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  • I know the big picture but can't put it in place

    - by Simbilim
    Hi, I'm interested in web development and by that I mean the bigger projects like facebook or twitter. I know the basics of java, css, php and mysql. I know there is a lot more out there. I read about it. But I don't know what the purpose is and how to put in place. Things like: Scribe, thrift, casandra, Unix/Linux, shell/perl/python scripting, PostgreSQL, MongoDB, non-relational NoSQL datastores, JVM, nginx I want to know why they need it, how they use it and what te purpose is. What I need is a book like technical background of facebook for dummies or so. Are there any books or websites that explain this from scratch? Thank you!

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  • How to wrap a C function whose parameters are pointer to structs, so that it can be called from Lua?

    - by pierr
    I have the follwing C function. How should I wrap it so it can be called from a Lua script? typedef struct tagT{ int a ; int b ; } type_t; int lib_a_f_4(type_t *t) { return t->a * t->b ; } I know how to wrapr it if the function parameter type were int or char *. Should I use table type for a C structure? EDIT: I am using SWIG for the wraping , according to this doc, It seems that I should automatically have this funtion new_type_t(2,3) , but it is not the case. If you wrap a C structure, it is also mapped to a Lua userdata. By adding a metatable to the userdata, this provides a very natural interface. For example, struct Point{ int x,y; }; is used as follows: p=example.new_Point() p.x=3 p.y=5 print(p.x,p.y) 3 5 Similar access is provided for unions and the data members of C++ classes. C structures are created using a function new_Point(), but for C++ classes are created using just the name Point().

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  • What are "named tuples" in Python?

    - by Denilson Sá
    Reading the changes in Python 3.1, I found something... unexpected: The sys.version_info tuple is now a named tuple: I never heard about named tuples before, and I thought elements could either be indexed by numbers (like in tuples and lists) or by keys (like in dicts). I never expected they could be indexed both ways. Thus, my questions are: What are named tuples? How to use them? Why/when should I use named tuples instead of normal tuples? Why/when should I use normal tuples instead of named tuples? Is there any kind of "named list" (a mutable version of the named tuple)?

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  • mapping list of different types implementing same function?

    - by sisif
    I want to apply a function to every element in a list (map) but the elements may have different types but all implement the same function (here "putOut") like an interface. However I cannot create a list of this "interface" type (here "Outputable"). How do I map a list of different types implementing the same function? main :: IO () main = do map putOut lst putStrLn "end" where lst :: [Outputable] -- ERROR: Class "Outputable" used as a type lst = [(Out1 1),(Out2 1 2)] class Outputable a where putOut :: a -> IO () -- user defined: data Out1 = Out1 Int deriving (Show) data Out2 = Out2 Int deriving (Show) instance Outputable Out1 where putOut out1 = putStrLn $ show out1 instance Outputable Out2 where putOut out2 = putStrLn $ show out2 I cannot define it this way: data Out = Out1 Int | Out2 Int Int putOut Out1 = ... putOut Out2 = ... because this is a library and users should be able to extend Out with their own types

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  • C++ function-pointer and inheritance

    - by pingvinus
    In parent class I have function, that operates under an array of functions, declared in child-class, number of functions for every child-class may vary. But since every function uses some object-variables, I can't declare them as static. I've try to do something like this: class A { public: typedef int (A::*func)(); func * fs; void f() { /*call functions from this->fs*/ } }; class B : public A { public: int smth; B(int smth) { this->smth = smth; this->fs = new func[1]; fs[0] = &B::f; } int f() { return smth + 1; } }; But, obviously it doesn't work. Any suggestions?

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  • Java NullPointerException. Why?

