Sorting a vector of non-primitive data types (structs)
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Hi everyone, I'm attempting to write a program that takes command line arguments, reads data in from a file, and then appropriately searches for certain data or sorts the data for output based on the argument passed. I am having trouble figuring out how to actually sort the vectors according to the attributes. the struct is as follows:
struct Wizard { string FirstName; string LastName; int Grade; double WandWeight; };The datafile being read from simply has each property separated by a single whitespace character. The vector is declared simply as:vector(Wizard) wizVec;(NOTE: angle braces would not show up in preview, assume they take the place of the round braces in the vector declaration) Don't ask about the name of the struct, it's my prof's example! Any suggestions or solutions are appreciated and needed! Thanks in advance! -
Hi everyone, I'm attempting to write a program that takes command line arguments, reads data in from a file, and then appropriately searches for certain data or sorts the data for output based on the argument passed. I am having trouble figuring out how to actually sort the vectors according to the attributes. the struct is as follows:
struct Wizard { string FirstName; string LastName; int Grade; double WandWeight; };The datafile being read from simply has each property separated by a single whitespace character. The vector is declared simply as:vector(Wizard) wizVec;(NOTE: angle braces would not show up in preview, assume they take the place of the round braces in the vector declaration) Don't ask about the name of the struct, it's my prof's example! Any suggestions or solutions are appreciated and needed! Thanks in advance!To get < and > to show, you need to check 'Ignore HTML tags' below. You can write a function object that compares two Wizard objects, and pass that into the sort algorithm. Here[^] is an article on the subject.
Christian Graus - Microsoft MVP - C++ Metal Musings - Rex and my new metal blog "I am working on a project that will convert a FORTRAN code to corresponding C++ code.I am not aware of FORTRAN syntax" ( spotted in the C++/CLI forum )
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Hi everyone, I'm attempting to write a program that takes command line arguments, reads data in from a file, and then appropriately searches for certain data or sorts the data for output based on the argument passed. I am having trouble figuring out how to actually sort the vectors according to the attributes. the struct is as follows:
struct Wizard { string FirstName; string LastName; int Grade; double WandWeight; };The datafile being read from simply has each property separated by a single whitespace character. The vector is declared simply as:vector(Wizard) wizVec;(NOTE: angle braces would not show up in preview, assume they take the place of the round braces in the vector declaration) Don't ask about the name of the struct, it's my prof's example! Any suggestions or solutions are appreciated and needed! Thanks in advance!Use
std::sortto sort the vector. Add anoperator <for your struct to define the sort order or code a predicate function or functor and pass it tostd::sort.Steve
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Use
std::sortto sort the vector. Add anoperator <for your struct to define the sort order or code a predicate function or functor and pass it tostd::sort.Steve
Thanks for the article Christian, and the suggestion, Stephen. I will try to follow the instructions in the article. I appreciate the help, and the speedy replies :) Does this logic make sense in context? void SortVecAscending(vector &wizVector, string prop) { // Sort vector smallest to largest, according to prop(erty) bool compare_Wizards(const Wizard& a, const Wizard& b) { return a.prop < b.prop; } std::sort(wizVector.begin(), wizVector.end(), compare_Wizards); }
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Thanks for the article Christian, and the suggestion, Stephen. I will try to follow the instructions in the article. I appreciate the help, and the speedy replies :) Does this logic make sense in context? void SortVecAscending(vector &wizVector, string prop) { // Sort vector smallest to largest, according to prop(erty) bool compare_Wizards(const Wizard& a, const Wizard& b) { return a.prop < b.prop; } std::sort(wizVector.begin(), wizVector.end(), compare_Wizards); }
Yes, that looks like it should work.
Christian Graus - Microsoft MVP - C++ Metal Musings - Rex and my new metal blog "I am working on a project that will convert a FORTRAN code to corresponding C++ code.I am not aware of FORTRAN syntax" ( spotted in the C++/CLI forum )
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Hi everyone, I'm attempting to write a program that takes command line arguments, reads data in from a file, and then appropriately searches for certain data or sorts the data for output based on the argument passed. I am having trouble figuring out how to actually sort the vectors according to the attributes. the struct is as follows:
struct Wizard { string FirstName; string LastName; int Grade; double WandWeight; };The datafile being read from simply has each property separated by a single whitespace character. The vector is declared simply as:vector(Wizard) wizVec;(NOTE: angle braces would not show up in preview, assume they take the place of the round braces in the vector declaration) Don't ask about the name of the struct, it's my prof's example! Any suggestions or solutions are appreciated and needed! Thanks in advance!Thanks again for all your help, gentlemen. I got the sorting working with no more problems. However, now that I have moved on to the searching portion, I find that the way the project is designed, I have to search for values in the structs that are NOT strings. To refresh your memory: struct Wizard { string FirstName; string LastName; int Grade; double WandWeight; }; Is there any viable way to convert a string to an int, a string to a double, or vice versa? I have attempted to use static_cast() on the int and double values, and static_cast() / static_cast() on the string values, but the compiler didn't like those conversions. I have looked around, and there is nothing available to me without downloading someone's class and using it. Since this is a school project, I have a feeling that would be frowned upon. Any ideas? If any clarification is needed, simply ask.
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Yes, that looks like it should work.
