Char array display error...

I have a problem displaying a string which is a part of a 2-dimensional array.
Here's my code...
- As long as I don't enter 8 for "Other" everything is displayed ok, but as soon as i choose 8 when running the program, the first item of the array, i.e. "Bread" is always replaced with some gibberish. The rest of the array is displayed fine... What am i doing wrong?
I thought maybe it has something to do with the minus in the Sub-total, which follows the "other" option... Any help is much appreciated.

Code:

---

#include <stdio.h>

int main ( ) {

char item[11][20] = {" Bread", " Butter", " Confectionary",
                                " Fruit", " Meat", " Milk", " Vegetables",
                                " Other", " Sub-total", "Total", "Quit"};
int i;
int choice;
float bread, butter, conf, fruit, meat, milk, veg, other;
float sum, tendered, change;
float subtotals[7];

bread = 0;
butter = 0;
conf = 0;
fruit = 0;
meat = 0;
milk = 0;
veg = 0;
other = 0;

choice = 0;
tendered = 0.0;

while (choice != 11) {
        printf("\n Enter your choice:\n");
        for (i = 0; i < 11; i++)
        {
                printf("\t%d. %s\n", (i + 1), item[i]);
        }
        printf("\t\t--> ");
        scanf("%d", &choice);

        switch (choice){
                case 1:
                        printf(" Price:\t\t");
                        scanf("%f", &subtotals[0]);
                        bread += subtotals[0];
                        break;
                case 2:
                        printf(" Price:\t\t");
                        scanf("%f", &subtotals[1]);
                        butter += subtotals[1];
                        break;
                case 3:
                        printf(" Price:\t\t");
                        scanf("%f", &subtotals[2]);
                        conf += conf + subtotals[2];
                        break;
                case 4:
                        printf(" Price:\t\t");
                        scanf("%f", &subtotals[3]);
                        fruit += subtotals[3];
                        break;
                case 5:
                        printf(" Price:\t\t");
                        scanf("%f", &subtotals[4]);
                        meat += subtotals[4];
                        break;
                case 6:
                        printf(" Price:\t\t");
                        scanf("%f", &subtotals[5]);
                        milk += subtotals[5];
                        break;
                case 7:
                        printf(" Price:\t\t");
                        scanf("%f", &subtotals[6]);
                        veg += subtotals[6];
                        break;
                case 8:
                        printf(" Price:\t\t");
                        scanf("%f", &subtotals[7]);
                        other += subtotals[7];
                        break;
                case 9:
                        if (bread > 0){
                                printf("\n%s:\t\t\t%9.2f", item[0], bread);
                        }
                        if (butter > 0){
                                printf("\n%s:\t\t%9.2f", item[1], butter);
                        }
                        if (conf > 0){
                                printf("\n%s:\t\t%9.2f", item[2], conf);
                        }
                        if (fruit > 0){
                                printf("\n%s:\t\t\t%9.2f", item[3], fruit);
                        }
                        if (meat > 0){
                                printf("\n%s:\t\t\t%9.2f", item[4], meat);
                        }
                        if (milk > 0){
                                printf("\n%s:\t\t\t%9.2f", item[5], milk);
                        }
                        if (veg > 0){
                                printf("\n%s:\t\t%9.2f", item[6], veg);
                        }
                        if (other > 0){
                                printf("\n%s:\t\t\t%9.2f", item[7], other);
                        }
                        sum = bread + butter + conf + fruit + meat + milk + veg + other;
                        printf("\n----------------------------------\n");
                        printf(" Total:\t\t\t%9.2f\n", sum);
                        printf("----------------------------------\n");
                        break;
                case 10:
                        if (bread > 0){
                                printf("\n%s:\t\t\t%9.2f", item[0], bread);
                        }
                        if (butter > 0){
                                printf("\n%s:\t\t%9.2f", item[1], butter);
                        }
                        if (conf > 0){
                                printf("\n%s:\t\t%9.2f", item[2], conf);
                        }
                        if (fruit > 0){
                                printf("\n%s:\t\t\t%9.2f", item[3], fruit);
                        }
                        if (meat > 0){
                                printf("\n%s:\t\t\t%9.2f", item[4], meat);
                        }
                        if (milk > 0){
                                printf("\n%s:\t\t\t%9.2f", item[5], milk);
                        }
                        if (veg > 0){
                                printf("\n%s:\t\t%9.2f", item[6], veg);
                        }
                        if (other > 0){
                                printf("\n%s:\t\t\t%9.2f", item[7], other);
                        }
                        sum = bread + butter + conf + fruit + meat + milk + veg + other;
                        printf("\n-----------------------------------\n");
                        printf(" Total:\t\t\t%9.2f\n", sum);
                        printf("-----------------------------------\n");
                        printf(" Tendered:\t\t");
                        scanf("%f\n", &tendered);
                        change = tendered - sum;
                        printf(" Change:\t\t%9.2f\n", change);
                        break;
        }
}

