking at 30 some commands, which could eventually double.

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• STL map containing references does not compile

  - by MTsoul

  The following: std::map<int, ClassA &> test; gives: error C2101: '&' on constant While the following std::map<ClassA &, int> test; gives error C2528: '_First' : pointer to reference is illegal The latter seems like map cannot contain a reference for the key value, since it needs to instantiate the class sometimes and a reference cannot be instantiated without an object. But why does the first case not work?

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• Socket programming question

  - by dfddf

  I am given the following declaration: char inbuff[500], *ptr; int n, bufferlen; Write a program segement to receive a message having 500 bits from the TCP socket sock and store this message in inbuff. My answer is: n = recv( sock, inbuff, strlen( inbuff ), 0 ); However, I am not sure why *ptr is given in the declaration. So, I would like ask, what is the purpose of the pointer in this question?? Or my program segement is wrong? Thank you for all of yours help first!

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• ANTLR - Embedding Java code, evaluate before or after?

  - by wvd

  Hello all, I'm writing a simple scripting language on top of Java/JVM, where you can also embed Java code using the {} brackets. The problem is, how do I parse this in the grammar? I have two options: 1] Allow everything to be in it, such as: [a-z|a-Z|0-9|_|$], and go on 2] Get an extra java grammar and use that grammar to parse that small code (is it actually possible and efficient?) Since option 2] is basically a double-check since when evaluating java code it's also being checked. Now my last question is -- is way that can dynamically execute java code also with objects which have been created at runtime? Thanks, William van Doorn

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• C++ - Opening a file inside a function using fopen

  - by Josh

  I am using Visual Studio 2005 (C++). I am passing a string into a function as a char array. I want to open the file passed in as a parameter and use it. I know my code works to an extent, because if I hardcode the filename as the first parameter it works perfectly. I do notice if I look at the value as a watch, the value includes the address aside the string literal. I have tried passing in the filename as a pointer, but it then complains about type conversion with __w64. As I said before it works fine with "filename.txt" in place of fileName. I am stumped. void read(char fileName[50],int destArray[MAX_R][MAX_C],int demSize[2]) { int rows=0; int cols=0; int row=0; int col=0; FILE * f = fopen(fileName,"r"); ...

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• HTML stops at a PHP script made to connect to a mysql database. No errors printed.

  - by DavidR

  I'm trying to set up a login script for PHP using the tutorial on this site. The problem is that the site stops when it hits these lines, no error, no text: <?php $conn = mysql_connect('localhost', 'root', 'password') or die('error line7' . mysql_error()); mysql_select_db('mydb', $conn) or die('error line8' . mysql_error()); ?> If I take out these lines, the rest of the html runs perfectly. I've double checked my passwords and everything, nothing is working. I know very little about php and mysql other than what I've learned trying to set this up.

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• numpy array C api

  - by wiso

  I have a C++ function returning a std::vector and I want to use it in python, so I'm using the C numpy api: static PyObject * py_integrate(PyObject *self, PyObject *args){ ... std::vector<double> integral; cpp_function(integral); // this change integral npy_intp size = {integral.size()}; PyObject *out = PyArray_SimpleNewFromData(1, &size, NPY_DOUBLE, &(integral[0])); return out; } when I call it from python, if I do import matplotlib.pyplot as plt a = py_integrate(parameters) print a fig = plt.figure() ax = fig.add_subplot(111) ax.plot(a) print a the first print is ok, the values are correct, but when I plot a they are not, and in particular in the second print I see very strange values like 1E-308 1E-308 ... or 0 0 0 ... as an unitialized memory. I don't understand why the first print is ok.

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• C# implicit conversions and == operator

  - by Arnis L.

  Some code for context: class a { } class b { public a a{get;set;} public static implicit operator a(b b) { return b.a; } } a a=null; b b=null; a = b; //compiler: cannot apply operator '==' to operands of type tralala... bool c = a == b; Is it possible to use == operator on different type instances, where one can implicitly convert to another? What did i miss? Edit: If types must be the same calling ==, then why int a=1; double b=1; bool c=a==b; works?

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• C++ initializing constants and inheritance

  - by pingvinus

  I want to initialize constant in child-class, instead of base class. And use it to get rid of dynamic memory allocation (I know array sizes already, and there will be a few child-classes with different constants). So I try: class A { public: const int x; A() : x(0) {} A(int x) : x(x) {} void f() { double y[this->x]; } }; class B : A { B() : A(2) {} }; Pretty simple, but compiler says: error C2057: expected constant expression How can I say to compiler, that it is really a constant?

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• How can I highlight the line of text that is closest to the mouse?

  - by Aaron Digulla

  I have a long text and I'd like to offer the user a reading help: The current line should be highlighted. To make it easier, I'll just use the Y coordinate of the mouse (this way, the mouse pointer isn't going to get in the way). I have a big DIV with the id content which fills the whole width and a small DIV with the class content for the text (see here for an example). I'm using jQuery 1.4. How can I highlight the line of text that is closest to the current mouse position?

