Function not changing contents of Vector

Jul 31, 2011 at 12:36am
Gene (38)
Is it because I need a pointer to it?
Jul 31, 2011 at 12:40am
Disch (13742)
Probably.

If you are passing by value, then you are actually changing a copy of the vector, and not the original vector itself.

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void by_ref(vector<int>& foo) // <- note the '&'
{
  foo.push_back(0);  // actually changes main_foo
}


void by_val(vector<int> foo) // <- note, no '&'
{
  foo.push_back(0);  // does not change main_foo
}

int main()
{
  vector<int> mainfoo;
  by_ref(mainfoo);  // change mainfoo;
  by_val(mainfoo);  // does not change mainfoo
}
Jul 31, 2011 at 12:42am
Gene (38)
I tried putting the ampersand in front as above, but then the program crashes
Jul 31, 2011 at 12:48am
Disch (13742)
then you're doing something wrong.

post some code and I'll see if I can spot the problem.
Jul 31, 2011 at 12:51am
Gene (38)
Ok, Its just too big to post all of it, so Ill post the Functions then the main

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#include <cstdlib>
#include <iostream>
#include <fstream>
#include <cstdio>
#include <vector>
#include <time.h>
#include <string>
#include <cctype>

using namespace std;

typedef pair<string,string> Pair_allele;

struct Person {
    int id;
    int generation;
    int life;
    bool alive;
    vector<Pair_allele> Genotypes;
    vector<string> Phenotypes;
    vector<string> Gene_List;
    Person(int i, int g) {
        id = i;
        generation = g;
        life = 3;
        alive = true;
    }
};

void clear_screen() {
    system("CLS");
    cout << "*============================*" << endl;
    cout << "|       Life Simulator       |" << endl;
    cout << "*============================*" << endl;
    cout << endl << "*=========================================================*" << endl << endl;
}

void Breed( vector<Person> list, vector<Pair_allele> Phenotypes, vector<Pair_allele> Genotypes, int g, vector<string> genes) {
    int size = list.size();
    for (int i = 0; i < size/2; i++) {
        int person_one = i;
        int person_two = rand() % (list.size()/2) + (list.size()/2);
        vector<Pair_allele> new_genotypes;
        vector<string> new_phenotypes;
        for (int j = 0; j < genes.size(); j++) {
            pair<string,string> Poss_one = (Pair_allele(list[person_one].Genotypes[j].first, list[person_two].Genotypes[j].first));
            pair<string,string> Poss_two = (Pair_allele(list[person_one].Genotypes[j].first, list[person_two].Genotypes[j].second));
            pair<string,string> Poss_three = (Pair_allele(list[person_one].Genotypes[j].second, list[person_two].Genotypes[j].second));
            int poss = rand() % 3;
            if (poss == 0) {
                new_genotypes.push_back(Pair_allele(Poss_one.first, Poss_one.second));
            }
            else if (poss == 1) {
                new_genotypes.push_back(Pair_allele(Poss_two.first, Poss_two.second));
            }
            else {
                new_genotypes.push_back(Pair_allele(Poss_three.first, Poss_three.second));
            }
            char c = new_genotypes[j].first[0];
            char d = new_genotypes[j].second[0];
            if (isupper(c)|| isupper(d) == true) {
                new_phenotypes.push_back(Phenotypes[j].first);
            }
            else {
                new_phenotypes.push_back(Phenotypes[j].second);
            }
        }
        list.push_back(Person(list.size()+1, g));
        for (int q = 0; q < genes.size(); q++) {
            list[list.size()-1].Genotypes.push_back( Pair_allele(new_genotypes[q].first, new_genotypes[q].second) );
            list[list.size()-1].Phenotypes.push_back( new_phenotypes[q] );
        }

