Thread: Function problems

This is my first time on this board, and I already like it. I have been having trouble making functions work for the last several months, and this function confuses me to no ends.

The goal of the project is to force the computer to print a digit out of asterisks, something like this:

Code:

  
  *******
        *
        *
  *******
        *
        *
  *******

In case you are like me, and couldn't see it at first, this is a 3. The project is supposed to build on two previously made functions, printBox, and printStars, but I do not see how it does. I will also include the program I built for those functions. It is supposed to be called printDigit. Here is the code I have so far. I think I have the call and headers correct, but do not know how I should make this function work.

Code:

#include <stdio.h>
#include <stdlib.h>
void printDigit(int, int);
main(void)
{
 int a,b;
 printf("Input 2 numbers. The first number is the number you wish to form.\n
             The second number will determine the size of the digit printed.");
 scanf("%d %d",&a,&b);
 void printDigit(int a, int b);
}

void printDigit(int a, int b)
{

Code:

#include <stdio.h>

main()
{
  void printBox(int length, int height);

  printf("A 3x5 box:\n");
  printBox(5, 3);
  printf("\n");
  printf("A 5x10 box:\n");
  printBox(10, 5);
  return 0;
  system("pause");
}

void printAsterisks(int n)
{
  int i;

  for (i=0;i<n;i++)
    printf("*");
}

void printBlanks(int n)
{
  int i;

  for (i=0;i<n;i++)
    printf(" ");
}

void printBox(int length, int height)
{
  void printAsterisks(int n);
  void printBlanks(int n);

  int i;
  if (height >= 1)
   printAsterisks(length);
   printf("\n");
    for (i=1;i<height-1;i++)
    {
      if (length >= 1)
       printf("*");
	  if (length >= 2)
      printBlanks(length - 2);
      printf("*");
	}
     printf("\n");      
     if (height >= 2)
     printAsterisks(length);  
     printf("\n");
}

Any help would be appreciated, as this project was due yesterday.

OK, so a few notes:
1) Main returns int.
2) Prototypes should be in a separate header file or at the start of your source file, bot inside functions.
3) You might need to indent a little better: http://cpwiki.sf.net/User:Elysia/Indentation.
4) 1 space for indentation which you use in some places is hardly enough.
5) It might be better to use getchar() instead of system("pause") due to being more portable.

And you never actually mentioned what the problem was?

Originally Posted by Elysia

OK, so a few notes:
1) Main returns int.

To elaborate: cpwiki.sf.net/Void_main

2) Prototypes should be in a separate header file or at the start of your source file, [n]ot inside functions.

Well, they don't have to be -- and I wouldn't even go so far to say that they "should" be. I'd just state that by convention, prototypes are declared globally, often at the beginning of the source file; after #includes but before any function bodies. But at least one book that I've seen used the local-prototype style, and it's perfectly acceptable. At least prototypes are being used.

I know we've had this discussion before . . . .

3) You might need to indent a little better: http://cpwiki.sf.net/User:Elysia/Indentation.

Those two pages really ought to be merged . . . .

5) It might be better to use getchar() instead of system("pause") due to being more portable.

cpwiki.sf.net/Pause_console

Anyway.

I'm not sure exactly what you need to do to get this

Code:

  *******
        *
        *
  *******
        *
        *
  *******

but you could just consider it a series of

Code:

  *******

and

Code:

        *

I'm sure that's occured to you. Perhaps it would be better to consider it to consist of two semi-boxes:

Code:

  *******
        *
        *

and one filled-in line:

Code:

  *******

(Are those spaces at the beginning of the lines intentional?)

Or maybe even one big box, minus the left side, which is intersected in the middle.

Originally Posted by dwks

To elaborate: cpwiki.sf.net/Void_main

But this is implicit main, not void main...

Well, they don't have to be -- and I wouldn't even go so far to say that they "should" be. I'd just state that by convention, prototypes are declared globally, often at the beginning of the source file; after #includes but before any function bodies. But at least one book that I've seen used the local-prototype style, and it's perfectly acceptable. At least prototypes are being used.

I know we've had this discussion before . . . .

Indeed. Local function declarations are stupid because it clutters up the code and it creates duplicates of function prototypes and it means the functions can't be used in other source files, unless you duplicate them.
I consider it bad practice to put them locally.

Those two pages really ought to be merged . . . .

You said you were going to try it. What happened?

Originally Posted by Elysia

But this is implicit main, not void main...

Oh, you're right -- I thought implicit main was explained there as well.

You said you were going to try it. What happened?

I think you're getting a PM on the subject in a little while . . . .

Originally Posted by dwks

Oh, you're right -- I thought implicit main was explained there as well.

Well, it mentions it should say "int main()" but nothing really apart from that. It only covers void main.

OK well, prototypes aren't variables and should be on file scope level. It's good practice. In real applications, you're going to use headers. And then the prototypes are typically always global.
Your professor doesn't have a problem with function prototypes, or...?
Well, suppose you could try and if your professor throws a fit, make it local but remember the little advice when you graduate.

The textbox sums it up very well. You need to think about how to you would do it in reality.
Try cluttering on a paper or something. Find a logical solution to the problem. That's the first step. Then you write the code.

This is not a trivial assignment, unless I'm missing the obvious. Either that or all the constraints weren't put forth. Per my understanding, this program has to be able to draw the character-art representation of numbers 0-9 to an undefined scale.

Therefore, it doesn't make sense to hard-code the representation of the numbers, and that leaves coming up with algorithms, for each digit, to be able to scale it with a random grid.

What am I missing?

getchar() isn't a portable function either...

hmm... are you trying to say that nothing is absolutely portable? Elysia noted that it was "more portable", and this seems reasonable since getchar() is part of the C standard library.

Originally Posted by brewbuck

Having no specified return type is the same as specifying "int."

Irrelevant. All functions should specify a return type. Leaving it out is just bad practice.

Originally Posted by Elysia

Irrelevant. All functions should specify a return type. Leaving it out is just bad practice.

Indeed - if you leave it out, it is very hard to know if it was left out by mistake or if it was left out on purpose. If it's there, there is no confusion about what it is. In some respects, I think the same about (void) in function the function argument list in C++.

--
Mats