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• How to corelate gtk.ListStore items with my own models

  - by Victor Stanciu

  Hello, I have a list of Project objects, that I display in a GTK TreeView. I am trying to open a dialog with a Project's details when the user double-clicks on the item's row in the TreeView. Right now I get the selected value from the TreeView (which is the name of the Project) via get_selection(), and search for that Project by name in my own list to corelate the selection with my own model. However, this doesn't feel quite right (plus, it assumes that a Project's name is unique), and I was wondering if there is a more elegant way of doing it.

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• Speed up math code in C# by writing a C dll?

  - by Projectile Fish

  I have a very large nested for loop in which some multiplications and additions are performed on floating point numbers. for (int i = 0; i < length1; i++) { s = GetS(i); c = GetC(i); for(int j = 0; j < length2; j++) { double oldU = u[j]; u[j] = c * oldU + s * omega[i][j]; omega[i][j] = c * omega[i][j] - s * oldU; } } This loop is taking up the majority of my processing time and is a bottleneck. Would I be likely to see any speed improvements if I rewrite this loop in C and interface to it from C#?

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• How to call an event when the user "finally" selects an item in a list?

  - by herzmeister der welten

  When a user clicks once on an item in a Grid or a ListBox, that item is usually selected, hence most UI frameworks have a onSelected event or the like for that. However, how can we generally call the next step when a user "finally" selects an item by e.g. double clicking an entry? You know when some popup might appear in the context of the selected item and the user can do further stuff. Strangely enough, I think I have never seen a word for that in any UI framework. onPicked, onAccepted, onChosen, onFinallySelected, onResult? All kinda awkward or too special. Any other ideas?

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• Stacking a View with the Editor Area?

  - by Patrick

  Hello everybody, :-) Is it possible, when developing an Eclipse RCP Application, to stack a view with the editor area? Like this? http://www.fotos-hochladen.net/stackingaviewwithane9e1fdbvp.png I have multiple lists / tables. I want to create a kind of preview composite. When an Item on a list is selected by single mouse click, i want my preview composite to show the data of the item. If the user double clicks an item, i want to open an editor in the stack behind the preview composite. Is there anyway to achieve this? Thanks Patrick :-)

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• Reading in 4 bytes at a time

  - by alphomega

  I have a big file full of integers that I'm loading in. I've just started using C++, and I'm trying out the filestream stuff. From everything I've read, it appears I can only read in bytes, So I've had to set up a char array, and then cast it as a int pointer. Is there a way I can read in 4 bytes at a time, and eliminate the need for the char array? const int HRSIZE = 129951336; //The size of the table char bhr[HRSIZE]; //The table int *dwhr; int main() { ifstream fstr; /* load the handranks.dat file */ std::cout << "Loading table.dat...\n"; fstr.open("table.dat"); fstr.read(bhr, HRSIZE); fstr.close(); dwhr = (int *) bhr; }

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• A question on vectors, pointers and iterators

  - by xbonez

  Guys, I have a midterm examination tomorrow, and I was looking over the sample paper, and I'm not sure about this question. Any help would be appreciated. Let v be a vector<Thingie*>, so that each element v[i] contains a pointer to a Thingie. If p is a vector<Thingie*>::iterator, answer the following questions: what type is p? what type is *p? what code provides the address of the actual Thingie? what code provides the actual Thingie?

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• multiple C++ deletion of a memory pointed by multiple objects

  - by elgcom

  Another c++ pointer deletion question is in the following example: class Foo { public: int *p; ~Foo() { delete p; p = NULL; } }; Foo *f1 = new Foo(); Foo *f2 = new Foo(); f1->p = new int(1); f2->p = f1->p; delete f2; // ok delete f1; // no error? Why I did not get error when calling "delete f1"? didn't I delete the same address (*p) twice? If I directly delete the pointers in the last 2 lines of code, I will get error. delete f2->p; // ok delete f1->p; // error!! *** glibc detected *** double free or corruption (fasttop) ***

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• What coding standards do you follow?

  - by Mark Szymanski

  I was just curious what coding standards people followed. I for one use the following: Brackets ALWAYS go on the next line. For instance: int main() { //Blah... } I never use code folding. (Yes my IDE's do support it (Xcode and Eclipse). Put related functions/methods single-spaced, otherwise double space. Here is an example: int foo = 0; printf("%d",foo); those are related while these are not: printf("Hello, World!"); return(0); I don't put else statements on the same line as the closing bracket for the preceding if statement. Most of the time in Java if a program needs multiple try catch statements I will just put the whole thing in one try catch.

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• Can jQuery UI's Sortable handle complex selectors for the items option?

