Thread: C++ arrays setting last value of one array to th first value of another

hi,

have noticed problem when using c++ on ubuntu laptop, title suggests, when using 2 arrays seems reason first value of 1 array being set thesecond value of array , not sure why, here example code of mine, please note root code have noticed happen normal c++ code:

of pseudo code, reading in ascii file containing 2 lists separated space in file, these read pair of vectors, couldnt find simple way used counter keep track of number looking at, put in correct vector.

root not seem vectors have move vectors simple arrays.
arrays used plot graph

code:

#include "riostream.h" #include<iostream> #include<fstream> #include"tvector.h" #include"tgraph.h" #include"tcanvas.h" #include"troot.h" #include"tpad.h" #include"taxis.h" #include"tmath.h" #include"th1f.h" #include"tframe.h" #include"tlegend.h"  int main()         {         double_t x;         double_t e[260], res[260];         vector<double_t> en;         vector<double_t> re;         int_t = 0;         ifstream file("q3data.txt");         while(file>>x)                 {                 if (i%2==0)                         {                         en.push_back(x);                         }                 if (i%2>0)                         {                         re.push_back(x);                         }                 i=i+1;                 }         for(int_t j=0;j<=260;j++)                  {                          e[j]=en[j];                          res[j]=re[j];                         cout<<e[j]<<" "<<res[j]<<endl;                 }         res[0]=re[0];  // if line not present reason res[0]=e[261]         cout<<res[0]<<endl;         cout<<e[0]<<endl;        tcanvas *c1 = new tcanvas("c1","1",200,10,700,500);         c1->setfillcolor(0);         c1->setgrid();  //th1f *hr = c1->drawframe(20,0,100,150);         tgraph *gr = new tgraph(260,e,res);          gr->setlinecolor(2);         gr->setlinewidth(4);         gr->setmarkercolor(4);         gr->setmarkerstyle(21);         gr->settitle("dsfdf");         gr->getxaxis()->settitle("df");         gr->getyaxis()->settitle("df");         gr->draw("acp");                 c1->saveas("3.1.pdf");          return 0;         }

i have indicated using comment string in code line seems sort out, no means proper solution.....

in regards particular code reason res[0] set equal e[261] or en[261] if res[0]=re[0] isnt added code shown above

have idea why happening?

bunch


edit should add running ubuntu 11.10 x64

res , e right next each other on stack. when access e[261], you're going past end of e array , res array. problem in loop:

code:

for(int_t j=0;j<=260;j++)

the last thing copy element 260. remember, however, arrays in c++ indexed 0, making elements of e , res 0-259, line should have j < 260 (not <=). e[260] same place in memory res[0].

code:

|  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |   ^ e[0]         ...        e[259] ^ | ^ res[0]        ...                                        ^ e[260]

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