c++ making an array of zeros?

wankel · 2009-05-22 21:25:42

Hi, Im trying to make an array that will be filled with data later, but I keep getting the following error when compiling:

error: incompatible types in assignment of of 'int*' to 'int[10]'

Im using the following line:

int counter[10]={0}

What needs to be changed? I read everywhere online and this is how they recommend doing it.

deej · 2009-05-22 21:30:40

Try:

int counter[10];

This will initialize your array.

If you want it filled with zeroes:

int counter[] = { 0,0,0,0,0,0,0,0,0,0};

or:

int counter[10] = { 0,0,0,0,0,0,0,0,0,0};

Deej

Themaister · 2009-05-22 22:32:29

If there's, let's say an array of 1000, and you want it all initialized as zeros, is this the fastest way to do it?

int counter[1000];
for (int a = 0; a < 1000; a++) counter[a] = 0;

?

jsgt · 2009-05-22 22:55:37

You could, but a better alternative is to use memset: memset( counter, 0, sizeof( counter ) )

kumyco · 2009-05-23 01:45:48

you can do

int a[1000] = {0};

the rest will be init to 0

abesto · 2009-05-23 09:39:18

This isn't strictly an answer to your question, but as we're talking about C++, why not use a vector? (or even a list if it's one of those situations)

#include <vector>
...
vector<int> counter(10, 0);  // A vector of type int, size 10, each element is 0

Same thing for lists, just s/vector/list/g

kakTuZ · 2009-05-23 13:40:49

or use

int array[10];
std::fill( array, array+10, 0);

But using std::vector is a much better alternative (see previous post).

Last edited by kakTuZ (2009-05-23 13:42:02)

Lexion · 2009-05-23 22:17:08

memset is better than fill, as it is more economic with data and CPU.

wankel · 2009-05-27 04:26:08

Hey guys, I tried all the suggestions provided and they all give me different kind of errors =/

Heres my code, "counter" is the array im trying to make that has a size of "height". can anyone see a reason why Id be getting errors trying to do this?

#include <stdio.h>
#include "CImg.h"
#include <vector>

using namespace cimg_library;


//main program
int main()
{
CImg<unsigned char> img("xray.jpg");

const unsigned int width = img.dimx();
const unsigned int height = img.dimy();

//converts the image to black and white
img.RGBtoYCbCr().channel(0).resize(-100,-100,1,3).RGBtoLUT(CImg<>(2,1,1,3).fill(0.0f,255.0f),false); 

//displays image
CImgDisplay display(img,"Black and White");
while (!display.is_closed)
display.wait();


printf("The height of the image is %d\n",height);
printf("The width of the image is %d\n",width);

//counter array
int counter[10];
std:fill( counter, counter+10, 0);

for (int i=0;i<width;i++)
    for (int j=0;j<height;j++)
        for (int k=0;k<3;k++)
            if (img(i,j,0,k)=0) {
            counter=counter+1;
            }    

printf("%d",counter);
return 0;
}

Allan · 2009-05-27 04:31:38

You start out treating counter as an array of length "height" - you probably want to use height not ten....:

//counter array
int counter[10];
std:fill( counter, counter+10, 0);

Then treat is like an int

counter=counter+1;

I guess you want:

coutner[j] += 1

An again:

printf("%d",counter);

You probably want to loop an print out each position.

the_isz · 2009-05-27 05:49:30

Also, are you sure this condition is what you want?

if (img(i,j,0,k)=0)

This would assign the value of img at coordinate i,j,0,k the value 0 and return true every time that assignment
was successful (which should be always, except if you encounter some kind of index error or something).

You probably mean this:

if (img(i,j,0,k)==0)

Tip from my side: Get used to write constants first when doing comparisons. That way, the compiler will complain
if you forget a '=':

if (0=img(i,j,0,k))  // yields error
if (img(i,j,0,k)=0)  // compiles ok, but probably not what you expect
if (0==img(i,j,0,k)) // what you expect, more typing-error secure

I know, it takes time to get used to, but it helps avoiding such nasty mistakes

mfisher_ix · 2009-05-29 03:43:24

wankel wrote:

int counter[10]={0}

Wankel, your original code should work (assuming the statement was correctly ended with a semicolon). A few questions:

- What compiler are you using, and what command are you using to compile?

- Are you sure the line number for the error refers to this statement?

wankel · 2009-05-31 22:34:12

mfisher_ix, this is the command im using to compile:

g++ -o beta.exe beta.cpp -O2 -L/usr/X11R6/lib -lm -lpthread -lX11

and im fairly certain thats the line where the error refers to

the_isz, thanks for the tips, ill definitely implement them

allan, thanks for the help! using 10 instead of height was just to test it out, in the end i want the counter to have "height" rows

Arch Linux

#1 2009-05-22 21:25:42

c++ making an array of zeros?

#2 2009-05-22 21:30:40

Re: c++ making an array of zeros?

#3 2009-05-22 22:32:29

Re: c++ making an array of zeros?

#4 2009-05-22 22:55:37

Re: c++ making an array of zeros?

#5 2009-05-23 01:45:48

Re: c++ making an array of zeros?

#6 2009-05-23 09:39:18

Re: c++ making an array of zeros?

#7 2009-05-23 13:40:49

Re: c++ making an array of zeros?

#8 2009-05-23 22:17:08

Re: c++ making an array of zeros?

#9 2009-05-27 04:26:08

Re: c++ making an array of zeros?

#10 2009-05-27 04:31:38

Re: c++ making an array of zeros?

#11 2009-05-27 05:49:30

Re: c++ making an array of zeros?

#12 2009-05-29 03:43:24

Re: c++ making an array of zeros?

#13 2009-05-31 22:34:12

Re: c++ making an array of zeros?

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