How fill the array

Question

I want to write code for calculating some values and put these values in a 2-dimensional array. I have written very simple form of this problem.

This code gives me no output.

I want to have one for example m by n array or matrix with elements which are calculated by specific function.

#include "stdafx.h"
#include "iostream"
#include "cmath"
using namespace std;

double x;
int i,j;   
double A[10][10];
double M;

double function (double A,double x)
{
     for (i = 0; i = 9; ++i)
         for (j = 0; j = 9; ++j)
             M = 10 + x + A;
     return  M;
}

int _tmain(int argc, _TCHAR* argv[])
{
    double y;
    cin >> x;
    y = function(A[10][10], x);
    cout << y;

    return 0;
}

Perhaps the compiler objected to your indentation? Or your wanton mis-use of global variables. That aside, what output were you expecting? — David Heffernan
– David Heffernan, Commented Dec 23, 2013 at 19:55
OP wants to know how to initialize a matrix in a function... — Jarod42
– Jarod42, Commented Dec 23, 2013 at 20:19

Vlad from Moscow · Accepted Answer · 2013-12-23 19:57:49Z

2

This code has no any sense

{ for (i=0;i=9;++i) for (j=0;j=9;++j) M=10+x+A; return  M; }

You are assigning 9 to i and j in the loops. As 9 is not equal to 0 then these conditions i = 9 and j = 9will be always converted to true and the loops will be infinite. Also it is not clear what you are trying to calculate by using one more invalid expression M=10+x+A

answered Dec 23, 2013 at 19:57

Vlad from Moscow

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2 Comments

user3120411 Over a year ago

I mean I and j=10 ,I want to calculate elements of matrix or array.each element of matrix (M[i][j]) can be calculated by specific function.

Vlad from Moscow Over a year ago

Name M is not defined as an array by you. So I still do not understand what you are trying to do.

Dietmar Kühl · Accepted Answer · 2013-12-23 19:57:58Z

1

You use assignment = instead of equality == in your loop condition. Since 9 happens to convert to true your loops are infinite loops (BTW, you probably want to use i != 10 and likewise for j anyway).

answered Dec 23, 2013 at 19:57

Dietmar Kühl

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Comments

0xFADE · Accepted Answer · 2013-12-23 20:07:15Z

0

It looks like you intended to do:

 for (i = 0; i <= 9; ++i)
     for (j = 0; j <= 9; ++j)

You were missing the <. i < 10 would be the more standard usage.

answered Dec 23, 2013 at 20:07

0xFADE

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Comments

Jarod42 · Accepted Answer · 2013-12-23 20:15:33Z

0

Following may help you to understand how initialize array.

double createValueFromIndices(int x, int y)
{
    return 10. * x + y; // or any wanted value;
}

void initArray(double (&a)[10][10])
{
     for (int x = 0; x != 10; ++x) {
         for (int y = 0; y != 10; ++y) {
             a[x][y] = createValueFromIndices(x, y);
         }
     }
}


int main(int argc, char** argv)
{
    double a[10][10];

    initArray(a);

    return 0;
}

answered Dec 23, 2013 at 20:15

Jarod42

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1 Comment

Jarod42 Over a year ago

@user3120411: There is no output, but the array a will be initialized. So a[x][y] == 10. * x + y, for example a[4][2] == 42.

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