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• Search algorithm (with a sort algorithm already implemented)

  - by msr

  Hello, Im doing a Java application and Im facing some doubts in which concerns performance. I have a PriorityQueue which guarantees me the element removed is the one with greater priority. That PriorityQueue has instances of class Event (which implements Comparable interface). Each Event is associated with a Entity. The size of that priorityqueue could be huge and very frequently I will have to remove events associated to an entity. Right now Im using an iterator to run all the priorityqueue. However Im finding it heavy and I wonder if there are better alternatives to search and remove events associated with an entity "xpto". Any suggestions? Thanks!

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• Iteration through std containers in openmp

  - by Sasun Hambardzumyan

  Hi, people. I try to use openmp for multithreading the loop through std::set. When I write the following code - #pragma omp parallel for for (std::set<A>::const_iterator i = s.begin(); i != s.end(); ++i) { const A a = *i; operate(a); } I get an error - error: invalid type for iteration variable 'i' error: invalid controlling predicate error: invalid increment expression. So is there an another way to correct iteration in std containers using openmp? There is a workaround to use int i and iterate from 0 to s.size() and using iterator inside a loop body, but this is not looks good.

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• Coroutines in C#

  - by eyal

  I am looking to implement co-routines (user schedualed threads) in c#. When using c++ I was previously using fibers. As I see on the internet fibers do not exist in C#. I would like to get simillar functionality. Is there any "right" way to implement coroutines in c#? I have thought of implementing this using threads that aqcuire a single exection mutex + 1 one schedualer thread which releases this mutex for each coroutine. But this seems very costly (it forces a context switch between each coroutine) I have also seen the yeild iterator functionality, but as I understand you can't yeild within an internal function (only in the original ienumerator function). So this does me little good.

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• Python + MySQLdb executemany

  - by lhahne

  I'm using Python and its MySQLdb module to import some measurement data into a Mysql database. The amount of data that we have is quite high (currently about ~250 MB of csv files and plenty of more to come). Currently I use cursor.execute(...) to import some metadata. This isn't problematic as there are only a few entries for these. The problem is that when I try to use cursor.executemany() to import larger quantities of the actual measurement data, MySQLdb raises a TypeError: not all arguments converted during string formatting My current code is def __insert_values(self, values): cursor = self.connection.cursor() cursor.executemany(""" insert into values (ensg, value, sampleid) values (%s, %s, %s)""", values) cursor.close() where values is a list of tuples containing three strings each. Any ideas what could be wrong with this? Edit: The values are generated by yield (prefix + row['id'], row['value'], sample_id) and then read into a list one thousand at a time where row is and iterator coming from csv.DictReader.

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• Add functions in gdb at runtime

  - by Michael Anderson

  I'm trying to debug some STL based C++ code in gdb. The code has something like int myfunc() { std::map<int,int> m; ... } Now in gdb, inside myfunc using "print m" gives something very ugly. What I've seen recommended is compiling something like void printmap( std::map<int,int> m ) { for( std::map<int,int>::iterator it = ... ) { printf("%d : %d", it->first, it->second ); } } Then in gdb doing (gdb) call printmap( m ) This seems like a good way to handle the issue... but can I put printmap into a seperate object file (or even dynamic library) that I then load into gdb at runtime rather than compiling it into my binary - as recompiling the binary every time I want to look at another STL variable is not fun .. while compiling and loading a single .o file for the print routine may be acceptable.

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• How do I run gtk demos?