}

---

How many subtotals do you have, and what is the biggest index you use?

--
Mats

I got only 1 sub-total, but it loops while user enters anything but 11 (which exits the program). Biggest index? If i understand you correctly, its 11 to quit.

No, your array subtotals, which is the highest index you use, and how large is the array itself?

--
Mats

Code:

---

conf += conf + subtotals[2];

---

Is that right?

Code:

---

scanf("%f\n", &tendered);

---

Don't think you mean that to be there.

I know whats the problem now... I have 8 items in the list, but only 7 subtotals i.e. subtotal[7]...

btw, this is my first ever assignment. I've been asked to use arrays, loops and if/switch statements...
From a pro point of view, does this code look OK? Are there any simpler ways of approaching certain parts of the code? Any advice is much appreciated :)

A minor suggestion:

The whole switch statement can be replace with:

Code:

---

    printf(" Price:\t\t");
    scanf("%f", &subtotals[choice]);
    bread += subtotals[choice];
    break;

---

Cause that's all it's doing. Using choice as an index.

Oops, i replied seconds too late... Thank you guys...
hk_mp5kpdw, i was doing it the simpler way and then started editing the code to "optimize" it a bit, if you like... Must have missed that :)
IceDane: Great, will work on it now :D

You are completely unnecessarily using subtotals as an array - you are only ever using one item at any given time, so you could just use a simple variable.

I would use a do - while() loop rather than a while() loop, because you are always wanting to do at least ONE choice.

I would probably also use an array instead of simple variables for the sum of each product category, e.g. instead of "bread", use prodCost[choice-1]. That way, you could have all the first 7 choices as one case. Then you could use a loop for cases 9 and 10, instead of a lot of repeated code that is almost the same but not quite.

--
Mats

Quote:

---

Originally Posted by Karpaty

I know whats the problem now... I have 8 items in the list, but only 7 subtotals i.e. subtotal[7]...

btw, this is my first ever assignment. I've been asked to use arrays, loops and if/switch statements...
From a pro point of view, does this code look OK? Are there any simpler ways of approaching certain parts of the code? Any advice is much appreciated :)

---

There is a lot of duplicated code there, IceDane's suggestion points to a better way although it won't work exactly as he's put it. How I'd do it (untested):

Code:

---

char item[11][20] = {" Bread", " Butter", " Confectionary",
                                " Fruit", " Meat", " Milk", " Vegetables",
                                " Other", " Sub-total", "Total", "Quit"};
int i;
int choice = 0;
float cost;
float sum, tendered, change;
float subtotals[8] = { 0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 0.0f };

while (choice != 11) {
    printf("\n Enter your choice:\n");
    for (i = 0; i < 11; i++)
    {
        printf("\t&#37;d. %s\n", (i + 1), item[i]);
    }
    printf("\t\t--> ");
    scanf("%d", &choice);