    - by user292844
    I am new to Java. I just read that class variables in Java have default value. I tried the following program. I was expecting to get the output as 0, which is the default value on an integer, but I get the NullPointerException. What am I missing? class Test{ static Integer iVar; public static void main(String...args) { System.out.println(iVar.intValue()); } }

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  • How to append() an element and set its style with css() at the same time with jQuery

    - by Acorn
    I tried: $('#canvas').append('<div class="tile"></div>').css({left: leftPos, top: topPos});, but that sets the style of #canvas rather than the appended element. I then tried: $('#canvas').append(('<div class="tile"></div>').css({left: leftPos, top: topPos}));, but that gives the error "Object <div class="tile"></div> has no method 'css'". How can I add the element and set its style at the same time?

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  • for line in open(filename)

    - by foosion
    I frequently see python code similar to for line in open(filename): do_something(line) When does filename get closed with this code? Would it be better to write with open(filename) as f: for line in f.readlines(): do_something(line)

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  • Codeigniter: simple form function

    - by Kevin Brown
    I'm stuck writing a simple form...I feel dumb. Here's my controller: function welcome_message(){ //Update welcome message $id = $this->session->userdata('id'); $profile['welcome_message'] = $this->input->post('welcome_message'); $this->db->update('be_user_profiles',$profile, array('user_id' => $id)); } And the html: <?php print form_open('home/welcome_message')?> <input type="checkbox" value="0" checked="false">Don't show me this again</input> <p> <input class="button submit" type="submit" class="close-box" value="Close" /> </p> <?php print form_close()?> Edit I simply need it to submit to a private function and return to the home page (page submitted from).

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  • C++: Trouble with templates (C2064)

    - by Rosarch
    I'm having compiler errors, and I'm not sure why. What am I doing wrong here: Hangman.cpp: set<char> Hangman::incorrectGuesses() { // Hangman line 103 return Utils::findAll_if<char>(guesses.begin(), guesses.end(), &Hangman::isIncorrectGuess); } bool Hangman::isIncorrectGuess(char c) { return correctAnswer.find(c) == string::npos; } Utils.h: namespace Utils { void PrintLine(const string& line, int tabLevel = 0); string getTabs(int tabLevel); template<class result_t, class Predicate> std::set<result_t> findAll_if(typename std::set<result_t>::iterator begin, typename std::set<result_t>::iterator end, Predicate pred) { std::set<result_t> result; // utils line 16 return detail::findAll_if_rec<result_t>(begin, end, pred, result); } } namespace detail { template<class result_t, class Predicate> std::set<result_t> findAll_if_rec(typename std::set<result_t>::iterator begin, typename std::set<result_t>::iterator end, Predicate pred, std::set<result_t> result) { // utils line 25 typename std::set<result_t>::iterator nextResultElem = find_if(begin, end, pred); if (nextResultElem == end) { return result; } result.insert(*nextResultElem); return findAll_if_rec(++nextResultElem, end, pred, result); } } This produces the following compiler errors: algorithm(83): error C2064: term does not evaluate to a function taking 1 arguments algorithm(95) : see reference to function template instantiation '_InIt std::_Find_if<std::_Tree_unchecked_const_iterator<_Mytree>,_Pr>(_InIt,_InIt,_Pr)' being compiled 1> with 1> [ 1> _InIt=std::_Tree_unchecked_const_iterator<std::_Tree_val<std::_Tset_traits<char,std::less<char>,std::allocator<char>,false>>>, 1> _Mytree=std::_Tree_val<std::_Tset_traits<char,std::less<char>,std::allocator<char>,false>>, 1> _Pr=bool (__thiscall Hangman::* )(char) 1> ] utils.h(25) : see reference to function template instantiation '_InIt std::find_if<std::_Tree_const_iterator<_Mytree>,Predicate>(_InIt,_InIt,_Pr)' being compiled 1> with 1> [ 1> _InIt=std::_Tree_const_iterator<std::_Tree_val<std::_Tset_traits<char,std::less<char>,std::allocator<char>,false>>>, 1> _Mytree=std::_Tree_val<std::_Tset_traits<char,std::less<char>,std::allocator<char>,false>>, 1> Predicate=bool (__thiscall Hangman::* )(char), 1> _Pr=bool (__thiscall Hangman::* )(char) 1> ] utils.h(16) : see reference to function template instantiation 'std::set<_Kty> detail::findAll_if_rec<result_t,Predicate>(std::_Tree_const_iterator<_Mytree>,std::_Tree_const_iterator<_Mytree>,Predicate,std::set<_Kty>)' being compiled 1> with 1> [ 1> _Kty=char, 1> result_t=char, 1> Predicate=bool (__thiscall Hangman::* )(char), 1> _Mytree=std::_Tree_val<std::_Tset_traits<char,std::less<char>,std::allocator<char>,false>> 1> ] hangman.cpp(103) : see reference to function template instantiation 'std::set<_Kty> Utils::findAll_if<char,bool(__thiscall Hangman::* )(char)>(std::_Tree_const_iterator<_Mytree>,std::_Tree_const_iterator<_Mytree>,Predicate)' being compiled 1> with 1> [ 1> _Kty=char, 1> _Mytree=std::_Tree_val<std::_Tset_traits<char,std::less<char>,std::allocator<char>,false>>, 1> Predicate=bool (__thiscall Hangman::* )(char) 1> ]