    }
}
void Print_OverView(vector<Person> &P_List, vector<string> Genes, vector<Pair_allele> Pheno, vector<Pair_allele> Genotypes, int g) {
    vector<Pair_allele> permlist;
    for (int i = 0; i < Genes.size(); i++) {
        permlist.push_back(Pair_allele(Genotypes[i].first, Genotypes[i].first));
        permlist.push_back(Pair_allele(Genotypes[i].first, Genotypes[i].second));
        permlist.push_back(Pair_allele(Genotypes[i].second, Genotypes[i].second));
    }
    vector<int> numperms;
    for (int i = 0; i < permlist.size(); i++) {
        int tempa = 0;
        numperms.push_back(tempa);
    }
    vector<pair<int,int> > numpheno;
    for (int i = 0; i < Pheno.size(); i++) {
        pair<int,int> temppair;
        numpheno.push_back(temppair);
        numpheno[i].first = 0;
        numpheno[i].second = 0;
    }
    for (int i = 0; i < P_List.size(); i++) {
        for (int j = 0; j < Genes.size(); j++) {
            if (P_List[i].Gene_List[j] == Genes[j]) {
                if (P_List[i].Phenotypes[j] == Pheno[j].first) {
                    numpheno[j].first++;
                }
                else {
                    numpheno[j].second++;
                }
                if (P_List[i].Genotypes[j].first == permlist[j*3].first && P_List[i].Genotypes[j].second == permlist[j*3].second) {
                    numperms[j*3]++;
                }
                else if (P_List[i].Genotypes[j].first == permlist[j*3+1].first && P_List[i].Genotypes[j].second == permlist[j*3+1].second) {
                    numperms[j*3+1]++;
                }
                else if (P_List[i].Genotypes[j].first == permlist[j*3+2].first && P_List[i].Genotypes[j].second == permlist[j*3+2].second) {
                    numperms[j*3+2]++;
                }
            }
        }

    }
    system("CLS");
    cout << "*============================*" << endl;
    cout << "|       Life Simulator       |" << endl;
    cout << "*============================*" << endl;
    cout << endl << "*=========================================================*" << endl << endl;
    cout << "Generation " << g << endl;
    cout << "Population = " << P_List.size() << endl << endl;
    for (int i = 0; i < Genes.size(); i++) {
        cout << "Information About Gene " << Genes[i] << endl;
        cout << "   Number Of " << Pheno[i].first << " " << Genes[i] << " = " << numpheno[i].first << endl;
        cout << "   Number Of " << Pheno[i].second << " " << Genes[i] << " = " << numpheno[i].second << endl;
        cout << "   Number Of Allele Pair " << permlist[i*3].first << permlist[i*3].second << " = " << numperms[i*3] <<endl;
        cout << "   Number Of Allele Pair " << permlist[i*3+1].first << permlist[i*3+1].second << " = " << numperms[i*3+1] <<endl;
        cout << "   Number Of Allele Pair " << permlist[i*3+2].first << permlist[i*3+2].second << " = " << numperms[i*3+2] <<endl << endl;
    }
}


EDIT: Sorry, couldn't find any spoiler tags
Last edited on Jul 31, 2011 at 12:55am
Jul 31, 2011 at 1:28am
Zhuge (4664)
If the problem is in Breed() or Print_Overview(), then do as Disch suggested. If it generates a compiler error, post it.
Jul 31, 2011 at 1:33am
Gene (38)
If I put an ampersand as Disch said in the breed function, I dont get errors but when the program runs it crashes, same if I put it in the Breed and print overview function, if I just [put it in Print Overview, then it runs the same as without
Jul 31, 2011 at 2:15am
Disch (13742)
what line does it crash on?
Jul 31, 2011 at 2:18am
Gene (38)
not sure, Id imagine its in the breed function though
Jul 31, 2011 at 2:39am
Zhuge (4664)
Use a debugger and figure out where it's crashing. You might just find the error when doing that.
Jul 31, 2011 at 2:44am
Gene (38)
Right, the debugger found the error in Print OverView, in this line
if (P_List[i].Gene_List[j] == Genes[j]) {
Jul 31, 2011 at 2:46am
Gene (38)
Ok, I removed that line and its working now, must have been really tired to put that in for no reason
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