function calls and pointers

This is a discussion on function calls and pointers within the C Programming forums, part of the General Programming Boards category; I got this compiling but I'm getting no values in my output. Can anyone help out and tell me what ...

  1. #1
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    function calls and pointers

    I got this compiling but I'm getting no values in my output. Can anyone help out and tell me what I'm doing wrong.
    Code:
     
    #include <stdio.h>
    #include <time.h>
    #define SIZE 5
    
    /* function prototypes */
    double convert(int money);
    
    int main()
    {
       /* variable and array declarations */
       int money;
       srand( time(NULL));
       
       float xchange[] = { 1.00, 1.3593, 1.0013, 83.1300, 1.5837, rand(time)%100 };
          
    	/*
    	 * As of January 30, 2011, the current exchange values from www.google.com/finance.
    	 * USD (United States Dollar) = 1.00
    	 * EUR (Euro Dollar) = 1.3593
    	 * CAD (Canadian Dollar) = 1.0013
    	 * JPY (Japanese Yen) = 83.1300
    	 * GBP (Great Britian Pound) = 1.5837
    	 * DDS (Davidian Dollar Standard) = 3.56
    	 */
    
       /* prompt the user to enter a US dollar amount */
       printf( "Please enter the number of US dollar to be converted:\n" );
       scanf("%d.2f", money);
    
    	convert(money); /* function call */
    
    return 0; /* indicates successfull termination */
    } /* end main function */
    
    /* function prototypes */
    double convert(int money)
    
    {
    
       int *Ptr0, *Ptr1, *Ptr2, *Ptr3, *Ptr4, *Ptr5;
       int USD, EUR, CAD, JPY, GBP, DDS;
       Ptr0 = &USD;
       Ptr1 = &EUR;
       Ptr2 = &CAD;
       Ptr3 = &JPY;
       Ptr4 = &GBP;
       Ptr5 = &DDS;
    
       /* print the converted foreign currencies to the screen */
       *Ptr0 = 1.00 * money; /* USD */
       printf( "The total amount in US dollars: %8.2f\n", &USD);
    
       *Ptr1 = 1.3593 * money; /* EUR */
       printf( "The total amount in Euro dollars: %8.2f\n", &EUR);
    
       *Ptr2 = 1.0013 * money; /* CAD */
       printf( "The total amount in Canadian dollars: %8.2f\n", &CAD);
    
       *Ptr3 = 83.1300 * money; /* JPY */
       printf( "The total amount in Japanese Yen: %8.2f\n", &JPY);
    
       *Ptr4 = 1.5837 * money; /* GBP */
       printf( "The total amount in British Pounds: %8.2f\n", &GBP);
    
       *Ptr5 = rand(time)%100 * money; /* DDS */
       printf( "The total amount in Davidian dollars: %8.2f\n", &DDS);
    
    return 0; /* indicates successful termination */
    } /* end function money */
    Code:
    My output:
    
    
    Please enter the number of US dollar to be converted:
    1
    The total amount in US dollars:     0.00
    The total amount in Euro dollars:     0.00
    The total amount in Canadian dollars:     0.00
    The total amount in Japanese Yen:     0.00
    The total amount in British Pounds:     0.00
    The total amount in Davidian dollars:     0.00
    Last edited by davidjg; 01-30-2011 at 08:46 PM.

  2. #2
    cph
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    any problems?

  3. #3
    ... kermit's Avatar
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    Code:
    /* function prototypes */
    void currency ( int *Ptr)
    {
       /* Do something here */
    }
    
    double convert(int money)
    
    {
    
       int *Ptr0, *Ptr1, *Ptr2, *Ptr3, *Ptr4, *Ptr5;
    Edit: Since you edited your post, now I have to edit mine... Basically, what you asked about initially should get fixed if you do something similar to what I showed in the above code. Now you just have to deal with all the other problems.
    Last edited by kermit; 01-30-2011 at 08:44 PM.

  4. #4
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    Sorry for editing so quickly and thanks for your reply. I got it compiling but I can't seem to get the function call to read the values from the array in main. Any ideas on what to do here?

  5. #5
    and the Hat of Guessing tabstop's Avatar
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    You'll have to pass that array to your function, just like you passed the input value money into your function.

  6. #6
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    @tabstop.....I totally agree but how would I do that?

  7. #7
    and the Hat of Guessing tabstop's Avatar
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    The same way you passed your variable "money" to the function.

  8. #8
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    I'm just a C newb. The way that moeny was passed is through a function call "convert(money);" Can you provide an example on how I would pass the values of the array into the function? Help please!

