problem with arrays and my minimum function

[jzackt]

Im trying to learn how to use arrays in C and I'm having some trouble. I think my main problem is understanding the use of pointers. I'm just trying to take the min grade in the text file. Here is my source code:

#include <stdio.h>
#include <math.h>
#include <stdlib.h>
#define MAX_G 60
#define MAX_N 20


main()
{

FILE* fipoint;
double StudentGrades[20][3];
char StudentNames[20][9];
int x = 0,studentnum1;
void minimum(char names_array, double grades_array);


fipoint=fopen("grades.txt","r");

if(fipoint==NULL)
{
printf("Cannot open file!\n");
}
else
{
while(fscanf(fipoint,"%s",&StudentNames[x])>0)
{
fscanf(fipoint,"%lf", &StudentGrades[x][0]);
fscanf(fipoint,"%lf", &StudentGrades[x][1]);
fscanf(fipoint,"%lf", &StudentGrades[x][2]);

printf("%s %lf %lf %lf\n", StudentNames[x], StudentGrades[x][0],
StudentGrades[x][1], StudentGrades[x][2]);

x++;
}

fclose(fipoint);

}



minimum((char)StudentNames,(double)StudentGrades);






system("pause");

}
/*****************************Minimum Function*********************************/
void minimum(char names_array, double grades_array)
{
int row=0,colmn=0,minrow=0;

int count=0;
double mini=0;


while(row<20){
if (grades_array[row][colmn]<=grades_array[row][colmn+1]){
mini==grades_array[row][colmn];
colmn++;

}

else {
mini==grades_array[row][colmn+1];
colmn++;
}

if(colmn==1){
row++;
colmn=0;
}

}

printf("Student %d had the lowest grade of %lf\n\n",minrow+1,mini);

}

This what my grades.txt file looks like:
Student1 77 68 86
Student2 50 60 35
Student3 45 87 90
Student4 60 87 90
Student5 34 56 4
Student6 1 2 3
Student7 67 75 81
Student8 23 45 90
Student9 1 50 100
Student10 34 65 86
Student11 38 98 78
Student12 67 54 97
Student13 99 98 87
Student14 17 71 7
Student15 64 86 87
Student16 56 78 65
Student17 23 45 76
Student18 69 96 87
Student19 45 78 88
Student20 80 81 90

[Gumbercules]

your minimum function's parameters are not arrays, but just a char and a double. You can't truly pass an array, but only a pointer to an array. You'll also need the length, or the ending pointer.

[jzackt]

can you give me an example of how you would do it please. thanks

[Gumbercules]

I must admit, I'm a bit confused with your multidimential arrays, so I'll do something simple. These are just two different ways to do the same thing.

#include <iostream>
using namespace std;
void average1(double *grades, int length) {
double total = 0;
    for (int i = 0; i < length; ++i)
        total += grades[i];  // pointers to an array can be indexed just as arrays
cout << "average = " << (total / length) << endl;
}
void average2(double *begin, double *end) {
double total = 0;
    for (double *p = begin; p != end; ++p)
        total += *p;  // pointers to an array can be indexed just as arrays
cout << "average = " << (total / (end - begin)) << endl; // (end - begin) might be bad, maybe someone can tell me if it should be avoided.
}
int main() {
     double gradesArray[] = {80.0, 60.0, 70.0, 75.0, 80.0};
     average1(gradesArray, 5);
     average2(gradesArray, gradesArray + 5);
}

notice that pointers can be referenced like arrays with [], and arrays can be passed as pointers.

[jzackt]

thanks...hopefully this will help