Any help much appreciated

I have been asked to write a program that will ask the user to enter two months, and then give the number of days from the start of the first month to the end of the second. I have very little experience with programming and i'm struggling with this one...
Please do not flame me, i am not asking anyone to do this for me, but if you could give me a push in the right direction it would be much appreciated.

The main problem i am having is trying to figure out how to do the actual working out.. The number of days in each month is to be stored in an array, numDays, am i right in thinking that i'll have to use ++ in some way? I am really stuck with this, any help at all would be great.

Here is what i have so far... It isn't even half done yet, i know that its a big mess but pls bear in mind i am a total programming n00b..

I have no idea where to put the array, i realise its probably not meant to go there....
The 'if' statement will almost certainly not work, it was a stab in the dark...
I'm sure i've either got too many variables or else they arn't defined very well...

Take pity on me?

Code:

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#include <stdio.h>

int main()
{
    int fromMonth, toMonth;
   
    printf ("This program will tell you the number of days from the start of one month to the end of another\n");
    printf ("Enter the nmumber of the months you wish to use (Jan=1, Feb=2 etc..): ");
    scanf ("%d", &fromMonth );
    scanf ("%d", &toMonth );
    printf ("The total number of days is %d\n", howManyDays( fromMonth, toMonth ) );
    return 0;
}

int howManyDays (int fromMonth, int toMonth)
{
    if fromMonth < 1, > 12, if toMonth < 1, > 12
    printf ("Error: Please check the input..\n");
    howManyDays = numDays [fromMonth]
   
   
    int numDays[12];
    $numDays [1]=31;
    $numDays [2]=28;
    $numDays [3]=31;
    $numDays [4]=30;
    $numDays [5]=31;
    $numDays [6]=30;
    $numDays [7]=31;
    $numDays [8]=31;
    $numDays [9]=30;
    $numDays [10]=31;
    $numDays [11]=30;
    $numDays [12]=31;

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first thing, arrays start at 0 not 1. so with

Code:

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int numDays[12]

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the identifiers are actually 0-11.

You can also merge the 2 scanf()s together:

Code:

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scanf("%d%d", &fromMonth, &toMonth)

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I personally have never seen if statements like the ones in your code. An if statement should be in the following format:

Code:

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if (expression)
    statement

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Please note that the statement can be a compound statement sorrounded by brackets

thanks a lot for the help

To calculate the result, could i use a for statement? something like for (fromMonth <= toMonth then some sort of ++ thing... but then im not sure how that would call and add the days for each month... I think i'm just not cut out for this stuff ...

Yes, a for-loop woudl work quite well.

--
Mats

Oh ya. Another thing is that you can initialize the array like this:

Code:

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int numDays[12] = {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};

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And your howManyDays() function should look like this:

Code:

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int
if (fromMonth < 0 || fromMonth > 11 || toMonth < 0 || toMonth > 11)
  printf("Error. Please check the input...\n");
else
{
  int numDays[12] = {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
  int count, result=0;

  for (count=fromMonth; count <= toMonth; count++)
      result += numDays[count];

  return result;

---

And since arrays start from 0 you should either make Jan=0, Feb=1... or after inputting the data just deduct 1 from the two variables.

thanks, you're life savers, I would really be stuck without the help.

Could someone give me a hint as to why this isn't compiling? I get told that the are 'too many arguments to function howManyDays'. I cant see what i'm doing wrong, i've checked all the online guides i can and it looks to me like im doing the right thing (although im clearly not).