    if( choice > 0 && choice < 9 )
    {
        printf(" Price:\t\t");
        scanf("%f", &cost);
        subtotals[choice-1] += cost;
    }
    else if( choice == 9 )
    {
        for( i = 0; i < 8; ++i )
        {
            sum = 0;
            if( subtotals[i] > 0 )
                printf("\n%s:\t\t\t%9.2f",item[i],subtotals[i]);
            sum += subtotals[i];
        }
        printf("\n----------------------------------\n");
        printf(" Total:\t\t\t%9.2f\n", sum);
        printf("----------------------------------\n");
    }
    else if( choice == 10 )
    {
        for( i = 0; i < 8; ++i )
        {
            sum = 0;
            if( subtotals[i] > 0 )
                printf("\n%s:\t\t\t%9.2f",item[i],subtotals[i]);
            sum += subtotals[i];
        }
        printf("\n----------------------------------\n");
        printf(" Total:\t\t\t%9.2f\n", sum);
        printf("----------------------------------\n");
        printf(" Tendered:\t\t");
        scanf("%f", &tendered);
        change = tendered - sum;
        printf(" Change:\t\t%9.2f\n", change);
    }
}

---

Or even:

Code:

---

    else if( choice == 9  || choice == 10 )
    {
        for( i = 0; i < 8; ++i )
        {
            sum = 0;
            if( subtotals[i] > 0 )
                printf("\n%s:\t\t\t%9.2f",item[i],subtotals[i]);
            sum += subtotals[i];
        }
        printf("\n----------------------------------\n");
        printf(" Total:\t\t\t%9.2f\n", sum);
        printf("----------------------------------\n");
        if (choice == 10) {
              printf(" Tendered:\t\t");
          scanf("%f", &tendered);
          change = tendered - sum;
          printf(" Change:\t\t%9.2f\n", change);
        }
    }

---

That reduces the duplication a bit further, since both 9 and 10 do almost identical things.

Red shows typo fixed.

--
Mats

Quote:

---

Originally Posted by matsp

That reduces the duplication a bit further, since both 9 and 10 do almost identical things.

Red shows typo fixed.

--
Mats

---

Oops, I'll fix that. Like I said, untested...

matsp & hk_mp5kpdw: thats exactly what I'm doing right now... After i read IceDane's post and took a hard look at my code it just hit me: jeez, there's so much repetition in there... So, now Im trying to further optimize the code... I haven't studied or tested your code yet, since i wanna see how I get on doing it myself... seems quite simple in theory, but then again i thought the same about this whole project and been burnt quite a few times on the way...
Anyway, will get back to you when I'm done...

Quote:

---

Originally Posted by Karpaty

matsp & hk_mp5kpdw: thats exactly what I'm doing right now... After i read IceDane's post and took a hard look at my code it just hit me: jeez, there's so much repetition in there... So, now Im trying to further optimize the code... I haven't studied or tested your code yet, since i wanna see how I get on doing it myself... seems quite simple in theory, but then again i thought the same about this whole project and been burnt quite a few times on the way...
Anyway, will get back to you when I'm done...

---

Doing it yourself is the best way to KNOW that you [at least think] that you understand what's going on. Use the examples here only as a "last resort".

--
Mats

Great! I managed to get it working myself... Hooray!...
I even found a little misplaced assignment in the above code (yes, i realize you did not test the code prior posting it). I just thought i point it out for those who might find this code useful in the future. You assigned "0" to "sum" inside the FOR loop, so every time the loops repeats itself it overwrites the value of "sum" to "0".
In my "version" I moved the assignment statement just above the FOR loop line... Seems to produce the desired result :)

Anyway, thank you all who replied to this thread. It's been a wonderful learning experience. :D

P.S. last question, in my code i used i++ assignment in the FOR loop, you used ++i... What is the difference? Seems to be doing the same thing, doesn't it?

For standard integer types, i++ and ++i are identical [1].

In C++, where you can use ++ on "complex" data types, there is a slight difference in efficiency between x++ and ++x (giving the latter a small advantage), which means that some people use ++x. The main reason for this is that x++ require that you FIRST make a copy of the value, then increment it. The object itself doesn't have to be very big before this overhead of copying the object becomes noticable.

[1] Of course, this only applies if the x++ or ++x is "standalone" - if it's used inside an array index, or some such, there is of course a difference in that the ++x will FIRST increment the value, then be used as an index, whilst x++ will first be used as an index, THEN update the value.

