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Help with FUNCTION LOGIC and ARGUMENTS--C Programming

Posted on 2006-07-19
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Last Modified: 2010-04-15
I'm seeking help with a specific problem I'm having with a program I wrote that displays a menu and uses functions to calculate results based on a user's entries. I have 4 functions that add, multiply, divide and subtract, but they are not working exactly right and I not sure what's wrong. I'm also not correctly getting user input. Could someone review my code and enlighten me about my mistakes?

Thanks very much in advance.

----------------------------------------HERE IS MY CODE----------------------------------------------

#include <stdio.h>
char get_choice(void);
char get_first(void);
float get_float(void);
float add();
float divide();
float multiply();
float subtract();
int main(void)
{
    int choice;
   
    while ( (choice = get_choice()) != 'q') //compare choice to 'q' terminator
    {
        switch (choice)
        {
            case 'a' :  add();
                        break;
            case 'd' :  divide();
                        break;
            case 'm' :  multiply();
                        break;
            case 's' :  subtract();
                        break;
            default  :  printf("Program error!\n");
                        break;
        }
    }
    printf("See ya' later alligator!\n");
   
    return 0;
}

    float add() //function 1 (add two numbers)
{
    float sum = 0;
    float n,i;

    printf("Enter first number: ");
    printf("Enter second number: ");
    n = get_float();
    for (i = 1; i <= n; i++)
        printf("%f\n", i);
        sum == n + n;
    while ( getchar() != '\n') //get response, compare to \n
        continue; //skip rest of line
       
    return sum;
}
    float divide() //function 2 (divide two numbers)
{
    float quotient = 0;
    float n,i;

    printf("Enter first number: ");
    printf("Enter second number: ");
    n = get_float();
    for (i = 1; i <= n; i++)
        printf("%f\n", i);
        quotient == n / n;
       
    while ( getchar() != '\n') //get response, compare to \n
        continue; //skip rest of line
       
    return quotient;
}

    float multiply() //function 3 (multiply two numbers)
{
    float product = 0;
    float n,i;

    printf("Enter first number: ");
    printf("Enter second number: ");
    n = get_float();
    for (i = 1; i <= n; i++)
        printf("%f\n", i);
        product == n * n;
    while ( getchar() != '\n') //get response, compare to \n
        continue; //skip rest of line
       
    return product;
}
    float subtract() //function 4 (subtract two numbers)
{
    float difference = 0;
    float n,i;

    printf("Enter first number:\n");
    printf("Enter second number:\n");
    n = get_float();
    for (i = 1; i <= n; i++)
        printf("%f\n", i);
        difference == n - n;
    while ( getchar() != '\n') //get response, compare to \n
        continue; //skip rest of line
       
        return difference;
}
char get_choice(void) //function 5 (get_choice)
{
    float ch;

    printf("Enter the letter for the operation of your choice:\n");
    printf("a. ADD              s. SUBTRACT\n");
    printf("m. MULTIPLY         d. DIVIDE\n");
    printf("q. QUIT\n");
   
    ch = get_first();  //validate user input
    while (  (ch < 'a' || ch > 's') && ch != 'q')
    {
        printf("Please respond with a, d, m, s, or q.\n");
        ch = get_first();
    }
   
    return ch;
}

char get_first(void) //function 6 (get_first letter)
{
    int ch;

    ch = getchar();
    while (getchar() != '\n') //get response, compare to \n
        continue;
       
    return ch;
}

float get_float(void) //function 7 (get float)
{
    float input;
    char ch;
   
    while (scanf("%f", &input) != 1)
    {
        while ((ch = getchar()) != '\n') //get response, compare to \n
            putchar(ch);  // dispose of bad input
        printf("Please enter a number, such as 2.5, -1.78E8, or 3: ");
    }
   
    return input;
}
0
Comment
Question by:computerese
3 Comments
 
LVL 16

Assisted Solution

by:PaulCaswell
PaulCaswell earned 125 total points
ID: 17142035
Hi computerese,

There are several problem here.

