Questions on using the STL list sort method

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Questions on using the STL list sort method

 
0
  #1
Nov 7th, 2009
I am very new to using the STL list library. From what I have been reading here and other places on the web is that I have to create a compare function to use within the sort member function of list. The reason being that the list node's contain structures. I have to sort the list by a few different variables. Below is the class that controls my list. I am getting two errors.

Error 1) error C3867: 'Standings::compareForSort': function call missing argument list; use '&Standings::compareForSort' to create a pointer to member

Error 2) error C2660: 'std::list<_Ty>::sort' : function does not take 1 arguments

Any help here would be appreciated.

C++ Syntax (Toggle Plain Text) 
  1. #ifndef STANDINGS_H
  2. #define STANDINGS_H
  3.  
  4. #include <iostream>
  5. #include <list>
  6. #include <fstream>
  7. #include <iomanip>
  8.  
  9. using namespace std;
  10.  
  11. #define NAMELENGTH 20
  12.  
  13. struct Records
  14. {
  15. 	int totalWin;
  16. 	int totalLose;
  17. 	double winPercentage;
  18. 	double gamesBehind;
  19. 	int streakWin;
  20. 	int streakLose;
  21. 	int streakLength;
  22. 	int homeWin;
  23. 	int homeLose;
  24. 	int awayWin;
  25. 	int awayLose;
  26. 	int interWin;
  27. 	int interLose;
  28. 	int division;
  29. 	char teamName[NAMELENGTH];
  30. 	char streakType;
  31.  
  32. };
  33.  
  34.  
  35. class Standings
  36. {
  37. private:
  38. 	list<Records> recordsList;
  39. 	friend class Team;
  40. public:
  41. 	Standings();
  42. 	~Standings(){};
  43. 	void loadList();
  44. 	void saveList();
  45. 	void printStandings();
  46. 	bool compareForSort (Records&, Records&);
  47.  
  48. };
  49.  
  50. #endif
  51.  
  52. #include "standings.h"
  53.  
  54. Standings::Standings()
  55. {
  56.  
  57. }	
  58.  
  59.  
  60. void Standings::loadList(){
  61. 	//Create a variable of ifstream type names loadFile
  62. 	ifstream loadFile;                     
  63. 	//Open standings txt file
  64. 	loadFile.open("standings.txt");		 
  65. 	//Temporary object of struct type Record
  66. 	Records r;
  67.  
  68.  
  69. 	//Loop to take from file put into class 
  70. 	//and than put class into list
  71. 	while(!loadFile.eof()){
  72. 		loadFile >> r.teamName
  73. 			>> r.totalWin
  74. 			>> r.totalLose
  75. 			>> r.winPercentage
  76. 			>> r.gamesBehind
  77. 			>> r.streakWin
  78. 			>> r.streakLose
  79. 			>> r.streakType
  80. 			>> r.streakLength
  81. 			>> r.homeWin
  82. 			>> r.homeLose
  83. 			>> r.awayWin
  84. 			>> r.awayLose
  85. 			>> r.interWin
  86. 			>> r.interLose
  87. 			>> r.division;
  88.  
  89. 		//Checks to make sure its not the end of file.
  90. 		//If its not the end of the file it inserts 
  91. 		//the node at the end of the list
  92. 		if(!loadFile.eof())
  93. 			recordsList.push_back(r);
  94. 	}
  95. 	 //closing the text file
  96. 	loadFile.close(); 
  97. }
  98.  
  99. void Standings::saveList()
  100. {
  101. 	//Sorts the List before saving to txt
  102. 	recordsList.sort(compareForSort);
  103. 	//Create a variable of ofstream type names saveFile
  104. 	ofstream saveFile;                    
  105. 	//Open standings txt file
  106. 	saveFile.open("standings.txt");	
  107. 	//Create an iterator to keep place of the nodes saved
  108. 	list<Records>::iterator i;
  109.  
  110. 	//Loop through each node and save each member to that node
  111. 	for ( i=recordsList.begin(); i != recordsList.end(); ++i ) {
  112. 		saveFile << right << setw(13) << i->teamName << setw(4) << i->totalWin 
  113. 		<< setw(4) << i->totalLose << setw(7) << setprecision(3) << i->winPercentage 
  114. 		<< setw(6) << i->gamesBehind << setw(2) << i->streakWin 
  115. 		<< setw(2) << i->streakLose  << setw(2) << i->streakType 
  116. 		<< setw(2) << i->streakLength  << setw(3)<< i->homeWin 
  117. 		<< setw(3) << i->homeLose  << setw(3) << i->awayWin 
  118. 		<< setw(3) << i->awayLose  << setw(3)<< i->interWin 
  119. 		<< setw(3) << i->interLose  << setw(2) << i->division 
  120. 		<< endl;
  121. 	}
  122. //Flush and Close txt file
  123. 	saveFile.flush();
  124. 	saveFile.close();
  125.  
  126. }
  127.  
  128. void Standings::printStandings()
  129. {
  130. 	list<Records>::iterator i;
  131.  
  132. 	//Looping through each node and printing each variable of each node
  133. 	for ( i=recordsList.begin(); i != recordsList.end(); ++i ) 
  134. 	{
  135. 		cout  << right << setw(13) << i->teamName << setw(4) << i->totalWin 
  136. 			<< setw(4) << i->totalLose << right << setw(7) << i->winPercentage 
  137. 			<< right << setw(6) << i->gamesBehind << right << setw(2) << i->streakWin 
  138. 			<< right << setw(2) << i->streakLose << right << setw(2) << i->streakType 
  139. 			<< right << setw(2) << i->streakLength <<right << setw(3)<< i->homeWin 
  140. 			<< right << setw(3) << i->homeLose << right << setw(3) << i->awayWin 
  141. 			<< right << setw(3) << i->awayLose << right << setw(3)<< i->interWin 
  142. 			<< right << setw(3) << i->interLose << right << setw(2) << i->division 
  143. 			<< endl;
  144. 	}
  145. }
  146.  
  147.  
  148. bool Standings::compareForSort(Records& node1, Records& node2)
  149. {
  150. 	list<Records>::iterator i;
  151. 	for ( i=recordsList.begin(); i != recordsList.end(); ++i ) {
  152. 		if((node1.totalWin > node2.totalWin) && (node1.winPercentage > node2.winPercentage) && (node1.division < node2.division))
  153. 			return true;
  154. 		else 
  155. 		return false;
  156.  
  157. 	}
  158.  
  159. }
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  #2
Nov 7th, 2009
You cannot use std::sort with list (if that is what you intended to do)