  - by Runner

  They are located under: share\gtk-2.0\demo But none of them contains a main function, how can I make the following textscroll.c actually work: /* Text Widget/Automatic scrolling * * This example demonstrates how to use the gravity of * GtkTextMarks to keep a text view scrolled to the bottom * while appending text. */ #include <gtk/gtk.h> #include "demo-common.h" /* Scroll to the end of the buffer. */ static gboolean scroll_to_end (GtkTextView *textview) { GtkTextBuffer *buffer; GtkTextIter iter; GtkTextMark *mark; char *spaces; static int count; buffer = gtk_text_view_get_buffer (textview); /* Get "end" mark. It's located at the end of buffer because * of right gravity */ mark = gtk_text_buffer_get_mark (buffer, "end"); gtk_text_buffer_get_iter_at_mark (buffer, &iter, mark); /* and insert some text at its position, the iter will be * revalidated after insertion to point to the end of inserted text */ spaces = g_strnfill (count++, ' '); gtk_text_buffer_insert (buffer, &iter, "\n", -1); gtk_text_buffer_insert (buffer, &iter, spaces, -1); gtk_text_buffer_insert (buffer, &iter, "Scroll to end scroll to end scroll " "to end scroll to end ", -1); g_free (spaces); /* Now scroll the end mark onscreen. */ gtk_text_view_scroll_mark_onscreen (textview, mark); /* Emulate typewriter behavior, shift to the left if we * are far enough to the right. */ if (count > 150) count = 0; return TRUE; } /* Scroll to the bottom of the buffer. */ static gboolean scroll_to_bottom (GtkTextView *textview) { GtkTextBuffer *buffer; GtkTextIter iter; GtkTextMark *mark; char *spaces; static int count; buffer = gtk_text_view_get_buffer (textview); /* Get end iterator */ gtk_text_buffer_get_end_iter (buffer, &iter); /* and insert some text at it, the iter will be revalidated * after insertion to point to the end of inserted text */ spaces = g_strnfill (count++, ' '); gtk_text_buffer_insert (buffer, &iter, "\n", -1); gtk_text_buffer_insert (buffer, &iter, spaces, -1); gtk_text_buffer_insert (buffer, &iter, "Scroll to bottom scroll to bottom scroll " "to bottom scroll to bottom", -1); g_free (spaces); /* Move the iterator to the beginning of line, so we don't scroll * in horizontal direction */ gtk_text_iter_set_line_offset (&iter, 0); /* and place the mark at iter. the mark will stay there after we * insert some text at the end because it has right gravity. */ mark = gtk_text_buffer_get_mark (buffer, "scroll"); gtk_text_buffer_move_mark (buffer, mark, &iter); /* Scroll the mark onscreen. */ gtk_text_view_scroll_mark_onscreen (textview, mark); /* Shift text back if we got enough to the right. */ if (count > 40) count = 0; return TRUE; } static guint setup_scroll (GtkTextView *textview, gboolean to_end) { GtkTextBuffer *buffer; GtkTextIter iter; buffer = gtk_text_view_get_buffer (textview); gtk_text_buffer_get_end_iter (buffer, &iter); if (to_end) { /* If we want to scroll to the end, including horizontal scrolling, * then we just create a mark with right gravity at the end of the * buffer. It will stay at the end unless explicitely moved with * gtk_text_buffer_move_mark. */ gtk_text_buffer_create_mark (buffer, "end", &iter, FALSE); /* Add scrolling timeout. */ return g_timeout_add (50, (GSourceFunc) scroll_to_end, textview); } else { /* If we want to scroll to the bottom, but not scroll horizontally, * then an end mark won't do the job. Just create a mark so we can * use it with gtk_text_view_scroll_mark_onscreen, we'll position it * explicitely when needed. Use left gravity so the mark stays where * we put it after inserting new text. */ gtk_text_buffer_create_mark (buffer, "scroll", &iter, TRUE); /* Add scrolling timeout. */ return g_timeout_add (100, (GSourceFunc) scroll_to_bottom, textview); } } static void remove_timeout (GtkWidget *window, gpointer timeout) { g_source_remove (GPOINTER_TO_UINT (timeout)); } static void create_text_view (GtkWidget *hbox, gboolean to_end) { GtkWidget *swindow; GtkWidget *textview; guint timeout; swindow = gtk_scrolled_window_new (NULL, NULL); gtk_box_pack_start (GTK_BOX (hbox), swindow, TRUE, TRUE, 0); textview = gtk_text_view_new (); gtk_container_add (GTK_CONTAINER (swindow), textview); timeout = setup_scroll (GTK_TEXT_VIEW (textview), to_end); /* Remove the timeout in destroy handler, so we don't try to * scroll destroyed widget. */ g_signal_connect (textview, "destroy", G_CALLBACK (remove_timeout), GUINT_TO_POINTER (timeout)); } GtkWidget * do_textscroll (GtkWidget *do_widget) { static GtkWidget *window = NULL; if (!window) { GtkWidget *hbox; window = gtk_window_new (GTK_WINDOW_TOPLEVEL); g_signal_connect (window, "destroy", G_CALLBACK (gtk_widget_destroyed), &window); gtk_window_set_default_size (GTK_WINDOW (window), 600, 400); hbox = gtk_hbox_new (TRUE, 6); gtk_container_add (GTK_CONTAINER (window), hbox); create_text_view (hbox, TRUE); create_text_view (hbox, FALSE); } if (!gtk_widget_get_visible (window)) gtk_widget_show_all (window); else gtk_widget_destroy (window); return window; }