Christian Graus - Microsoft MVP - C++ Metal Musings - Rex and my new metal blog "I am working on a project that will convert a FORTRAN code to corresponding C++ code.I am not aware of FORTRAN syntax" ( spotted in the C++/CLI forum )
C++ does not support local functions (functions in functions). You can have functors in function however.
Steve
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Thanks for the article Christian, and the suggestion, Stephen. I will try to follow the instructions in the article. I appreciate the help, and the speedy replies :) Does this logic make sense in context? void SortVecAscending(vector &wizVector, string prop) { // Sort vector smallest to largest, according to prop(erty) bool compare_Wizards(const Wizard& a, const Wizard& b) { return a.prop < b.prop; } std::sort(wizVector.begin(), wizVector.end(), compare_Wizards); }
C++ does not support local functions (functions in functions). You can have functors in function however.
Steve
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Thanks again for all your help, gentlemen. I got the sorting working with no more problems. However, now that I have moved on to the searching portion, I find that the way the project is designed, I have to search for values in the structs that are NOT strings. To refresh your memory: struct Wizard { string FirstName; string LastName; int Grade; double WandWeight; }; Is there any viable way to convert a string to an int, a string to a double, or vice versa? I have attempted to use static_cast() on the int and double values, and static_cast() / static_cast() on the string values, but the compiler didn't like those conversions. I have looked around, and there is nothing available to me without downloading someone's class and using it. Since this is a school project, I have a feeling that would be frowned upon. Any ideas? If any clarification is needed, simply ask.
There are multiple ways, here's one:
// CommandLine.cpp : Defines the entry point for the console application.
//
#include "StdAfx.h"
#include <iostream>
#include <string>
#include <sstream> // For 'istringstream'.
int main()
{
using namespace std;
string s = "1234";
int num;
istringstream ss(s);
ss >> num;
if (ss)
{
cout << "Number is " << num << endl;
}
return 0;
}And another:
// CommandLine.cpp : Defines the entry point for the console application.
//
#include "StdAfx.h"
#include <iostream>
#include <string>
#include <cstdlib>
int main()
{
using namespace std;
string s = "1234";
int num = atoi(s.c_str());
cout << "Number is " << num << endl;
return 0;
}The second method is easier but error handling is more difficult as if no valid conversion could be performed, a zero value is returned. Also, in the first version simply changing the type of the
numvariable will make the code work different types but the second version requires a distinct function for each type:atoionly works forints.Steve
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There are multiple ways, here's one:
// CommandLine.cpp : Defines the entry point for the console application.
//
#include "StdAfx.h"
#include <iostream>
#include <string>
#include <sstream> // For 'istringstream'.
int main()
{
using namespace std;
string s = "1234";
int num;
istringstream ss(s);
ss >> num;
if (ss)
{
cout << "Number is " << num << endl;
}
return 0;
}And another:
// CommandLine.cpp : Defines the entry point for the console application.
//
#include "StdAfx.h"
#include <iostream>
#include <string>
#include <cstdlib>
int main()
{
using namespace std;
string s = "1234";
int num = atoi(s.c_str());
cout << "Number is " << num << endl;
return 0;
}The second method is easier but error handling is more difficult as if no valid conversion could be performed, a zero value is returned. Also, in the first version simply changing the type of the
numvariable will make the code work different types but the second version requires a distinct function for each type:atoionly works forints.Steve
Thanks again! I ended up using the stringstream approach, as our prof is fanatical about us not using "pure" C functions. You guys are life savers! Regards, Bryan
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Thanks again! I ended up using the stringstream approach, as our prof is fanatical about us not using "pure" C functions. You guys are life savers! Regards, Bryan
Your professor is a wise man.
Steve
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Thanks again for all your help, gentlemen. I got the sorting working with no more problems. However, now that I have moved on to the searching portion, I find that the way the project is designed, I have to search for values in the structs that are NOT strings. To refresh your memory: struct Wizard { string FirstName; string LastName; int Grade; double WandWeight; }; Is there any viable way to convert a string to an int, a string to a double, or vice versa? I have attempted to use static_cast() on the int and double values, and static_cast() / static_cast() on the string values, but the compiler didn't like those conversions. I have looked around, and there is nothing available to me without downloading someone's class and using it. Since this is a school project, I have a feeling that would be frowned upon. Any ideas? If any clarification is needed, simply ask.
all_in_flames wrote:
Is there any viable way to convert a string to an int, a string to a double, or vice versa?
For future reference, we have a FAQ here :) -- 6.3 How can I change a number into its string representation, or vice versa? [^]
--Mike-- Visual C++ MVP :cool: LINKS~! Ericahist | PimpFish | CP SearchBar v3.0 | C++ Forum FAQ Ford, what's this fish doing in my ear?
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all_in_flames wrote:
Is there any viable way to convert a string to an int, a string to a double, or vice versa?
For future reference, we have a FAQ here :) -- 6.3 How can I change a number into its string representation, or vice versa? [^]
--Mike-- Visual C++ MVP :cool: LINKS~! Ericahist | PimpFish | CP SearchBar v3.0 | C++ Forum FAQ Ford, what's this fish doing in my ear?
Thanks for the info, Mike! I'm a codeproject n00b, but I get the newsletter! ;)