list has its own sort. Here is an example : http://www.cplusplus.com/reference/stl/list/sort/ 
1) Prove that the area of a circle is pi*r^2, where "r" is the radius of the circle.
2) Problem 2[b]solved by : jonsca
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  #3
Nov 7th, 2009
Line 102 is where I call sort. recordsList is the name of my list, and compareForSort is the name of the function I wrote Though I am sure I need help with that function as well. Maybe I am trying to use std::sort but I thought recordsList.sort(compareForSort) was calling the list specific sort. Btw cplusplus is one of the places I did read about creating the compare function.
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-1
  #4
Nov 7th, 2009
shameless bump. Sorry but I could really use some help on this subject. Thank you ahead of time for any help received.
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  #5
Nov 7th, 2009
C++ Syntax (Toggle Plain Text) 
  1. recordsList.sort(compareForSort);

Try this :
C++ Syntax (Toggle Plain Text) 
  1. recordsList.sort(&Standings::compareForSort);
Last edited by firstPerson; Nov 7th, 2009 at 6:39 pm. 
1) Prove that the area of a circle is pi*r^2, where "r" is the radius of the circle.
2) Problem 2[b]solved by : jonsca
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  #6
Nov 7th, 2009
edit: sorry, my mistake, I mixed list with sort.
Last edited by Zjarek; Nov 7th, 2009 at 8:00 pm.
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  #7
Nov 7th, 2009
Ok now I am just getting

xutility(348) : error C2064: term does not evaluate to a function taking 2 arguments

I assume it is talking about the binary predicate function, but everywhere I read the binary predicate in other peoples example has two arguments.
Does it have to do with the fact that The nodes in the list are of struct Records while the list is being created in the standings class? Though the variables in Records are public so I dont see why that would be an issue. Here is the predicate function I have currently
C++ Syntax (Toggle Plain Text) 
  1. bool Standings::compareForSort(const Records& node1, const Records& node2)
  2. {
  3. return ((node1.totalWin > node2.totalWin) &&  (node1.winPercentage > node2.winPercentage) && (node1.division < node2.division));
  4.  
  5.  
  6. 	}
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  #8
Nov 8th, 2009
After doing more reading I found that some people use an overloaded < operator. So I attempted this and still getting loads of errors.

error C2676: binary '<' : 'Records' does not define this operator or a conversion to a type acceptable to the predefined operator

Here is my overloaded <
C++ Syntax (Toggle Plain Text) 
  1. bool Standings::operator <(const Records& node)
  2. {
  3. 	list<Records>::iterator i;
  4. 	//for ( i=recordsList.begin(); i != recordsList.end(); ++i ) {
  5. 		if ((i->totalWin > node.totalWin) && (i->winPercentage > node.winPercentage) && (i->division < node.division))
  6. 			 return true;
  7. 		else 
  8. 		return false;
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  #9
Nov 8th, 2009
I am going to continue putting the things I try because I dont want anyone to think I am not trying for myself. So I tried putting the overloaded < operator within my struct Records. No errors. The program is running fine. Except when it is time to sort its not sorting anything. So I guess it could be the logic or syntax within the operator
EDIT: Is there another way to sort a struct list by multiple variable values?

C++ Syntax (Toggle Plain Text) 
  1. bool operator <(const Records& node)
  2. {
  3. 	return ((totalWin > node.totalWin) && (winPercentage > node.winPercentage) && (division < node.division));
  4. }
Last edited by Afupi; Nov 8th, 2009 at 1:06 am.
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  #10
Nov 8th, 2009
>>xutility(348) : error C2064: term does not evaluate to a function taking 2 arguments

Which line is this from? 
1) Prove that the area of a circle is pi*r^2, where "r" is the radius of the circle.
2) Problem 2[b]solved by : jonsca
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