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• Template inheritence c++

  - by Chris Condy

  I have made a template singleton class, I have also made a data structure that is templated. My question is; how do I make my templated data structure inherit from a singleton so you can only have one float type of this structure? I have tested both seperate and have found no problems. Code provided under... (That is the problem) template <class Type> class AbstractRManagers : public Singleton<AbstractRManagers<Type> > The problem is the code above doesn't work I get alot of errors. I cant get it to no matter what I do template a templated singleton class... I was asking for maybe advice or maybe if the code above is incorrect guidence? #ifndef SINGLETON_H #define SINGLETON_H template <class Type> class Singleton { public: virtual ~Singleton(); Singleton(); static Type* m_instance; }; template <class Type> Type* Singleton<Type>::m_instance = 0; #include "Singleton.cpp" #endif #ifndef SINGLETON_CPP #define SINGLETON_CPP #include "Singleton.h" template <class Type> Singleton<Type>::Singleton() { } template <class Type> Singleton<Type>::~Singleton() { } template <class Type> Type* Singleton<Type>::getInstance() { if(m_instance==nullptr) { m_instance = new Type; } return m_instance; } #endif #ifndef ABSTRACTRMANAGERS_H #define ABSTRACTRMANAGERS_H #include <vector> #include <map> #include <stack> #include "Singleton.h" template <class Type> class AbstractRManagers : public Singleton<AbstractRManagers<Type> > { public: virtual ~AbstractRManagers(); int insert(Type* type, std::string name); Type* remove(int i); Type* remove(std::string name); Type* get(int i); Type* getS(std::string name); int get(std::string name); int get(Type* i); bool check(std::string name); int resourceSize(); protected: private: std::vector<Type*> m_resources; std::map<std::string,int> m_map; std::stack<int> m_freePos; }; #include "AbstractRManagers.cpp" #endif #ifndef ABSTRACTRMANAGERS_CPP #define ABSTRACTRMANAGERS_CPP #include "AbstractRManagers.h" template <class Type> int AbstractRManagers<Type>::insert(Type* type, std::string name) { int i=0; if(!check(name)) { if(m_freePos.empty()) { m_resources.push_back(type); i = m_resources.size()-1; m_map[name] = i; } else { i = m_freePos.top(); m_freePos.pop(); m_resources[i] = type; m_map[name] = i; } } else i = -1; return i; } template <class Type> int AbstractRManagers<Type>::resourceSize() { return m_resources.size(); } template <class Type> bool AbstractRManagers<Type>::check(std::string name) { std::map<std::string,int>::iterator it; it = m_map.find(name); if(it==m_map.end()) return false; return true; } template <class Type> Type* AbstractRManagers<Type>::remove(std::string name) { Type* temp = m_resources[m_map[name]]; if(temp!=NULL) { std::map<std::string,int>::iterator it; it = m_map[name]; m_resources[m_map[name]] = NULL; m_freePos.push(m_map[name]); delete (*it).second; delete (*it).first; return temp; } return NULL; } template <class Type> Type* AbstractRManagers<Type>::remove(int i) { if((i < m_resources.size())&&(i > 0)) { Type* temp = m_resources[i]; m_resources[i] = NULL; m_freePos.push(i); std::map<std::string,int>::iterator it; for(it=m_map.begin();it!=m_map.end();it++) { if((*it).second == i) { delete (*it).second; delete (*it).first; return temp; } } return temp; } return NULL; } template <class Type> int AbstractRManagers<Type>::get(Type* i) { for(int i2=0;i2<m_resources.size();i2++) { if(i == m_resources[i2]) { return i2; } } return -1; } template <class Type> Type* AbstractRManagers<Type>::get(int i) { if((i < m_resources.size())&&(i >= 0)) { return m_resources[i]; } return NULL; } template <class Type> Type* AbstractRManagers<Type>::getS(std::string name) { return m_resources[m_map[name]]; } template <class Type> int AbstractRManagers<Type>::get(std::string name) { return m_map[name]; } template <class Type> AbstractRManagers<Type>::~AbstractRManagers() { } #endif #include "AbstractRManagers.h" struct b { float x; }; int main() { b* a = new b(); AbstractRManagers<b>::getInstance()->insert(a,"a"); return 0; } This program produces next errors when compiled : 1> main.cpp 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::stack<_Ty,_Container> &,const std::stack<_Ty,_Container> &)' : could not deduce template argument for 'const std::stack<_Ty,_Container> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\stack(166) : see declaration of 'std::operator <' 1> c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(124) : while compiling class template member function 'bool std::less<_Ty>::operator ()(const _Ty &,const _Ty &) const' 1> with 1> [ 1> _Ty=std::string 1> ] 1> c:\program files\microsoft visual studio 10.0\vc\include\map(71) : see reference to class template instantiation 'std::less<_Ty>' being compiled 1> with 1> [ 1> _Ty=std::string 1> ] 1> c:\program files\microsoft visual studio 10.0\vc\include\xtree(451) : see reference to class template instantiation 'std::_Tmap_traits<_Kty,_Ty,_Pr,_Alloc,_Mfl>' being compiled 1> with 1> [ 1> _Kty=std::string, 1> _Ty=int, 1> _Pr=std::less<std::string>, 1> _Alloc=std::allocator<std::pair<const std::string,int>>, 1> _Mfl=false 1> ] 1> c:\program files\microsoft visual studio 10.0\vc\include\xtree(520) : see reference to class template instantiation 'std::_Tree_nod<_Traits>' being compiled 1> with 1> [ 1> _Traits=std::_Tmap_traits<std::string,int,std::less<std::string>,std::allocator<std::pair<const std::string,int>>,false> 1> ] 1> c:\program files\microsoft visual studio 10.0\vc\include\xtree(659) : see reference to class template instantiation 'std::_Tree_val<_Traits>' being compiled 1> with 1> [ 1> _Traits=std::_Tmap_traits<std::string,int,std::less<std::string>,std::allocator<std::pair<const std::string,int>>,false> 1> ] 1> c:\program files\microsoft visual studio 10.0\vc\include\map(81) : see reference to class template instantiation 'std::_Tree<_Traits>' being compiled 1> with 1> [ 1> _Traits=std::_Tmap_traits<std::string,int,std::less<std::string>,std::allocator<std::pair<const std::string,int>>,false> 1> ] 1> c:\users\chris\desktop\311\ideas\idea1\idea1\abstractrmanagers.h(28) : see reference to class template instantiation 