Question

Hey Guys...I'm trying to write a C program to add two matrices, but it seems that there's something wrong. It keeps giving these errors:

error: invalid types `int[int]' for array subscript
error: invalid types `int[int]' for array subscript
error: cannot convert `int (*)[10]' to `int*' for argument `1' to `int multi(int*, int*, int, int, int)'

I think the errors has something to do with the function declaration or function calls! what u think?!

Answer 1

Here's the program:

#include <stdio.h>


int sumat(int first[], int second[], int m, int n)
{
int arr[10][10];
for ( int c = 0 ; c < m ; c++ )
for ( int d = 0 ; d < n ; d++ )
arr[c][d] = first[c][d] + second[c][d];

printf("Sum of entered matrices:-\n");

for (int c = 0 ; c < m ; c++ )
for (int d = 0 ; d < n ; d++ )
printf("%d\t\n", arr[c][d]);

}

main()
{
int m, n, first[10][10], second[10][10];

printf("Enter the number of rows and columns of matrix ");
scanf("%d%d", &m, &n);
printf("Enter the elements of first & second matrix\n");

for (int c = 0 ; c < m ; c++ )
{
for (int d = 0 ; d < n ; d++ )
{
scanf("%d", &first[c][d]);
scanf("%d", &second[c][d]);
}
}
sumat(first, second, m, n);
}

Answer 2

Can you give us line numbers for those errors? Might help. :)

Answer 3

Alright, I just spent some time working on this...I haven't used c in a while so I'm a bit rusty. Here is what I did so far:

1. you need to define variables before the for loops
error: ‘for’ loop initial declarations are only allowed in C99 mode

2. sumat(int first[], int second[], int m, int n)
should be:
sumat(int first[][50], int second[][50], int m, int n)
beause you are trying to pass in arrays of arrays, you also need to specify the size (maximum)

3. I created a print matrix function for testing and to better break up the code, a function that is made for adding shouldn't be doing any printing. When printing you were adding a tab and a newline after each number (\t\n), there should just be a tab between and then the newline should only be once after each inner for loop (row)

Here is the new code, I renamed variables to better describe them:

\[#include <stdio.h>


int sumMatrix(int first[][50], int second[][50], int row, int col)
{
int y, x;
int arr[50][50];
for ( y = 0 ; y < row ; y++ )
for ( x = 0 ; x < col ; x++ )
arr[y][x] = first[y][x] + second[y][x];
}

printMatrix(int matrix[][50],int row, int col) {
int y, x;
for ( y = 0 ; y < row ; y++ ) {
for ( x = 0 ; x < col ; x++ ) {
printf("stored in:first[%d][%d]", y, x);
printf(":%d\t", matrix[y][x]);

}
printf("\n");
}
}

main()
{
//initialize variables
int x, y, row, col;

printf("Enter the number of rows and columns of matrix\nrows: ");
scanf("%d", &row);
printf("columns: ");
scanf("%d", &col);
int first[row][col], second[row][col];

printf("Enter the elements of first & second matrix\n");


for ( y = 0 ; y < row ; y++ )
{
for ( x = 0 ; x < col ; x++ )
{
scanf("%d", &first[y][x]);
printf("stored in:first[%d][%d]\n\n", y, x);
//scanf("%d", &second[y][x]);
}
}
//sumat(first, second, row, col) ;
printMatrix(first, row, col);
}\]

I'm just trying to properly pass the matrix into printMatrix and print it out but I'm getting this:
\[Enter the number of rows and columns of matrix
rows: 2
columns: 2
Enter the elements of first & second matrix
1
stored in:first[0][0]

2
stored in:first[0][1]

3
stored in:first[1][0]

4
stored in:first[1][1]

stored in:first[0][0]:1 stored in:first[0][1]:2
stored in:first[1][0]:-1037170512 stored in:first[1][1]:32767 \]
Only the entries in first[0] are being preserved, I'm probably making a stupid mistake. I'll put the ball back in your court now. Let me know what you come up with

Answer 4

first the function sunat(..) is int so u have to return a value it is not done here
2nd deceleration of c and d cannot be done in the for loop it is only possible in c++ u have to declare it before the clrscr() or starting of any codes