  - by jverdi

  I have list items in an unordered list that when double clicked, can be edited in place via a wysiwyg editor. $('ul.mtm_section').sortable({ disabled: true, distance: 10, items: '> li:not(:has(form))' }); My goal is to prevent the list item from being sorted while it is being edited - aka once a form element has been swapped in place of the contents. Unfortunately my selector for items is not working. Is sortable able to handle complex selectors like these? If not, are there other clever means to disable some items from being sortable, perhaps a callback function? I would prefer to rely on this sortable option, as the wysiwyg plugin is deeply nested with jEditable and as far as I know does not open up any events for me to hook into. Using jQuery 1.4.2 and jQuery UI 1.8.1

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• Syntax error in SharePoint calculated column formula

  - by Jan Aagaard

  Is it possible to debug SharePoint calculated column formulas? I am trying with a really simple SharePoint calculated formula =IF([YTD]<[Budget], "OK", "Not OK"). This being a Danish installations of SharePoint I believe the fomula should look like this: =HVIS([YTD]<=[Budget]; "OK"; "Not OK") But this just leaves with the same syntax error or not supported error. I have tried all combinations of IF/HVIS, with/without the square brackets, comma/semicolon, single quotes/double quotes, but nothing works. The formula =YTD<=Budget works.

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• passing parameters to javacsript using php

  - by ayush

  i have the following line of code - <a href="javascript:;" onClick="tweeet('myid')">My Tweets!</a> Now while this is working perfectly fine the following line is not - <a href="javascript:;" onClick="tweeet(<?php echo 'myid'; ?>)">My Tweets!</a> Can anyone help me out why it is not working and suggest any changes. The variable i want to pass to the javascript function is a php variable. also i have tried the php with single quotes and double quotes but it is not working.

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• Simple question C#.net about if else statement

  - by ilkdrl

  Iam doing a simple website and when i press button, i should see weight in label.. i see but if text.maxlenght 6, i should see ERROR message in same label but repeat see weight in label. How can i solve this problem? protected void Button1_Click(object sender, EventArgs e) { double sayi1, sayi2, sayi3, hesap, sonuc; sayi1 = Convert.ToDouble(Tb1.Text); sayi2 = Convert.ToDouble(Tb2.Text); sayi3 = Convert.ToDouble(Tb3.Text); if (Tb1.MaxLength > 6 || Tb2.MaxLength > 6) { lbl1.Text = "ERROR."; } else { hesap = (((sayi1 - ((sayi1 - sayi2) / 2)) * ((sayi1 - sayi2) / 2)) / 40); sonuc = (hesap * sayi3) / 100; lbl1.Text = sonuc.ToString() + "kg"; } }

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• 2 Classes need each other declared C++

  - by Prodigga

  I have a "Game" class which holds all the games settings and manages the game. I have a "Grid" class which is the grid the game is played on. The "Game" class initializes a "Grid" object as one of its members (passing itself ("this") as one of the parameters for "Grid"s constructor).. The "Grid" object therefor needs to deal with a "Game*" pointer. To do this it needs to know what "Game" is; i need to declare it before "Grid". But "Game" uses "Grid"...so it also needs "Grid" declared before it. so confused on how to include headers/etc correctly here..

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• Struct size containing vector<T> different sizes between DLL and EXE..

  - by Michael Peddicord

  I have this situation where an EXE program imports a DLL for a single function call. It works by passing in a custom structure and returning a different custom structure. Up till now it's worked fine until I wanted one of the structs data members to be a vector < MyStruct When I do a sizeof(vector< MyStruct ) in my program I get a size of 20 but when I do it from inside the DLL I get a size of 24. This size inconsistency is causing a ESP pointer error. Can anyone tell me why a Vector < MyStruct would be a different size in the DLL than in the program? I have reverified that my structs in both the DLL and the Program are identical. I would appreciate any help on the subject. Thank you.

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• How to sanely read and dump structs to disk when some fields are pointers?

  - by bp

  Hello, I'm writing a FUSE plugin in C. I'm keeping track of data structures in the filesystem through structs like: typedef struct { block_number_t inode; filename_t filename; //char[SOME_SIZE] some_other_field_t other_field; } fs_directory_table_item_t; Obviously, I have to read (write) these structs from (to) disk at some point. I could treat the struct as a sequence of bytes and do something like this: read(disk_fd, directory_table_item, sizeof(fs_directory_table_item_t)); ...except that cannot possibly work as filename is actually a pointer to the char array. I'd really like to avoid having to write code like: read(disk_df, *directory_table_item.inode, sizeof(block_number_t)); read(disk_df, directory_table_item.filename, sizeof(filename_t)); read(disk_df, *directory_table_item.other_field, sizeof(some_other_field_t)); ...for each struct in the code, because I'd have to replicate code and changes in no less than three different places (definition, reading, writing). Any DRYer but still maintainable ideas?

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