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  • Setting the rank of a user-defined verb in J

    - by Gregory Higley
    Here's a function to calculate the digital sum of a number in J: digitalSum =: +/@:("."0)@": If I use b. to query the rank of this verb, I get _ 1 _, i.e., infinite. (We can ignore the dyadic case since digitalSum is not dyadic.) I would like the monadic rank of this verb to be 0, as reported by b.. The only way I know of to do this is to use a "shim", e.g., ds =: +/@:("."0)@": digitalSum =: ds"0 This works great, but I want to know whether it's the only way to do this, or if there's something else I'm missing.

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  • [solved] What's wrong with this jQuery example?

    - by Sven Larson
    The following jQuery example should put some text into the div, but it doesn't. I tried Firefox, Google Chrome and Internet Explorer. <html> <head> <script src="http://ajax.googleapis.com/ajax/libs/jquery/1.4.2/jquery.min.js" language="javascript"></script> <script language="javascript"> $(window).load(function() { $('adiv').html('<p>hello world</p>'); alert('done'); }); </script> </head> <body> <div id="adiv"> </div> </body> </html> Sorry, this might be stupid, but I'm stuck.

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  • How to join list of strings?

    - by satsurae
    Hi all, This is probably seriously easy to solve for most of you but I cannot solve this simply putting str() around it can I? I would like to convert this list: ['A','B','C'] into 'A B C'. Thanks in advance!!

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  • how to see contents of a.out file?

    - by abhilashm86
    The executable file of c++ will contain linkers, modules and others, i would like to look into its contents, i'm using linux, how can i view contents of a.out? which command should use to browse a.out, text editors wont show the contents......

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  • how to start learning JavaScript

    - by antriksh
    Dear All, I am experienced in the technical support like Linux, oracle, sunos etc and but if i say scripting i know little bit of bash. Now i promoted to manage technical engineers including some JavaScript developers, so i want to learn JavaScripting so that i can understand engineers. Hope you understand. Can you please advise me how can i start JavaScripting and point me to some simple docs and examples.

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  • number of elements in a static array of a predefined size

    - by cppb
    I have an array like this: int a[100]; I am filling only the first 4 elements in this array: a[0] = 1; a[1] = 2; a[2] = 3; a[3] = 4; When I do sizeof(a)/sizeof(a[0]) it returns 100. Is there a way I can get number of elements to which I have assinged a value and thus filtering out the remaining 96 unassigned elements? thanks

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  • How do I convert a simple ruby flashcard program into a ROR app?