'std::map<_Kty,_Ty>' being compiled 1> with 1> [ 1> _Kty=std::string, 1> _Ty=int 1> ] 1> c:\users\chris\desktop\311\ideas\idea1\idea1\abstractrmanagers.h(30) : see reference to class template instantiation 'AbstractRManagers<Type>' being compiled 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::stack<_Ty,_Container> &,const std::stack<_Ty,_Container> &)' : could not deduce template argument for 'const std::stack<_Ty,_Container> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\stack(166) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::stack<_Ty,_Container> &,const std::stack<_Ty,_Container> &)' : could not deduce template argument for 'const std::stack<_Ty,_Container> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\stack(166) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::deque<_Ty,_Alloc> &,const std::deque<_Ty,_Alloc> &)' : could not deduce template argument for 'const std::deque<_Ty,_Alloc> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\deque(1725) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::deque<_Ty,_Alloc> &,const std::deque<_Ty,_Alloc> &)' : could not deduce template argument for 'const std::deque<_Ty,_Alloc> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\deque(1725) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::deque<_Ty,_Alloc> &,const std::deque<_Ty,_Alloc> &)' : could not deduce template argument for 'const std::deque<_Ty,_Alloc> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\deque(1725) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::_Tree<_Traits> &,const std::_Tree<_Traits> &)' : could not deduce template argument for 'const std::_Tree<_Traits> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\xtree(1885) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::_Tree<_Traits> &,const std::_Tree<_Traits> &)' : could not deduce template argument for 'const std::_Tree<_Traits> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\xtree(1885) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::_Tree<_Traits> &,const std::_Tree<_Traits> &)' : could not deduce template argument for 'const std::_Tree<_Traits> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\xtree(1885) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::vector<_Ty,_Ax> &,const std::vector<_Ty,_Ax> &)' : could not deduce template argument for 'const std::vector<_Ty,_Ax> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\vector(1502) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::vector<_Ty,_Ax> &,const std::vector<_Ty,_Ax> &)' : could not deduce template argument for 'const std::vector<_Ty,_Ax> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\vector(1502) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::vector<_Ty,_Ax> &,const std::vector<_Ty,_Ax> &)' : could not deduce template argument for 'const std::vector<_Ty,_Ax> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\vector(1502) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::unique_ptr<_Ty,_Dx> &,const std::unique_ptr<_Ty2,_Dx2> &)' : could not deduce template argument for 'const std::unique_ptr<_Ty,_Dx> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\memory(2582) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::unique_ptr<_Ty,_Dx> &,const std::unique_ptr<_Ty2,_Dx2> &)' : could not deduce template argument for 'const std::unique_ptr<_Ty,_Dx> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\memory(2582) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::unique_ptr<_Ty,_Dx> &,const std::unique_ptr<_Ty2,_Dx2> &)' : could not deduce template argument for 'const std::unique_ptr<_Ty,_Dx> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\memory(2582) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::reverse_iterator<_RanIt> &,const std::reverse_iterator<_RanIt2> &)' : could not deduce template argument for 'const std::reverse_iterator<_RanIt> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\xutility(1356) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::reverse_iterator<_RanIt> &,const std::reverse_iterator<_RanIt2> &)' : could not deduce template argument for 'const std::reverse_iterator<_RanIt> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\xutility(1356) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::reverse_iterator<_RanIt> &,const std::reverse_iterator<_RanIt2> &)' : could not deduce template argument for 'const std::reverse_iterator<_RanIt> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\xutility(1356) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::_Revranit<_RanIt,_Base> &,const std::_Revranit<_RanIt2,_Base2> &)' : could not deduce template argument for 'const std::_Revranit<_RanIt,_Base> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\xutility(1179) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::_Revranit<_RanIt,_Base> &,const std::_Revranit<_RanIt2,_Base2> &)' : could not deduce template argument for 'const std::_Revranit<_RanIt,_Base> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\xutility(1179) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::_Revranit<_RanIt,_Base> &,const std::_Revranit<_RanIt2,_Base2> &)' : could not deduce template argument for 'const std::_Revranit<_RanIt,_Base> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\xutility(1179) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::pair<_Ty1,_Ty2> &,const std::pair<_Ty1,_Ty2> &)' : could not deduce template argument for 'const std::pair<_Ty1,_Ty2> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\utility(318) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::pair<_Ty1,_Ty2> &,const std::pair<_Ty1,_Ty2> &)' : could not deduce template argument for 'const std::pair<_Ty1,_Ty2> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\utility(318) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::pair<_Ty1,_Ty2> &,const std::pair<_Ty1,_Ty2> &)' : could not deduce template argument for 'const std::pair<_Ty1,_Ty2> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\utility(318) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2676: binary '<' : 'const std::string' does not define this operator or a conversion to a type acceptable to the predefined operator ========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========