1.             case 'a' :  add();

You are callint the 'add' function but you are not saving or using the result. Try something like:

    int choice;
    float result; // <<< Add this

Then use:

            case 'a' :  result = add(); // << Do this for all cases.

And after the case statement, something like:

 printf("Result is %f\n", result);

2.         sum == n + n;

This is not doing what you meant it to do. Look at it carefully! :-) There are several others like this.


Paul
0
 
LVL 8

Assisted Solution

by:manish_regmi
manish_regmi earned 125 total points
ID: 17143077
some of i found:

if you are returning just 1 float just doing this is fine

float get_float(void) //function 7 (get float)
{
    float input;
    char ch;
   
    scanf("%f", &input);
    return input;
}

  float add() //function 1 (add two numbers)
{
    float sum = 0;
    float n,i;

    printf("Enter first number: ");
    printf("Enter second number: ");
    n = get_float();
   i = get_float()
 
  sum = i + n;
    return sum;
}

similarly do as i have done in add to substract, multiply and divide.

regards
Manish Regmi
0
 
LVL 7

Accepted Solution

by:
nafis_devlpr earned 250 total points
ID: 17144637
there are several, most of them are logical, you should change the get float method in the following way


float get_float(void) //function 7 (get float)
{
    float input;
   
    while (scanf("%f", &input) != 1)
     {
         printf("Please enter a number, such as 2.5, -1.78E8, or 3: ");
         fflush(stdin);
      }
   
    return input;
}

now comes the error detection, the errors are almost same in all the function, i am showing you the add and divide function, change the other functions accordingly

float add() //function 1 (add two numbers)
{
    float sum = 0;
    float n,i;

    printf("Enter first number: ");
    printf("Enter second number: ");//<<------------------------------error
    n = get_float();
    for (i = 1; i <= n; i++)//<<------------------------------error
        printf("%f\n", i);
        sum == n + n;//<<------------------------------error
    while ( getchar() != '\n') //get response, compare to \n
        continue; //skip rest of line
       
    return sum;
}
    float divide() //function 2 (divide two numbers)
{
    float quotient = 0;
    float n,i;

    printf("Enter first number: ");
    printf("Enter second number: ");//<<------------------------------error
    n = get_float();//<<------------------------------error
    for (i = 1; i <= n; i++)//<<------------------------------error
        printf("%f\n", i);
        quotient == n / n;//<<------------------------------error
       
    while ( getchar() != '\n') //get response, compare to \n
        continue; //skip rest of line
       
    return quotient;
}


you should change the functions in the following way

float add() //function 1 (add two numbers)
{
    float sum = 0;
    float n;

    printf("Enter first number: ");
    sum = get_float();
    printf("Enter second number: ");
    sum += get_float();        
    return sum;
}

    float divide() //function 2 (divide two numbers)
{
    float quotient = 0;
    float n;

    printf("Enter first number: ");
    n = get_float();
    printf("Enter second number: ");
     quotient = get_float();
    while(quotient == 0.0)
      {
         printf("divisor cant be zero\nEnter second number: ");
         quotient = get_float();
       }
   
      quotient = n / quotient;
    return quotient;
}


there are some more errors in the get_first() and get_choice() function, change them into following

char get_choice(void) //function 5 (get_choice)
{
    char ch;

    printf("Enter the letter for the operation of your choice:\n");
    printf("a. ADD              s. SUBTRACT\n");
    printf("m. MULTIPLY         d. DIVIDE\n");
    printf("q. QUIT\n");
   
    ch = get_first();  //validate user input
   //while (  (ch < 'a' || ch > 's') && ch != 'q')  this will accept anything inside a to s as a valid input like 'b' or 'c'
    while (  ch != 'a' && ch != 's' && ch != 'm' && ch != 'd' && ch != 'q')
    {
        printf("Please respond with a, d, m, s, or q.\n");
        ch = get_first();
    }
   
    return ch;
}

char get_first(void) //function 6 (get_first letter)
{
    char ch;

    scanf("%c", &ch)
    fflush(stdin);
       
    return ch;
}

Hope this helps

Nafis
0

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