    - by Mark Wilbur
    What I'm trying to do is make a basic flashcard app on rails. At this point, all I'm looking for is the functionality to iterate through a list of flashcards, quiz the user and let the user know if they were right or not. In ruby, it didn't take me long to write: class Card attr_accessor :answer, :question def initialize(answer = "", question="") @answer = answer @question = question end def quiz puts "What does #@question mean?" answer = gets.chomp if answer == @answer puts "Right" return true else puts "Wrong" return answer end end end class Cardlist attr_accessor :Cards def initialize(Cards = []) @Cards = Cards end def quiz Cards.each do |w| w.quiz end end end The problem I'm having with rails is figuring out where to put the logic to loop through all the cards in the list. I've made models specifying that Card belongs_to cardlist and that Cardlist has_many cards. I know application logic should go in the controller, but if I were to make a "quiz" action for my Cardlist controller, how would I make it iterate through all the cards? After each "quiz" page generated, I'd need to get an answer back from the user, respond (maybe flash) whether it was right or not and then continue onto the next question. Would any of that logic have to go into the view in order to make sure it's sending back the user inputted answers to the controller?

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  • Help C++ifying this C style code.

    - by Flamewires
    Hey I'm used to developing in C and I would like to use C++ in a project. Can anyone give me an example of how I would translate this C-style code into C++ code. I know it should compile in a c++ complier but I'm talking using c++ techniques(I.e. classes, RAII) typedef struct Solution Solution; struct Solution { double x[30]; int itt_found; double value; }; Solution *NewSolution() { Solution *S = (Solution *)malloc(sizeof(Solution)); for (int i=0;<=30;i++) { S-x[i] = 0; } S-itt_found = -1; return S; } void FreeSolution(Solution *S) { if (S != NULL) free(S); } int main() { Solution *S = NewSolution(); S-value = eval(S-x);// evals is another function that returns a double S-itt_found = 0; FreeSolution(S); return EXIT_SUCCESS; } Ideally I would like to be able to so something like this in main, but I'm not sure exactly how to create the class, i've read a lot of stuff but incorporating it all together correctly seems a little hard atm. Solution S(30);//constructor that takes as an argument the size of the double array S.eval();//a method that would run eval on S.x[] and store result in S.value cout << S.value << endl; Ask if you need more info, thanks.

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  • "Function object is unsubscriptable" in basic integer to string mapping function

    - by IanWhalen
    I'm trying to write a function to return the word string of any number less than 1000. Everytime I run my code at the interactive prompt it appears to work without issue but when I try to import wordify and run it with a test number higher than 20 it fails as "TypeError: 'function' object is unsubscriptable". Based on the error message, it seems the issue is when it tries to index numString (for example trying to extract the number 4 out of the test case of n = 24) and the compiler thinks numString is a function instead of a string. since the first line of the function is me defining numString as a string of the variable n, I'm not really sure why that is. Any help in getting around this error, or even just help in explaining why I'm seeing it, would be awesome. def wordify(n): # Convert n to a string to parse out ones, tens and hundreds later. numString = str(n) # N less than 20 is hard-coded. if n < 21: return numToWordMap(n) # N between 21 and 99 parses ones and tens then concatenates. elif n < 100: onesNum = numString[-1] ones = numToWordMap(int(onesNum)) tensNum = numString[-2] tens = numToWordMap(int(tensNum)*10) return tens+ones else: # TODO pass def numToWordMap(num): mapping = { 0:"", 1:"one", 2:"two", 3:"three", 4:"four", 5:"five", 6:"six", 7:"seven", 8:"eight", 9:"nine", 10:"ten", 11:"eleven", 12:"twelve", 13:"thirteen", 14:"fourteen", 15:"fifteen", 16:"sixteen", 17:"seventeen", 18:"eighteen", 19:"nineteen", 20:"twenty", 30:"thirty", 40:"fourty", 50:"fifty", 60:"sixty", 70:"seventy", 80:"eighty", 90:"ninety", 100:"onehundred", 200:"twohundred", 300:"threehundred", 400:"fourhundred", 500:"fivehundred", 600:"sixhundred", 700:"sevenhundred", 800:"eighthundred", 900:"ninehundred", } return mapping[num] if __name__ == '__main__': pass

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