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• Sorting a file with 55K rows and varying Columns

  - by Prasad

  Hi I want to find a programmatic solution using C++. I have a 900 files each of 27MB size. (just to inform about the enormity ). Each file has 55K rows and Varying columns. But the header indicates the columns I want to sort the rows in an order w.r.t to a Column Value. I wrote the sorting algorithm for this (definitely my newbie attempts, you may say). This algorithm is working for few numbers, but fails for larger numbers. Here is the code for the same: basic functions I defined to use inside the main code: int getNumberOfColumns(const string& aline) { int ncols=0; istringstream ss(aline); string s1; while(ss>>s1) ncols++; return ncols; } vector<string> getWordsFromSentence(const string& aline) { vector<string>words; istringstream ss(aline); string tstr; while(ss>>tstr) words.push_back(tstr); return words; } bool findColumnName(vector<string> vs, const string& colName) { vector<string>::iterator it = find(vs.begin(), vs.end(), colName); if ( it != vs.end()) return true; else return false; } int getIndexForColumnName(vector<string> vs, const string& colName) { if ( !findColumnName(vs,colName) ) return -1; else { vector<string>::iterator it = find(vs.begin(), vs.end(), colName); return it - vs.begin(); } } ////////// I like the Recurssive functions - I tried to create a recursive function ///here. This worked for small values , say 20 rows. But for 55K - core dumps void sort2D(vector<string>vn, vector<string> &srt, int columnIndex) { vector<double> pVals; for ( int i = 0; i < vn.size(); i++) { vector<string>meancols = getWordsFromSentence(vn[i]); pVals.push_back(stringToDouble(meancols[columnIndex])); } srt.push_back(vn[max_element(pVals.begin(), pVals.end())-pVals.begin()]); if (vn.size() > 1 ) { vn.erase(vn.begin()+(max_element(pVals.begin(), pVals.end())-pVals.begin()) ); vector<string> vn2 = vn; //cout<<srt[srt.size() -1 ]<<endl; sort2D(vn2 , srt, columnIndex); } } Now the main code: for ( int i = 0; i < TissueNames.size() -1; i++) { for ( int j = i+1; j < TissueNames.size(); j++) { //string fname = path+"/gse7307_Female_rma"+TissueNames[i]+"_"+TissueNames[j]+".txt"; //string fname2 = sortpath2+"/gse7307_Female_rma"+TissueNames[i]+"_"+TissueNames[j]+"Sorted.txt"; string fname = path+"/gse7307_Male_rma"+TissueNames[i]+"_"+TissueNames[j]+".txt"; string fname2 = sortpath2+"/gse7307_Male_rma"+TissueNames[i]+"_"+TissueNames[j]+"4Columns.txt"; //vector<string>AllLinesInFile; BioInputStream fin(fname); string aline; getline(fin,aline); replace (aline.begin(), aline.end(), '"',' '); string headerline = aline; vector<string> header = getWordsFromSentence(aline); int pindex = getIndexForColumnName(header,"p-raw"); int xcindex = getIndexForColumnName(header,"xC"); int xeindex = getIndexForColumnName(header,"xE"); int prbindex = getIndexForColumnName(header,"X"); string newheaderline = "X\txC\txE\tp-raw"; BioOutputStream fsrt(fname2); fsrt<<newheaderline<<endl; int newpindex=3; while ( getline(fin, aline) ){ replace (aline.begin(), aline.end(), '"',' '); istringstream ss2(aline); string tstr; ss2>>tstr; tstr = ss2.str().substr(tstr.length()+1); vector<string> words = getWordsFromSentence(tstr); string values = words[prbindex]+"\t"+words[xcindex]+"\t"+words[xeindex]+"\t"+words[pindex]; AllLinesInFile.push_back(values); } vector<string>SortedLines; sort2D(AllLinesInFile, SortedLines,newpindex); for ( int si = 0; si < SortedLines.size(); si++) fsrt<<SortedLines[si]<<endl; cout<<"["<<i<<","<<j<<"] = "<<SortedLines.size()<<endl; } } can some one suggest me a better way of doing this? why it is failing for larger values. ? The primary function of interest for this query is Sort2D function. thanks for the time and patience. prasad.

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• Enum.values() vs EnumSet.allOf( ). Which one is more preferable?

  - by Alexander Pogrebnyak

  I looked under the hood for EnumSet.allOf and it looks very efficient, especially for enums with less than 64 values. Basically all sets share the single array of all possible enum values and the only other piece of information is a bitmask which in case of allOf is set in one swoop. On the other hand Enum.values() seems to be a bit of black magic. Moreover it returns an array, not a collection, so in many cases it must be decorated with Arrays.asList( ) to be usable in any place that expects collection. So, should EnumSet.allOf be more preferable to Enum.values? More specifically, which form of for iterator should be used: for ( final MyEnum val: MyEnum.values( ) ); or for ( final MyEnum val: EnumSet.allOf( MyEnum.values ) );

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• a more pythonic way to express conditionally bounded loop?