--
Mats

Quote:

---

Originally Posted by Karpaty

I even found a little misplaced assignment in the above code (yes, i realize you did not test the code prior posting it). I just thought i point it out for those who might find this code useful in the future. You assigned "0" to "sum" inside the FOR loop, so every time the loops repeats itself it overwrites the value of "sum" to "0".
In my "version" I moved the assignment statement just above the FOR loop line... Seems to produce the desired result :)

---

Yep, good catch. I'll leave that in there for now, don't feel like changing it.

I've been trying to modify the code to be able to add a description to each item by adding a new string array called "description" and modifying the code a bit. However, its not as easy as I originally thought. Go figures... hehe

Note: the new code is in red

The first red line is the declaration of the string array for description.
The third red line asks the user to enter the description for items 1-8
This follows with the "gets" statement to get the value of the description. I used gets instead of "scanf" because the description might have spaces in there and "scanf" doesnt do spaces.
On the same line I also have [choice-1] - the reason for this is because I want to match the name and its description...
However, the problem is, that the gets() statement doesnt do what it supposed to do... The program skips it. I mean it does display "Description", but doesnt give me the chance to enter the description and goes straight to "Price"...
What am i doing wrong?

Code:

---

#include <stdio.h>
#define MENU 11
#define ITEMS 8

int main ( ) {

char item[MENU][20] = {" Bread", " Butt.", " Conf.",
                " Fruit", " Meat", " Milk", " Veg.",
                " Other", " Sub-total", "Total", "Quit"};
char description[ITEMS][20];
int i;
int choice;
float cost;
float sum, tendered, change;
float subtotals[ITEMS] = { 0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 0.0f };

while (choice != 11)
  {
    printf("\n Enter your choice:\n");
    for (i = 0; i < MENU; i++)
    {
        printf("\t&#37;d. %s\n", (i + 1), item[i]);
    }
    printf("\t\t--> ");
    scanf("%d", &choice);
    getchar();

    if(choice > 0 && choice < 9)
    {
        printf(" Description:\t\t");
        gets(description[choice-1]);
        printf(" Price:\t\t");
        scanf("%f", &cost);
        subtotals[choice-1] += cost;
    }
    else if(choice == 9)
    {
        sum = 0;
        for(i = 0; i < ITEMS; i++)
        {
            if(subtotals[i] > 0)
            {
                printf("\n%s: %s\t\t\t%9.2f", item[i], description[i], subtotals[i]);
                sum += subtotals[i];
            }
        }
        printf("\n----------------------------------\n");
        printf(" Total:\t\t\t%9.2f\n", sum);
        printf("----------------------------------\n");
    }
    else if(choice == 10)
    {
        sum = 0;
        for(i = 0; i < ITEMS; i++)
        {
            if(subtotals[i] > 0 )
            {
                printf("\n%s: %s\t\t\t%9.2f", item[i], description[i], subtotals[i]);
                sum += subtotals[i];
            }
        }
        printf("\n----------------------------------\n");
        printf(" Total:\t\t\t%9.2f\n", sum);
        printf("----------------------------------\n");
        printf(" Tendered:\t\t  ");
        scanf("%f", &tendered);
        change = tendered - sum;
        printf(" Change:\t\t%9.2f\n", change);
    }
  }
}

---

Don't use gets, use fgets instead. The previous scanf call is likely leaving the newline character in the input stream which may be read (is read) by later input operations, i.e. gets/fgets. gets sees this and thinks you tried to type something in followed by the newline/enter key. I think there is a FAQ entry on this.

Also, the way things work, you can loop through and enter in the same groups of food multiple times, you could pick Meat then Bread then Meat again for example, and each time doing that you'd be forced to enter a description that would overwrite the previous description entered. Is that what you want to do? And, when printing out the totals/subtotals, depending on the descriptions entered and their lengths, your formating of the prices may be off unless you do something about it.

Quote:

---

Originally Posted by hk_mp5kpdw

Don't use gets, use fgets instead. The previous scanf call is likely leaving the newline character in the input stream...

---

I think I can fix this problem by including the...

Code:

---

        getchar();

---

...line after the previous scanf() statement (see the edited code in the previous post)...