As always, i'm thankful for any help

Code:

---

#include <stdio.h>

int howManyDays ( int result );  //declare numDays function
 
int main ()  //Start of main function
{
    int toMonth, fromMonth;
    int numDays[12] = {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
   
    printf ("This program will tell you the number of days from the start of one month to the end of another\n");
    printf ("Enter the nmumber of the months you wish to use (Jan=1, Feb=2 etc..): ");
    scanf("%d%d", &fromMonth, &toMonth);
    printf ("The total number of days is %d\n", howManyDays( fromMonth, toMonth ) );   // sends values for from/toMonth to numDays
    return 0;
}  //main function ends

int howManyDays( fromMonth, toMonth ) {      //numDays function
if (fromMonth < 0 || fromMonth > 11 || toMonth < 0 || toMonth > 11)
  printf("Error [-1]. Please check the input...\n");
else
{
  int numDays[12] = {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
  int count, result=0;

  for (count=fromMonth; count <= toMonth; count++)
      result += numDays[count];

  return result;              //result sent to main
}

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Code:

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int howManyDays( fromMonth, toMonth ) {      //numDays function

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->

Code:

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int howManyDays( int fromMonth, int toMonth ) {      //numDays function

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Also, you declare this in main()

Code:

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int numDays[12] = {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};

---

but never use it. In addition, in howManyDays() where you also declare it, you can leave out the "12" for the size if you like, and the compiler will calculate the number of elements in the array for you.

Also, your code has January as 0, Feb. as 1, etc, but you print

Code:

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Enter the nmumber of the months you wish to use (Jan=1, Feb=2 etc..):

---

thanks :D

I've made those changes, but i'm still getting the ' too many arguments to function `howManyDays' ' error, any ideas?

ahhh think i got it, its compiled now at least

Code:

---

#include <stdio.h>

int howManyDays (  int fromMonth, int toMonth  );  //declare numDays function
 
int main ()  //Start of main function
{
    int toMonth, fromMonth;
   
    printf ("This program will tell you the number of days from the start of one month to the end of another\n");
    printf ("Enter the nmumber of the months you wish to use (Jan=0, Feb=1 etc..): ");
    scanf("%d%d", &fromMonth, &toMonth);
    printf ("The total number of days is %d\n", howManyDays( fromMonth, toMonth ) );  // sends values for from/toMonth to numDays
    return 0;
}  //main function ends



int howManyDays( int fromMonth, int toMonth ) {      //numDays function

    int numDays[12] = {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
if (fromMonth < 0 || fromMonth > 11 || toMonth < 0 || toMonth > 11)
  printf("Error [-1]. Please check the input...\n");
else
{
  int count, result=0;

  for (count=fromMonth; count <= toMonth; count++)
      result += numDays[count];

  return result;              //result sent to main
}
}

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Very good . . . just one thing: what happens just after you print "Error [-1]. ..."? What does howManyDays() return? A random value.

You probably want to return -1 or 0 or something in this case.

Oh, and what about leap years? ;)

Quote:

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Originally Posted by euclid

ahhh think i got it, its compiled now at least

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Yes, make sure your declarations and definitions of function are one and the same! They should be equal, or you will get compile errors or linking errors.

You could also use an enum to declare your months, instead of having arrays..

thanks for all the help, this is the finished code, which now tests itself and prints out the results..

Code:

---

#include <stdio.h>

int howManyDays (  int fromMonth, int toMonth  );  //declare numDays function
 
int main ()  //Start of main function
{
    int toMonth, fromMonth, i, j;
   
        for (i = 0; i < 12; i++)
                for (j = 0; j < 12; j++)
                printf ("%d\n", howManyDays(i, j));

    printf ("This program will tell you the number of days from the start of one month to the end of another\n");
    printf ("Enter the nmumber of the months you wish to use (Jan=0, Feb=1 etc..): ");
    scanf("%d %d", &fromMonth, &toMonth);    //user enters 2 months
    printf ("The total number of days is %d\n", howManyDays( fromMonth, toMonth ) );  // sends values for from/toMonth to numDays
    return 0;
}  //main function ends



int howManyDays( int fromMonth, int toMonth ) {      //numDays function
        int count, result=0;
    int numDays[12] = {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};  //array declared
        if (fromMonth < 0 || fromMonth > 11 || toMonth < 0 || toMonth > 11) {
  printf("Error [-1]. Please check the input..\n");
        return 0;
        } else
{
  for (count=fromMonth; count <= toMonth; count++)
      result += numDays[count];

  return result;              //result sent to main
}
}

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