  - by msw

  I've got a loop that wants to execute to exhaustion or until some user specified limit is reached. I've got a construct that looks bad yet I can't seem to find a more elegant way to express it; is there one? def ello_bruce(limit=None): for i in xrange(10**5): if predicate(i): if not limit is None: limit -= 1 if limit <= 0: break def predicate(i): # lengthy computation return True Holy nesting! There has to be a better way. For purposes of a working example, xrange is used where I normally have an iterator of finite but unknown length (and predicate sometimes returns False).

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• Flex: Get an item from a AdvancedDataGrid given an index

  - by David Wolever

  I've got a subclass of AdvancedDataGrid showing a tree-like data structure. How can I, given the index returned by calculateDropIndex, get the item at that index? After reading through reams of code, it seems like the least terrible way is: var oldSelectedIndex:int = this.selectedIndex; var mouseOverIndex:int = this.calculateDropIndex(event); this.selectedItem = mouseOverIndex; var item:* = this.selectedItem; this.selectedIndex = oldSelectedIndex; The other option seems to be tinkering around with the iterator property... But, judging by the way I've seen it used, that will get pretty harry pretty quickly too. So, how can I get the item at a particular index in an advanced datagrid without going insane?

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• Common Pitfalls in Python

  - by Anurag Uniyal

  Today I was bitten again by "Mutable default arguments" after many years. I usually don't use mutable default arguments unless needed but I think with time I forgot about that, and today in the application I added tocElements=[] in a pdf generation function's argument list and now 'Table of Content' gets longer and longer after each invocation of "generate pdf" :) My question is what other things should I add to my list of things to MUST avoid? Mutable default arguments Import modules always same way e.g. from y import x and import x are different things, they are treated as different modules. Do not use range in place of lists because range() will become an iterator anyway, the following will fail: myIndexList = [0,1,3] isListSorted = myIndexList == range(3) # will fail in 3.0 isListSorted = myIndexList == list(range(3)) # will not same thing can be mistakenly done with xrange: `myIndexList == xrange(3)`. Catching multiple exceptions try: raise KeyError("hmm bug") except KeyError,TypeError: print TypeError It prints "hmm bug", though it is not a bug, it looks like we are catching exceptions of type KeyError,TypeError but instead we are catching KeyError only as variable TypeError, use this instead: try: raise KeyError("hmm bug") except (KeyError,TypeError): print TypeError

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• Iterating through nested dictionaries

  - by Framester

  I want to write an iterator for my 'toy' Trie implementation. Adding already works like this: class Trie: def __init__(self): self.root = dict() pass def add(self, string, value): global nops current_dict = self.root for letter in s: nops += 1 current_dict = current_dict.setdefault(letter, {}) current_dict = current_dict.setdefault('value', value) pass The output of the adding looks like that: trie = Trie() trie.add("hello",1) trie.add("world",2) trie.add("worlds",12) print trie.root {'h': {'e': {'l': {'l': {'o': {'value': 1}}}}}, 'w': {'o': {'r': {'l': {'d': {'s': {'value': 2}, 'value': 2}}}}}} I know, that I need a __iter__ and next method. def __iter__(self): self.root.__iter__() pass def next(self): print self.root.next() But AttributeError: 'dict' object has no attribute 'next'. How should I do it? [Update] In the perfect world I would like the output to be one dict with all the words/entries with their corresponding values.

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• A cross between std::multimap and std::vector?

  - by Milan Babuškov

  I'm looking for a STL container that works like std::multimap, but has constant access time to random n-th element. I need this because I have such structure in memory that is std::multimap for many reasons, but items stored in it have to be presented to the user in a listbox. Since amount of data is huge, I'm using list box with virtual items (i.e. list control polls for value at line X). As a workaround I'm currently using additional std::vector to store "indexes" into std::map, and I fill it like this: std::vector<MMap::data_type&> vec; for (MMap::iterator it = mmap.begin(); it != mmap.end(); ++it) vec.push_back((*it).second); But this is not very elegant solution. Is there some such containter?

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• Getting a char array from a vector<int>?

  - by Legend

  I am trying to pass a value from C++ to TCL. As I cannot pass pointers without the use of some complicated modules, I was thinking of converting a vector to a char array and then passing this as a null terminated string (which is relatively easy). I have a vector as follows: 12, 32, 42, 84 which I want to convert into something like: "12 32 42 48" The approach I am thinking of is to use an iterator to iterate through the vector and then convert each integer into its string representation and then add it into a char array (which is dynamically created initially by passing the size of the vector). Is this the right way or is there a function that already does this?

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• Could the assign function for containers possibly overflow?

  - by Kristo

  I ran into this question today and thought I should post it for the community's reference and/or opinions. The standard C++ containers vector, deque, list, and string provide an assign member function. There are two versions; I'm primarily interested in the one accepting an iterator range. The Josuttis book is a little ambiguous with its description. From p. 237... Assigns all elements of the range [beg,end); this is, is replaces all existing elements with copies of the elements of [beg,end). It doesn't say what happens if the size of the assignee container is different from the range being assigned. Does it truncate? Does it automagically expand? Is it undefined behavior?