Quote:

---

Originally Posted by hk_mp5kpdw

Also, the way things work, you can loop through and enter in the same groups of food multiple times, you could pick Meat then Bread then Meat again for example, and each time doing that you'd be forced to enter a description that would overwrite the previous description entered. Is that what you want to do? And, when printing out the totals/subtotals, depending on the descriptions entered and their lengths, your formating of the prices may be off unless you do something about it.

---

Hmm, when you put it this way, it seems much harder than I thought. No, I do not want to overwrite any entry. I was thinking of grouping each entry for, lets say, bread and butter (and the rest), so you could have something like:

Code:

---

Bread:
  Whole bread white:        $1.50
  Whole bread brown:        $1.65
Butter:
  Type 1 butter:        $2.00
  Type 2 butter:        $2.15
------------------------------------------
TOTAL:                        $7.30

---

Hmm, i think my whole program would have to be completely rewritten...
I dont know whether im tired from coding all day, or just luck of knowledge (or both), but I, honestly, dont even know where to start...

Well, at the level that the rest of the code is, it is non-trivial to solve that.

The most obvious and simple solution is a three-dimensional array and a further variable to track the number of items per category that you've got so far [so you know how many items of bread has been purchased, for example].

The three-dimension array is a fine solution aside from using rather a lot of memory [because you get 8 * nitems * 20, or 160 * the number of items per category amount of memory - not a huge amount for a modern PC as long as you keep the number of items per category sort of sane - but if you want to keep up with a weekly shop for a family of 2 adults and three teenagers, you may end up with rather a large amount of types of bread, veg, fruit, etc].

The alternative is that you dynamically allocate memory for each category - for example using a linked list per category. But this is probably beyond the scope of your current level of knowledge/understanding.

--
Mats

Actually we did do the dynamic allocation of memory (malloc, calloc etc) last week, but we were told it was not essential for this particular assignment.
Im gonna try to do it anyway, since it seems 3-dimensional array is a bit too complicated for me at this stage...
I tried to write a simple program to see how this whole idea of 3D array would work, but unfortunatelly with not much luck...

Code:

---

#include <stdio.h>
#define ITEMS 8
#define DESCRIPTION 20
#define CHARACTERS 20

int main ( )
{
    char item[ITEMS][DESCRIPTION][CHARACTERS];
    int i, j;

    for (i = 0; i < ITEMS; i++)
    {
        printf("Enter the name of the item: ");
        gets(item[i]);
        for (j = 0; j < DESCRIPTION; j++)
        {
            printf("Enter the description: ");
            gets(item[i][j]);
        }
    }

    printf("ITEMS:\t\tDESCRIPTION:\n");
    for (i = 0; i < ITEMS; i++)
    {
        for (j = 0; j < DESCRIPTION; j++)
        {
            printf("&#37;s\t\t%s\n", item[i], item[i][j]);
        }
    }
}

---

Even without compiling I somehow knew there would be some problems with the red parts of the code, but after searching for a solutions for almost an hour, i gave up... Cant believe there are so few C programming 3D array examples out there...

Im gonna start working on "dynamic allocation" solution now and see how it goes...

First of all, don't use gets(), use fgets(), as the latter is safe, the former isn't.

[If your teacher says "use gets" you probably should consider also replacing the teacher with a safer one... ;)]

Your code looks mainly correct, but the red section is broken because you are using a gets() to read into a 2D array - which is definitely not impossible, just wrong!

The correct solution is two have a different array with the group description, e.g:

Code:

---

    char item[ITEMS][DESCRIPTION][CHARACTERS];
    char descr[ITEMS][CHARACTERS];
    int i, j;

    for (i = 0; i < ITEMS; i++)
    {
        printf("Enter the name of the item: ");
        gets(descr[i]);
        for (j = 0; j < DESCRIPTION; j++)
        {
            printf("Enter the description: ");
            gets(item[i][j]);
        }
    }

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I think you are capable of figuring how to print the same.

--
Mats

Quote:

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Originally Posted by matsp

[If your teacher says "use gets" you probably should consider also replacing the teacher with a safer one... ;)]

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Hehe, you noticed that didnt you? Yeah, we only did gets() at this point, so I was quite reluctant to jump ahead of myself, even though everyone around said fgets() is better.
Thank you as always... Will work on that... :)