Thread: having some trouble with making a simple function,help please

Code:

#include <stdio.h>
#include <stdlib.h>


void generate(int *number,int *number_of_words,char words[30][6]);


int main()
{     int number,number_of_words;
     char words[30][6];
    
    generate(&number,&number_of_words,&words[30][6]);
    
    printf("\n\n word is %c%c%c%c%c",words[number][1],words[number][2],words[number][3],words[number][4],words[number][5]);


return 0;
}
void generate(int *number,int *number_of_words,char words[30][6])
{
 
     
    int i,j;
    FILE*text;
    text=fopen("words.txt","r");
    srand( (unsigned) time (NULL) );
    *number=rand()%30;
    
     
     
     if (text == NULL)
     {
         exit(1);
     }
    
    fscanf(text,"%i",*number_of_words);
    
    for (i=0;i<*number_of_words;i++)
    
    {    for(j = 0; j <6 ; j++)
        {
          
        fscanf(text,"%c",words[i][j]);
        
        
        }
        
    
        
    }    
    
        fclose(text);
        
}

> char words[30][6];
If this is your array.

Then the function should be declared as (and the same in the implementation)
void generate(int *number,int *number_of_words,char words[30][6]);

And called as
generate(&number,&number_of_words,words);


> fscanf(text,"%c",*words[i][j]);
Do exactly what you would do, if the array was in scope.
ie
fscanf(text,"%c",&words[i][j]);

Inside the generate() function, with words a pointer to int, words[i] is a char. words[i][j] is meaningless, which is why your compiler is complaining bitterly. Prefixing words[i][j] with an asterix is just insane (but fortunately the compiler will keep complaining).

The bigger problem is in how you're calling the function &words[30][6] is the address of an int that is past the end of the words array. Since you're then (not withstanding the errors I have pointed out inside the generate() function) treating that address as the start of a 2D array, your code will tromp random areas of memory.



More generally, when a compiler complains, the onus is on you to reason out WHY it is complaining, rather than just randomly hacking code in the hope things will work. Your biggest mistake is that you are electing to use the hacking approach. If my response seems unhelpful, it is because your hacking approach makes it pointless to be more helpful than I am.

Code:

#include <stdio.h>
#include <stdlib.h>


void generate(int *number,int *number_of_words,char words[30][6]);


int main()
{     int number,number_of_words;
     char words[30][6];
    
    generate(&number,&number_of_words,words);
    
    printf("\n\n word is %c%c%c%c%c",words[number][1],words[number][2],words[number][3],words[number][4],words[number][5]);


return 0;
}
void generate(int *number,int *number_of_words,char words[30][6])
{
 
     
    int i,j;
    FILE*text;
    text=fopen("words.txt","r");
    srand( (unsigned) time (NULL) );
    *number=rand()%30;
    
     
     
     if (text == NULL)
     {
         exit(1);
     }
    
    fscanf(text,"%i",number_of_words);
    
    for (i=0;i<*number_of_words;i++)
    
    {    for(j = 0; j <6 ; j++)
        {
          
        fscanf(text,"%c",&words[i][j]);
        
        
        }
        
    
        
    }    
    
        fclose(text);
        
}

See?
Compiles without error here.

Whether it runs or not is another matter.

> could someone please explain to me why the program wont work,the compiler builds it without error but it doesnt work
And what do you mean "doesn't work"?

Does it crash?
If it doesn't crash, what output do you see, and how is that different from what you expect?

Remember, we don't have your words.txt file to even begin to guess how you're reading it wrong.

But given that you're using %c to read the file, you need to understand that file format is critical. If you're out by even 1 character, then the program just won't work as expected.

Code:

for (i=0;i<*number_of_words;i++)

"number_of_words" is not initialised.

Originally Posted by africanwizz

the fscanf function gives a value of 30 to "number_of_words"

Whoops - So it does!

Check to see if it is 30.