  9. #9
    and the Hat of Guessing tabstop's Avatar
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    convert(money, other_things, those_things_over_here, change_under_the_sofa_cushions)

  10. #10
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    Ok.......it's still giving me no value in the output. Any ideas on what to do here?

    convert(money); /* function call */
    convert(xChange); /* function call */



    Please enter the number of US dollars to be converted:
    1
    The total amount in US dollars: 0.00
    The total amount in Euro dollars: 0.00
    The total amount in Canadian dollars: 0.00
    The total amount in Japanese Yen: 0.00
    The total amount in British Pounds: 0.00
    The total amount in Davidian dollars: 0.00
    The total amount in US dollars: 0.00
    The total amount in Euro dollars: 0.00
    The total amount in Canadian dollars: 0.00
    The total amount in Japanese Yen: 0.00
    The total amount in British Pounds: 0.00
    The total amount in Davidian dollars: 0.00

  11. #11
    -bleh-
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    Of course it will be all 0 because your function return nothing but "0"
    Code:
    return 0; /* indicates successful termination */
    the prototype for convert should be
    Code:
    /* function prototypes */
    double convert(int money,int * somearray)
    then write to that array instead of writing to all those local unallocated pointers.
    Last edited by nimitzhunter; 01-30-2011 at 10:04 PM.
    "All that we see or seem
    Is but a dream within a dream." - Poe

  12. #12
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    Ok....I modified the prototype....but now getting compiler errors again.

    currency1.c: In function `main':
    currency1.c:39: too few arguments to function `convert'
    currency1.c:40: warning: passing arg 1 of `convert' makes integer from pointer without a cast
    currency1.c:40: too few arguments to function `convert'


    Code:
    #include <stdio.h>
    #include <time.h>
    #define SIZE 5
    
    /* function prototypes */
    double convert(int money, int * xchange);
    
    int main()
    {
       /* variable and array declarations */
       int money;
       srand( time(NULL));
       
       float xchange[] = { 1.00, 1.3593, 1.0013, 83.1300, 1.5837, rand(time)%100 };
          
    	/*
    	 * As of January 30, 2011, the current exchange values from www.google.com/finance.
    	 * USD (United States Dollar) = 1.00
    	 * EUR (Euro Dollar) = 1.3593
    	 * CAD (Canadian Dollar) = 1.0013
    	 * JPY (Japanese Yen) = 83.1300
    	 * GBP (Great Britian Pound) = 1.5837
    	 * DDS (Davidian Dollar Standard) = 3.56
    	 */
    
       /* prompt the user to enter a US dollar amount */
       printf( "Please enter the number of US dollars to be converted:\n" );
       scanf("%d.2f", money);
    
    	convert(money); /* function call */
    	convert(xchange); /* function call */
    
    //return 0; /* indicates successfull termination */
    } /* end main function */
    
    /* function prototypes */
    double convert(int money, int * xchange)
    
    {
    
       int *Ptr0, *Ptr1, *Ptr2, *Ptr3, *Ptr4, *Ptr5;
       int USD, EUR, CAD, JPY, GBP, DDS;
       Ptr0 = &USD;
       Ptr1 = &EUR;
       Ptr2 = &CAD;
       Ptr3 = &JPY;
       Ptr4 = &GBP;
       Ptr5 = &DDS;
    
       /* print the converted foreign currencies to the screen */
       *Ptr0 = 1.00 * money; /* USD */
       printf( "The total amount in US dollars: %8.2f\n", xchange);
    
       *Ptr1 = 1.3593 * money; /* EUR */
       printf( "The total amount in Euro dollars: %8.2f\n", xchange);
    
       *Ptr2 = 1.0013 * money; /* CAD */
       printf( "The total amount in Canadian dollars: %8.2f\n", xchange);
    
       *Ptr3 = 83.1300 * money; /* JPY */
       printf( "The total amount in Japanese Yen: %8.2f\n", xchange);
    
       *Ptr4 = 1.5837 * money; /* GBP */
       printf( "The total amount in British Pounds: %8.2f\n", xchange);
    
       *Ptr5 = rand(time)%100 * money; /* DDS */
       printf( "The total amount in Davidian dollars: %8.2f\n", xchange);
    
    return 0; /* indicates successful termination */
    } /* end function money */

  13. #13
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    Please help......!!!

  14. #14
    -bleh-
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    Code:
    int main()
    {
    ...
    // money has to be type float. 
    convert(money,xchange); /* function call */
    ...
    }
    that function doesn't have to return
    Code:
    void convert(float money, const int * xchange)
    {
    
       /* print the converted foreign currencies to the screen */
       printf( "The total amount in US dollars: %8.2f\n", xchange[0]*money);
       // you do the rest of them
    } /* end function money */
    "All that we see or seem
    Is but a dream within a dream." - Poe

  15. #15
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    Thanks to all who helped me on this project.

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