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• no match for operator= using a std::vector

  - by Max

  I've got a class declared like this: class Level { private: std::vector<mapObject::MapObject> features; (...) }; and in one of its member functions I try to iterate through that vector like this: vector<mapObject::MapObject::iterator it; for(it=features.begin(); it<features.end(); it++) { /* loop code */ } This seems straightforward to me, but g++ gives me this error: src/Level.cpp:402: error: no match for ‘operator=’ in ‘it = ((const yarl::level::Level*)this)-yarl::level::Level::features.std::vector<_Tp, _Alloc::begin [with _Tp = yarl::mapObject::MapObject, _Alloc = std::allocator<yarl::mapObject::MapObject>]()’ /usr/include/c++/4.4/bits/stl_iterator.h:669: note: candidates are: __gnu_cxx::__normal_iterator<yarl::mapObject::MapObject*,std::vector & __gnu_cxx::__normal_iterator<yarl::mapObject::MapObject*,std::vector >::operator=(const __gnu_cxx::__normal_iterator<yarl::mapObject::MapObject*, ``std::vector<yarl::mapObject::MapObject, std::allocator<yarl::mapObject::MapObject> > >&) Anyone know why this is happening?

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• Issue with multipart upload in servlet on seam

  - by stacker

  I created a servlet wich works fine when deployed in a separate war file, but I intend to use it as part of a seam application. I use commons-fileupload but the iterator (see snippet) returns false (only when included in the seam-app). Any ideas? protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { try { String action = request.getParameter( "action" ); if ( ServletFileUpload.isMultipartContent( request ) ) { log.info( "MULTIPART" ); } ServletFileUpload upload = new ServletFileUpload(); FileItemIterator iter = upload.getItemIterator( request ); // --------- hasNext() returns false, only in seam ----------- while ( iter.hasNext() ) { ...... } Additional Info: I don't want to use the technique described here since the uploading client is curl. The HttpServletRequest is wrapped by org.jboss.seam.web.IdentityRequestWrapper Using the seam

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• Prototype.js: How can i return an array without all the methods Prototypes extends Array with?

  - by Morten

  Hi! Is there a way to return a new version of an array/hash that does not contain all the methods/functions that prototype extends the array object with? Example: var myArray = $A(); myArray['test'] = '1'; myArray['test2'] = '2'; var myVariableToPassToAjax = myArray; If I debug myVariableToPassToAjax it looks like this: Array ( [test] = 1 [test2] = 2 [each] = function each(iterator, context) { .......... .......... } ...and all the other extended array functions ); Is there a way to solve this? :-/ Morten

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• Help understanding some OpenGL stuff

  - by shinjuo

  I am working with some code to create a triangle that moves with arrow keys. I want to create a second object that moves independently. This is where I am having trouble, I have created the second actor, but cannot get it to move. There is too much code to post it all so I will just post a little and see if anyone can help at all. ogl_test.cpp #include "platform.h" #include "srt/scheduler.h" #include "model.h" #include "controller.h" #include "model_module.h" #include "graphics_module.h" class blob : public actor { public: blob(float x, float y) : actor(math::vector2f(x, y)) { } void render() { transform(); glBegin(GL_TRIANGLES); glVertex3f(0.25f, 0.0f, -5.0f); glVertex3f(-.5f, 0.25f, -5.0f); glVertex3f(-.5f, -0.25f, -5.0f); glEnd(); end_transform(); } void update(controller& c, float dt) { if (c.left_key) { rho += pi / 9.0f * dt; c.left_key = false; } if (c.right_key) { rho -= pi / 9.0f * dt; c.right_key = false; } if (c.up_key) { v += .1f * dt; c.up_key = false; } if (c.down_key) { v -= .1f * dt; if (v < 0.0) { v = 0.0; } c.down_key = false; } actor::update(c, dt); } }; class enemyOne : public actor { public: enemyOne(float x, float y) : actor(math::vector2f(x, y)) { } void render() { transform(); glBegin(GL_TRIANGLES); glVertex3f(0.25f, 0.0f, -5.0f); glVertex3f(-.5f, 0.25f, -5.0f); glVertex3f(-.5f, -0.25f, -5.0f); glEnd(); end_transform(); } void update(controller& c, float dt) { if (c.left_key) { rho += pi / 9.0f * dt; c.left_key = false; } if (c.right_key) { rho -= pi / 9.0f * dt; c.right_key = false; } if (c.up_key) { v += .1f * dt; c.up_key = false; } if (c.down_key) { v -= .1f * dt; if (v < 0.0) { v = 0.0; } c.down_key = false; } actor::update(c, dt); } }; int APIENTRY WinMain( HINSTANCE hInstance, HINSTANCE hPrevInstance, char* lpCmdLine, int nCmdShow ) { model m; controller control(m); srt::scheduler scheduler(33); srt::frame* model_frame = new srt::frame(scheduler.timer(), 0, 1, 2); srt::frame* render_frame = new srt::frame(scheduler.timer(), 1, 1, 2); model_frame->add(new model_module(m, control)); render_frame->add(new graphics_module(m)); scheduler.add(model_frame); scheduler.add(render_frame); blob* prime = new blob(0.0f, 0.0f); m.add(prime); m.set_prime(prime); enemyOne* primeTwo = new enemyOne(2.0f, 0.0f); m.add(primeTwo); m.set_prime(primeTwo); scheduler.start(); control.start(); return 0; } model.h #include <vector> #include "vec.h" const double pi = 3.14159265358979323; class controller; using math::vector2f; class actor { public: vector2f P; float theta; float v; float rho; actor(const vector2f& init_location) : P(init_location), rho(0.0), v(0.0), theta(0.0) { } virtual void render() = 0; virtual void update(controller&, float dt) { float v1 = v; float theta1 = theta + rho * dt; vector2f P1 = P + v1 * vector2f(cos(theta1), sin(theta1)); if (P1.x < -4.5f || P1.x > 4.5f) { P1.x = -P1.x; } if (P1.y < -4.5f || P1.y > 4.5f) { P1.y = -P1.y; } v = v1; theta = theta1; P = P1; } protected: void transform() { glPushMatrix(); glTranslatef(P.x, P.y, 0.0f); glRotatef(theta * 180.0f / pi, 0.0f, 0.0f, 1.0f); //Rotate about the z-axis } void end_transform() { glPopMatrix(); } }; class model { private: typedef std::vector<actor*> actor_vector; actor_vector actors; public: actor* _prime; model() { } void add(actor* a) { actors.push_back(a); } void set_prime(actor* a) { _prime = a; } void update(controller& control, float dt) { for (actor_vector::iterator i = actors.begin(); i != actors.end(); ++i) { (*i)->update(control, dt); } } void render() { for (actor_vector::iterator i = actors.begin(); i != actors.end(); ++i) { (*i)->render(); } } };

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• What is the right approach when using STL container for median calculation?

  - by sharkin

  Let's say I need to retrieve the median from a sequence of 1000000 random numeric values. If using anything but STL::list, I have no (built-in) way to sort sequence for median calculation. If using STL::list, I can't randomly access values to retrieve middle (median) of sorted sequence. Is it better to implement sorting myself and go with e.g. STL::vector, or is it better to use STL::list and use STL::list::iterator to for-loop-walk to the median value? The latter seems less overheadish, but also feels more ugly.. Or are there more and better alternatives for me?

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• Possible: Set Operations on Disparate Maps with Same Key Type?

  - by Catskul

  Let's say I have two maps: typedef int Id; std::map<Id, std::string> idToStringMap; std::map<Id, double> idToDoubleMap; And let's say I would like to do a set operation on the keys of the two maps. Is there an easier way to do this than to create a custom "inserter" iterator? such that I could do something like: std::set<Id> resultSet; set_difference( idToStringMap.begin(), idToStringMap.end(), idToDoubleMap.begin(), idToDoubleMap.end(), resultSet.begin() ); My experimentation results imply that it will be necessary to create a custom inserter and perhaps a custom key comparer to do this, but I want for some insight/shortcut before doing so.

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• Iterating backward

  - by MBennett

  Suppose I have a vector<int> myvec and I want to loop through all of the elements in reverse. I can think of a few ways of doing this: for (vector<int>::iterator it = myvec.end() - 1; it >= myvec.begin(); --it) { // do stuff here } for (vector<int>::reverse_iterator rit = myvec.rbegin(); rit != myvec.rend(); ++rit) { // do stuff here } for (int i = myvec.size() - 1; i >= 0; --i) { // do stuff here } So my question is when should I use each? Is there a difference? I know that the first one is dangerous because if I pass in an empty vector, then myvec.end() - 1 is undefined, but are there any other hazards or inefficiencies with this?

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• Flatten (an irregular) list of lists in Python

  - by telliott99

  Yes, I know this subject has been covered before (here, here, here, here), but AFAIK, all solutions save one choke on a list like this: L = [[[1, 2, 3], [4, 5]], 6] where the desired output is [1, 2, 3, 4, 5, 6] or perhaps even better, an iterator. The only solution I saw that works for an arbitrary nesting is from @Alabaster Codify here: def flatten(x): result = [] for el in x: if hasattr(el, "__iter__") and not isinstance(el, basestring): result.extend(flatten(el)) else: result.append(el) return result flatten(L) So to my question: is this the best model? Did I overlook something? Any problems?

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• How to transform a vector<int> into a string?

  - by Legend

  I am trying to pass a value from C++ to TCL. As I cannot pass pointers without the use of some complicated modules, I was thinking of converting a vector to a char array and then passing this as a null terminated string (which is relatively easy). I have a vector as follows: 12, 32, 42, 84 which I want to convert into something like: "12 32 42 48" The approach I am thinking of is to use an iterator to iterate through the vector and then convert each integer into its string representation and then add it into a char array (which is dynamically created initially by passing the size of the vector). Is this the right way or is there a function that already does this?

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